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Thyrotropin-releasing hormone (TRH) and its analogs have a number of neurobiological functions and therapeutic uses in disorders of the central nervous system. In this study, the newly synthesized TRH analogs were evaluated for central nervous system activity in pentobarbital-induced sleeping in mice. The most potent TRH analog (L-pGlu-(2-propyl)-L-His-L-ProNH(2) coded as NP-647) was evaluated for its antiepileptic potential in various seizure models in mice in comparison with TRH. Intravenous pretreatment with NP-647 (10 and 20 micromol/kg body wt) significantly delayed the onset and reduced the frequency of convulsions in the pentylenetetrazole model, but not in the maximum electroshock seizure model. Also, it was found to be protective against picrotoxin- and kainic acid-induced seizures. However, NP-647 did not significantly affect theophylline-induced seizures. Further study of the effect of NP-647 on locomotor activity and a functional observational battery revealed that it did not significantly exhibit any undesirable effects as compared with vehicle and TRH. NP-647 did not significantly affect cerebral blood flow, whereas the native peptide TRH markedly increased cerebral blood flow. Furthermore, NP-647 exerted antiepileptic activity without significantly altering plasma thyroid-stimulating hormone levels and mean arterial blood pressure. This suggests that NP-647 is more selective for central nervous system activity and devoid of hormonal and cerebrovascular system effects. In contrast, TRH exhibited cardiac and endocrine effects as marked by significant elevation in mean arterial blood pressure and plasma thyroid-stimulating hormone levels. This study demonstrates that NP-647 has potential antiepileptic activity devoid of undesirable effects and, thus, can be exploited for the prevention and treatment of epilepsy.

Perinatal and postnatal study of taltirelin hydrate, a thyrotropin releasing hormone analogue, was carried out in Sprague-Dawley rats. Female rats were given taltirelin hydrate at a dose of 0 (control), 0.15, 1.5, or 15 mg/kg from day 17 of gestation to day 20 after delivery. All pregnant rats were allowed to deliver spontaneously and their offspring were examined. In the 15 mg/kg group, the dams showed the central nervous effects such as wet dog shaking during gestation periods. No adverse effect of taltirelin hydrate on the body weight gain, food consumption and reproductive performance was observed in this group. In the 0.15 and 1.5 mg/kg groups, the drug did not have any adverse effects. Taltirelin hydrate did not have any adverse effects on viability, growth, physical differentiation, functional and behavioral development (coordinated activity, auditory function, emotionality, learning ability, and spontaneous motor activity), and reproductive performance of F1 offspring, and development of F2 fetuses. These results show that the no-toxic dose levels of taltirelin hydrate are 1.5 mg/kg for general toxicity in dams, and 15 mg/kg for reproductive function of dams and for their offspring.

Oncogenicity studies of taltirelin tetrahydrate (TA-0910), a new thyrotropin-releasing hormone (TRH) analogue, were carried out on CD-1 mice and CD rats. Groups of 60 male and 60 female CD-1 mice received TA-0910, by oral gavage, at dosages of 5, 15 or 50 mg/kg/day. Treatment continued for a minimum period of 104 weeks. Groups of 55 male and 55 female CD rats received TA-0910, by oral gavage, at dosages of 20, 60 or 200 mg/kg/day. Treatment continued for a minimum period of 90 or 94 weeks for males and females, respectively. Of the treatment-related behavioral changes noted, the majority were considered to be directly related to the known pharmacological activity of the test substance and, as such, to be of questionable direct toxicological significance. In mice, there was no evidence of a treatment-related effect on the incidence of neoplasms. In rats, slightly higher incidences of pituitary adenoma, in males given 60 or 200 mg/kg/day, and thyroid follicular adenoma, in females given 200 mg/kg/day, were noted. However, in neither case was statistical significance attained in pair-wise comparisons, and the incidences were within expectation from background data. There was no evidence of any oncogenic potential of TA-0910 in these studies.

Fertility study of taltirelin hydrate, a thyrotropin releasing hormone analogue, was carried out in Wistar rats. Taltirelin hydrate was orally administrated at a dose of 0 (control), 0.15, 1.5, or 15 mg/kg. Male rats were given the drug from 63 days before mating to the day before autopsy (total of 121 days), and female rats were treated from 14 days before mating to day 7 of gestation. The females were sacrificed on day 21 of gestation and pregnancy outcome was determined. In the 15 mg/kg group, wet dog shaking behavior and hyperlocomotion were observed in males and females, and the food consumption was slightly decreased in male rats. These changes induced by taltirelin hydrate were not found in the 0.15 and 1.5 mg/kg groups. No adverse effects of taltirelin hydrate on reproductive function were detected in any groups. In the fetal examination, taltirelin hydrate had no teratogenic, lethal, or growth retardation effects in any groups. These results show that the no-toxic dose levels of taltirelin hydrate are 1.5 mg/kg for general toxicity in parent animals, and 15 mg/kg for reproductive function of parent animals and for development of their fetuses.

Teratogenicity study of taltirelin hydrate, a thyrotropin releasing hormone analogue, was carried out in Wistar rats. Female rats were orally given taltirelin hydrate at a dose of 0 (control), 0.15, 1.5, or 15 mg/kg from day 7 to day 17 of gestation. Twenty-seven female rats in each group were sacrificed on day 21 of gestation and their fetuses were examined. The remaining 13 female rats in each group were allowed to deliver spontaneously and their newborns were examined. In the 15 mg/kg group, the dams (P) showed wet dog shaking behavior and hyperlocomotion. No adverse effect of taltirelin hydrate on the body weight gain, food consumption, water intake, and reproductive performance was observed in this group. In the 0.15 and 1.5 mg/kg groups, taltirelin hydrate did not show any adverse effects. In F1 generation groups, taltirelin hydrate had no teratogenic, lethal, or growth retardation effects in any groups. There were also no adverse effects of taltirelin hydrate on postnatal development, emotionality, coordinated activity, sensitivity, learning ability, and reproductive performance of F1 offspring, and development of F2 fetuses. These results show that the no-toxic dose levels of taltirelin hydrate are 1.5 mg/kg for general toxicity in dams, and 15 mg/kg for reproductive function of dams (P) and for development of F1 generation.

Teratogenicity study of taltirelin hydrate, a thyrotropin releasing hormone analogue, was carried out in Japanese white rabbits. Female rabbits were orally given taltirelin hydrate at a dose of 0 (control), 0.15, 1.5, or 15 mg/kg from day 6 to day 18 of gestation. Females were sacrificed on day 29 and their fetuses were examined. Neither death nor adverse effects on food consumption in dams were found in any dose groups. In the 15 mg/kg group, rapid breathing and decreased body weight gain in dams were temporally observed. No adverse effect of taltirelin hydrate on reproductive function was detected in any groups. In the fetal examination, taltirelin hydrate had no teratogenic, lethal, or growth retardation effects in any groups. These results show that the no-toxic dose levels of taltirelin hydrate are 1.5 mg/kg for general toxicity in dams, and 15 mg/kg for reproductive function of dams and for development of their offspring.

Four-, 13- and 52-week repeated dose toxicity studies of taltirelin tetrahydrate(TA-0910), a thyrotropin-releasing hormone(TRH) analogue, were carried out in rats. Through the three studies, TA-0910 solution was administered orally at doses of 3, 30 and 300 mg/kg/day. The animals receiving TA-0910 showed hyperlocomotion, grooming and wet dog shaking which were attributable to the central effects similar to those of TRH, but there was no death nor obvious deterioration of health caused by the treatment. Body weights decreased in males of 300 mg/kg group, and food consumption was on the upward trend in females in 300 mg/kg group. In 13- and 52-week studies, females receiving 300 mg/kg showed elongated estrous cycle, although it was not an evident change. Blood examinations revealed increases in erythrocyte count, hemoglobin and hematocrit in 300 mg/kg group. Reductions in serum(plasma) proteins and lipids, and drug-metabolizing enzyme activity of the liver were regarded as non-specific changes, as they were sporadic and slight in 300 mg/kg group. Salivary gland and adrenal weights increased in 300 mg/kg group. For the thyroid, weights increased in 300 mg/kg group in the 4- and 13-week studies, and increases of microfollicles and cell debris were observed microscopically in each treated group in the 52-week study. These changes seemed to be related with hormonal action of TA-0910, but the effects on animals were judged slight from plasma TSH and thyroid hormone levels after 4 weeks of dosing. The non-toxic dose was estimated to be 30 mg/kg/day, through the rat repeated dose toxicity studies. All the above changes were alleviated or abolished by 4-week recovery period.

Taltirelin tetrahydrate (TA-0910), novel thyrotropin-releasing hormone (TRH) analogue, was orally administered to dogs as dose levels 0.5, 5, and 50 mg/kg for 13 weeks and 0.15, 1.5 and 15 mg/kg for 52 weeks. Blood concentrations of test substance measured in 52-week study revealed that absorption of TA-0910 was with dose-dependent manner and not changed through the treatment period. These toxicokinetics suggested that there were no alterations on metabolism of TA-0910 with repeated treatment. The animals receiving 5 or 50 mg/kg showed decrease in body weight or suppression of body weight gain, and decrease in food intake (13-week study). As an abnormality in general conditions, vomiting and salivation (5 mg/kg or more, both in 13- and 52-week studies), increase in behavior as water intake (5 mg/kg or more, 13-week study), and hyperlocomotion (50 mg/kg) were observed. Elevating GPT values were noted temporally in the animals treated with 5 mg/kg or more (both in 13- and 52-week studies) without abnormal findings in histopathology. The thyroid weights were increased in treated animals receiving 5 or 50 mg/kg in 13-week study, but no histopathological changes were noted. Electron microscopy revealed dilatation of granular endoplasmic reticulums in follicular cells of thyroid from 50 mg/kg group in 13-week study. It was concluded that no-effect levels of 13- and 52-week studies were 0.5 mg/kg and 1.5 mg/kg, respectively.

The acute toxicity studies of taltirelin tetrahydrate (TA-0910), a new thyrotropin-releasing hormone (TRH) analogue, were performed in Slc:ddY mice, Slc:Wistar rats and beagle dogs of both sexes. The drug was administered to mice and rats by oral (p.o.), intravenous (i.v.) and subcutaneous (s.c.) routes, and to dogs by the p.o. and i.v. routes. LD50 values were more than 5,000 mg/kg in mice and rats of both sexes by the p.o. and s.c. routes. Some mice and rats died immediately after i.v. injection, the LD50 values were more than 2,000 mg/kg in mice of both sexes and calculated as 799 and 946 mg/kg in male and female rats, respectively. The minimum lethal doses were more than 2000 mg/kg in dogs of both sexes by the p.o. route. Though all dogs treated intravenously with 1000 mg/kg could survive during the observation period, a female dog with 500 mg/kg died on the day after administration. In general condition, hyperactivity, tremor and straub tail, that reflected central stimulatory effects of TA-0910, were observed in mice and rats, and also wet dog shaking in only rats. Vomiting and hyperactivity were seen in dogs by the p.o. route, and exaltation (during the dosing) and sedation by the i.v. route. In addition, salivation and transient tachycardia were observed in the both routes. In blood chemical examination, the transient changes of glucose, protein, lipid and/or serum enzyme were shown. In autopsy, no notable changes were seen in mice, rats and dogs.

The thyrotropin-releasing hormone (TRH) analog, RX 77368, (p-Glu-His-(3,3'-dimethyl)-Pro-NH2) injected intracisternally (i.c.) at low doses increases gastric mucosal blood flow through vagal cholinergic and calcitonin gene-related peptide dependent pathways. The influence of the mast cell stabilizer, ketotifen, on i.c. injection of RX 77368 (1.5 ng)-induced changes in gastric mucosal blood flow (hydrogen gas-clearance technique), gastric acid secretion and mean arterial pressure was studied in urethane-anesthetized rats. RX 77368 increased gastric blood flow by 131% and systemic arterial pressure by 11 mm Hg and decreased gastric mucosal vascular resistance by 54% whereas acid secretion was not altered within the 30 min period post injection. Ketotifen had no effect on these basal parameters but abolished i.c. RX 77368-induced increased gastric mucosal blood flow and decreased gastric vascular resistance. These data suggest that mast cells may be part of the peripheral mechanisms involved in vagal gastric hyperemia induced by TRH analog injected i.c. at a low dose.

In the present study, two ulcer models--central thyrotropin-releasing hormone (TRH) injection and cold-restraint stress (CRS) application--were compared. Animals were treated either with salmon calcitonin (sCT) or saline intracerebroventricularly (ICV) before CRS exposure or ICV TRH injection. In both models, besides ultrastructural properties, ulcer indexes and lipid peroxidation (LP) and glutathione (GSH) levels of liver and stomach were determined. While TRH treatment did not affect GSH and LP levels of the stomach and led to a slight decrease in hepatic GSH levels, CRS induced a marked reduction in gastric and hepatic GSH and an increase in LP levels of both tissues. sCT pretreatment prevented the reduction of gastric and hepatic GSH levels and morphological damage of both tissues in the CRS group. However, the same treatment did not prevent the TRH-induced reduction of hepatic GSH levels and, interestingly, it worsened the ultrastructural disturbances in the liver. Although sCT prevented macroscopic ulcer formation in both models, it did not totally reverse the microscopic effects of TRH.

Montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, was examined for mutagenicity in the reverse mutation test, the chromosome aberration test in vitro, and the micronucleus test in mice. The reverse mutation test was performed at dose range of 156.25-5,000 micrograms/plate using Salmonella typhimurium strains, TA1535, TA100, TA1537, and TA98, and Escherichia coli WP2uvrA. The drug did not increase revertant colonies significantly in any of the test strains with or without metabolic activation system (S-9mix). The chromosome aberration test was carried out at dose range of 300-4,800 micrograms/ml using cultured Chinese hamster lung cells (CHL/IU). No significant increases of the frequencies of cells with chromosomal aberrations were observed with or without metabolic activations. The micronucleus test was conducted in the bone marrow cells of Slc:ddY male mice. Mice were given the drug by a single intraperitoneal administration at doses of 0, 250, 500, 1,000, and 2,000 mg/kg. There were no significant increases in the frequencies of micronucleated polychromatic erythrocytes at any dose levels. These results show that montirelin hydrate has no mutagenic activity in vitro or in vivo.

A repeated dose toxicity study of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, was conducted in beagle dogs. Male and female dogs were given the drug intravenously for 26 weeks at doses of 0 (control), 0.02, 0.2, 2 and 20 mg/kg. After discontinuation of the treatment, a 9-week recovery test was also conducted. No deaths related to the treatment were observed. Nasal discharge in all dose groups, and tremor, salivation and emesis in the 0.2 mg/kg group and over were seen. Decrease in body weight gain was observed in the 2 and 20 mg/kg groups. There were no abnormalities in body temperature, and food and water consumptions. Urinalysis and electrocardiographic, ophthalmoscopic and hematologic examinations failed to show any abnormalities attributable to the treatment. In blood chemical examination, increase in T3 level was observed in the 2 and 20 mg/kg groups of females. There were no pathological findings attributable to the treatment. The changes mentioned above were satisfactorily reversible. The nasal discharge seen in the 0.02 mg/kg group was considered to be of no toxicological significance. These results show that the NOAEL of montirelin hydrate is 0.02 mg/kg for 26-week repeated dose toxicity in dogs.

A repeated dose toxicity study of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, was conducted in Sprague-Dawley rats. Male and female rats were given the drug intravenously for 5 weeks at doses of 0 (control), 0.05, 0.5, 5 and 50 mg/kg. After discontinuation of the treatment, a 4-week recovery test was also conducted in the 0, 0.5 and 50 mg/kg groups. No deaths related to the treatment were observed. Tremor was seen in the 50 mg/kg group. Polyuria was observed in the 5 and 50 mg/kg groups. There were decreases in body weight gain in the 0.5 mg/kg group and over of males, and in food consumption in all male dose groups and increase in water consumption in the 5 and 50 mg/kg groups. In blood chemical examination, decrease in triglyceride was observed in the 5 and 50 mg/kg groups of males. Urinalysis showed increase in urine volume in the 0.5 mg/kg group and over. Ophthalmoscopic and hematologic examinations failed to show any abnormalities attributable to the treatment. Pathological examination disclosed serous cell hypertrophy of the submandibular gland in all dose groups and increase in its organ weight in the 0.5 mg/kg group and over. The changes mentioned above were satisfactorily reversible except for the serous cell hypertrophy of the submandibular gland in the 50 mg/kg group. The decrease in food consumption and serous cell hypertrophy of the submandibular gland in the 0.05 mg/kg group were considered to be of no toxicological significance. These results show that the NOAEL of montirelin hydrate is 0.05 mg/kg for 5-week repeated dose toxicity in rats.

A study of the effect of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, during the period of organogenesis was conducted in New Zealand white rabbits. Female rabbits were given the drug intravenously at dose levels of 0 (control), 0.01, 0.1 and 1 mg/kg from day 6 to day 18 of pregnancy. Female rabbits were sacrificed on day 29 of pregnancy for examination of their fetuses. In the 0.1 mg/kg group, food consumption decreased slightly. In the 1 mg/kg group, tachypnea, salivation and rhinorrhea were observed, and body weight and food consumption decreased and water consumption increased. The drug had no effect on the number of corpora lutea and implantations, or on fetal mortality, on fetal body weights, on placental weight, on sex ratio, or on external, visceral and skeletal development of the fetuses. These results show that the NOAEL of montirelin hydrate are 0.1 mg/kg for general toxicity in mother animals, and 1 mg/kg for pregnancy of mother animals and for development of fetuses.

Montirelin hydrate (NS-3) is a new drug for the treatment of disturbance of consciousness. The single dose toxicity studies of its degradation product and impurity (CNK-603) and its metabolite (CNK-6004) were conducted in Slc: ddY mice. The compounds were administered intravenously to male and female mice. Deaths occurred in both sexes of mice receiving more than 125 mg/kg of CNK-603. There were no treatment-related effects on survival in both sexes of mice receiving doses up to 2,000 mg/kg of CNK-6004. Approximate lethal dose of CNK-603 was 125 mg/kg and lethal dose of CNK-6004 was more than 2,000 mg/kg. Decrease in locomotor activity was observed in mice receiving the two compounds. Tremor, prone position and dyspnea were seen in mice receiving CNK-603. The body weight showed no changes attributable to the dosing of the two compounds in mice. In autopsies, congestion and hemorrhage in the lung were observed in dead mice given CNK-603. There were no remarkable changes in mice given CNK-6004. These results show that the lethal dose of CNK-603 is over 4 times lower than that of montirelin hydrate, and that CNK-6004 is less toxic than montirelin hydrate.

A study of the effect of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, during the perinatal and lactation periods was conducted in Sprague-Dawley rats. Female rats were given the drug intravenously at dose levels of 0 (control), 0.02, 1 and 50 mg/kg from day 17 of pregnancy to day 21 after delivery. All pregnant rats were allowed to deliver naturally for postnatal examination of their offspring. In the 1 and 50 mg/kg groups, food and water consumptions decreased after delivery and the weights of adrenals of the dams increased. In addition, tremor, disappeared within some minutes, was observed during administration period in all dams given 50 mg/kg. Moreover, body weight gain was suppressed after delivery, and the weights of submaxillary glands increased, and the weights of thymus and liver decreased in the dams given 50 mg/kg. The drug did not affect delivery. The drug did not have any adverse effects on the newborn including the number of live newborns, birth index and body weights of live newborn. In the 1 or 50 mg/kg group, body weight gains were suppressed and food consumption decreased in the offspring. The drug did not have any adverse effects on the postnatal development of the offspring such as differentiation, functional development, emotionality, motor ability, learning ability or reproductive performance. These results show that the NOAEL of montirelin hydrate are 0.02 mg/kg for general toxicity in mother animals, 50 mg/kg for reproductive function in mother animals and 0.02 mg/kg for their offspring.

An antigenicity study of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, was conducted in Hartley guinea pigs. Animals were sensitized twice by subcutaneous injections of montirelin hydrate in combination with Freund's complete adjuvant and twice by intramuscular injections of montirelin hydrate alone. Montirelin hydrate was found to be negative in the homologous passive cutaneous anaphylaxis test carried out with sera from the sensitized guinea pigs. Negative results were also obtained in the active cutaneous anaphylaxis test and the active systemic anaphylaxis test in guinea pigs sensitized with montilerin hydrate. These results show that montirelin hydrate has no antigenicity under the present experimental conditions.

A repeated dose toxicity study of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, was conducted in beagle dogs. The dogs were given the drug intravenously for 4 weeks at doses of 0 (control), 0.0002, 0.002, 0.02, 0.2, 2 and 20 mg/kg in males and 0, 0.2, 2 and 20 mg/kg in females. After discontinuation of the treatment, a 4-week recovery test was also conducted in the 0 and 20 mg/kg groups. No deaths related to the treatment were observed. There were no changes in body weight gain, and food and water consumptions. Nasal discharge was seen in all dose groups. Salivation, emesis and hypoactivity were observed in the 0.2 mg/kg group and over. Licking chops were seen in the 2 and 20 mg/kg groups. Trembling and agitated/restless behavior were seen in the 20 mg/kg group. Electrocardiographic examination revealed elevated heart rate in the 0.2 mg/kg group and over. Ophthalmoscopic and hematologic examinations, and urinalysis failed to show any abnormalities attributable to the treatment. Blood chemical examination disclosed increases in T3 level in the 2 and 20 mg/kg groups of males and in T4 level in the 0.2 mg/kg group and over of males. There were no pathological findings attributable to the treatment. The changes mentioned above were satisfactorily reversible. The nasal discharge seen in the 0.02 mg/kg group and below was considered to be of no toxicological significance. These results show that the NOAEL of montirelin hydrate is 0.02 mg/kg for 4-week repeated dose toxicity in dogs.

A study of the effect of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, during the period of organogenesis was conducted in Sprague-Dawley rats. Female rats were given the drug intravenously at dose levels of 0 (control), 0.02, 1 and 50 mg/kg from day 7 to day 17 of pregnancy. Twenty-three or twenty-five female rats per dose level were sacrificed on day 20 of pregnancy for examination of their fetuses, and the pregnant rats (13-15 per dose levels) were allowed to deliver naturally for postnatal examination of their offspring. In the 1 or 50 mg/kg group, water consumption and the weights of adrenals of the dams increased and the weights of the thymus of the dams decreased. In addition, tremor, disappeared within some minutes, was observed from day 7 to day 16 of pregnancy in all dams given 50 mg/kg. Moreover, food consumption increased and the weights of the submaxillary glands of the dams given 50 mg/kg increased. The drug had no effect on the number of corpora lutea and implantations, on fetal mortality, on fetal body weights, on sex ratio, or on external, visceral and skeletal development of the fetuses. The drug also did not affect delivery. The drug did not have any adverse effects on the newborn such as the number of live newborns, birth index and body weights of live newborn, or on the postnatal development of the first generation offspring (F1) such as differentiation, functional development, emotionality, motor ability, learning ability or reproductive performance. The drug also had no adverse effects of the second generation offspring (F2). These results show that the NOAEL of montirelin hydrate are 0.02 mg/kg for general toxicity in mother animals, 50 mg/kg for pregnancy and delivery of mother animals and 50 mg/kg for development of their offspring.

A study of fertility and early embryonic development to implantation of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, was conducted in Sprague-Dawley rats. Male rats were given the drug intravenously from 63 days before mating to the end of mating period and female rats from 14 days before mating to day 7 of pregnancy; the dose levels for both males and females were 0 (control), 0.02, 1 and 50 mg/kg. The females were sacrificed on day 20 of pregnancy for examination of their fetuses. In the 50 mg/kg group, tremor, disappeared within some minutes, was observed during administration period in all animals. Food and water consumptions increased in the females and body weight gain was suppressed in the males. Moreover prolonged estrus cycle was observed at early period of the administration in the females, but it recovered at late period of the administration. However, there were no toxicities in the males and females in the 1 mg/kg or less groups. The drug had no adverse effects on reproductive function of the parent animals, or on development of fetuses. These results show that the NOAEL of montirelin hydrate are 1 mg/kg for general toxicity in parent animals, and 50 mg/kg for reproductive function of the parent animals and for development of fetuses.

A repeated dose toxicity study of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, was conducted in Sprague-Dawley rats. Male and female rats were given the drug intravenously for 26 weeks at doses of 0 (control), 0.0004, 0.02, 1 and 50 mg/kg. After discontinuation of the treatment, a 9-week recovery test was also conducted in the 0, 1 and 50 mg/kg groups. No deaths related to the treatment were observed. Tremor and polyuria were seen in the 50 mg/kg group. There were decrease in body weight gain, and increase in water consumption in the 1 and 50 mg/kg groups. In those dose groups of males, decrease in food consumption was observed. Ophthalmoscopic examination failed to show any abnormalities attributable to the treatment. Blood chemical examination disclosed decrease in total cholesterol in the 50 mg/kg group. There were also decreases in phospholipid in the 50 mg/kg group of females, and in triglyceride in the 1 and 50 mg/kg groups of males. Urinalysis and hematologic examination failed to show any abnormalities attributable to the treatment. In pathological examination, serous cell hypertrophy and increase in organ weight of the submandibular gland were observed in the 1 and 50 mg/kg groups, and increase in organ weight of thyroid was revealed in the 0.02 mg/kg group and over. The changes mentioned above were satisfactorily reversible except for the decrease in food consumption in the 50 mg/kg group of males. Increased thyroid weight in the 0.02 mg/kg group was considered to be of no toxicological significance. These results show that the NOAEL of montirelin hydrate is 0.02 mg/kg for 26-week repeated dose toxicity in rats.

A vascular irritability study of montirelin hydrate (NS-3) injection, a new drug for the treatment of disturbance of consciousness, was conducted in Japanese white rabbits. The concentration of montirelin hydrate was 4 mg/ml. Saline and 0.75% acetic acid were used as negative and positive control, respectively. In a part of the ear vein, 0.05 ml of each compound was allowed to remain for 3 min after intravenous injections once a day for 8 days. Inflammation in peri-venous region and thrombus were macroscopically observed in injection sites of rabbits with the montirelin hydrate injection group. However, no changes were seen with the negative control group. Histopathological examination revealed periphlebitis, desquamation of endothelial cells and thrombus in rabbits given montirelin hydrate injection or saline. But incidence and degree of periphlebitis caused by montirelin hydrate injection were higher than those caused by saline. On the other hand, the irritating changes caused by 0.75% acetic acid were severer than those by montirelin hydrate injection. These results show that montirelin hydrate injection has a very weak vascular irritability in the ear of rabbits.

The single dose toxicity studies of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, were conducted in Slc:ddY mice, Slc:SD rats, and beagle dogs of both sexes. The drug was administered intravenously (i.v.) to mice, rats and dogs, and intramuscularly (i.m.) to mice and rats. The animals were observed for 14 days after administration. LD50 values were more than 500 mg/kg and 200 mg/kg in mice and rats, respectively, by the i.v. route, and more than 20 mg/kg in both animal species by the i.m. route. In dogs, the minimum lethal dose was more than 200 mg/kg by the i.v. route. Mice that received more than 125 mg/kg by the i.v. route showed tremor and a decrease in locomotor activity during administration and for 30 min thereafter. Mice that received more than 5 mg/kg by the i.m. route showed tremor 5 min after administration and for 2 hr thereafter. Rats that received more than 50 mg/kg by the i.v. route showed tremor, and those that received 200 mg/kg by the same route showed a decrease in locomotor activity and ataxic gait, during and immediately after administration. Rats that received more than 5 mg/kg by the i.m. route showed tremor, and those that received 20 mg/kg by the same route showed salivation 5 min after administration and for 30 min thereafter. Dogs that received more than 12.5 mg/kg by the i.v. route revealed excitement, biting, vocalization, mydriasis, salivation, urination, defecation, licking chops, vomiting, increase in heart rate, panting, hyperthermia, tremor and conjunctival injection during administration and for 6 hr thereafter. The body weight, food consumption and water consumption, and pathological findings showed no changes attributable to the dosing of montirelin hydrate in any animal.

The influence of intracaudate administration of N-methyl-D-aspartic acid (NMDA) and of the competitive NMDA receptor antagonist, DL-2-amino-5-phosphonovaleric acid (AP-5) was studied on thyrotropin-releasing hormone (TRH)-induced scratching in rabbits. NMDA (28 nmol) significantly increased the latency of TRH-induced scratching but did not modify the duration of this behaviour. Conversely, AP-5 (0.5 mumol) significantly potentiated scratching duration. Since TRH-induced scratching has been reported to be a dopamine-dependent behaviour, these results suggest that NMDA receptor ligands modulate dopaminergic neurotransmission.

We have recently reported that basic fibroblast growth factor (bFGF) acts in the brain to inhibit the secretion of gastric acid and pepsin, two major aggressive factors in the pathogenesis of gastric ulcer formation. In the present study, we determined whether or not bFGF has an anti-ulcer action via the central nervous system, using male Wistar rats. The intracisternal injection of bFGF dose-dependently (0.1-1.0 microgram(s)/rat) inhibited the severity of gastric ulcers induced by water-immersion restraint stress or central thyrotropin-releasing hormone. The same doses of peripherally injected bFGF failed to protect the gastric mucosa from these ulcerogenic procedures. These results suggest for the first time that bFGF has a mucosal protective effect through a mechanism involving the central nervous system. It is speculated that this anti-ulcer action of bFGF is, at least in part, dependent upon its gastric antisecretory effect.

We have recently found that interleukin-1 (IL-1) acts in the central nervous system to potently inhibit gastric acid and pepsin secretion in rats. In the present study, we examined the effects of IL-1 on the development of gastric mucosal lesions induced by intracisternal (i.c.) thyrotropin-releasing hormone (TRH), a neuropeptide known to centrally stimulate gastric secretion. Pretreatment with i.c. injected IL-1 (10 ng/rat) significantly suppressed the severity of TRH-induced gastric erosions. On the other hand, the same dose of i.c. injected IL-1 failed to exert a cytoprotective action for the gastric mucosa against orally administered absolute ethanol. These results suggest that IL-1 has an anti-ulcer effect mainly through its inhibitory action on gastric secretion.

The behavioral effects of the TRH analogue RX77368, dimethyl proline-TRH (3, 10 and 30 mg/kg IP), in 5-, 10- and 20-day-old rat pups were investigated. The peptide induced shaking behavior and increased locomotion as early as 5 days after birth. At 20 days RX77368 also produced rearing, stereotyped mounting and grooming (mainly licking and chewing of the forepaws). Additionally, RX77368 produced hypothermia and antinociception in the infant rats. These responses, which were generally, although not always, comparable with those found in adults, agree with biochemical studies showing high levels of TRH receptors in the brain and spinal cord in the first three weeks following birth.

Bilateral intra-amygdalar (i/am) microinjections of TRH (1 and 10 micrograms) and physostigmine (10 micrograms) into the central nucleus (CEA) aggravated cold restraint stress (3 hr at 4 degrees C) induced gastric ulcer formation in rats, whereas atropine (1, 5 and 10 micrograms) attenuated this phenomenon. Similar stress ulcer reducing effects were seen with chlordiazepoxide (CDP, 10 mg/kg, IP) and midazolam (1, 3 and 10 micrograms, i/am). Pretreatment of rats with atropine or CDP antagonized the ulcerogenic effects of both TRH and physostigmine. Further, when administered intra-CEA, midazolam neutralized the effects of TRH in a dose-related manner. These results are discussed in light of TRH-acetylcholine-benzodiazepine/GABA interactions within the amygdaloid complex during stress ulcer formation.

Like dibutyryl cyclic AMP, thyrotropin releasing factor (TRF) has potent antianesthetic properties, but only dibutyryl cyclic AMP shortens narcosis dose-relatedly. In contrast, only TRF reverses amobarbital-induced hypothermia (dose-relatedly). In naive rats, dibutyryl cyclic AMP (25-200 mug) induces convulsions while TRF (5-100 mug) produces intermittent hyperactivity and sedation but never convulsions. To determine whether behavioral events may be regulated in the central nervous system through an interaction of the two naturally occurring compounds, TRF (5-100 mug) and dibutyryl cyclic AMP (25-200 mug) were injected simultaneously into the lateral ventricle of the brain of naive rats or rats anesthetized with amobarbital (80 mg/kg). TRF (12.5-50 mug) and dibutyryl cyclic AMP (100-200 MUG) DID NOT SHORTEN NARCOSIS FURTHER THAN DIBUTYRYL CYCLIC AMP alone. Amobarbital protected against the lethal effects of the two compounds injected simultaneously. Long-lasting locomotor disorders and mortality rate increased with increasing doses of TRF (12.5-25 mug) and dibutyryl cyclic AMP (100-200 MUG) GIVEN TO NAIVE RATS. Results did not support the postulate that cyclic AMP is the second messenger of TRF.

Plasma levels of exogenous TRH were measured in eleven normal subjects. They were assessed as to their possible associations with the TRH disappearance rate in vivo, with the TSH and prolactin response, and with the behavioral (and side) effects of TRH. Max. levels of plasma TRH occurred consistently two minutes after injection of TRH (0.5 mg). They ranged from 8.1 to 75.1 ng/ml and were negatively correlated with the in vivo TRH disappearance rate. The latter, in turn, was positively correlated with such factors as height and body surface. Max. plasma TRH levels were not related to the magnitude of the TSH or prolactin response, or to the occurrence of behavioral effects. Nor were they related to the TRH-induced side effects although these effects occurred during the time of increasing TRH plasma levels.

The mechanisms underlying the thermal effects induced by intrahypothalamic administration of either d-amphetamine or thyrotropin-releasing hormone (TRH) has been investigated in conscious rats. Direct administration of d-amphetamine (1-10 micrograms in 1 microliter) or TRH (1-4 micrograms in 1 microliter) into the preoptic anterior hypothalamus caused hyperthermia or fever at the ambient temperature (Ta: 8, 22 and 30 degrees C) studied. The fever induced by d-amphetamine or TRH was due to increased metabolic heat production at Ta 8 degrees C, while at Ta 30 degrees C the fever was due to cutaneous vasoconstriction in the rat. At Ta 22 degrees C, the fever was due to both increased metabolism and cutaneous vasoconstriction. Furthermore, the fever induced by intrahypothalamic administration of TRH was greatly reduced by pretreatment with intrahypothalamic administration of either yohimbine (a blocking agent of alpha-adrenergic receptors), phentolamine (a blocking agent of alpha-adrenergic receptors) or DL-propranolol (a blocking agent of beta-adrenergic receptors) in the rat. However, the fever induced by d-amphetamine was antagonized by pretreatment with yohimbine or phentolamine, but not with DL-propranolol in the rat. These observations indicate that the adrenergic receptor mechanisms within the hypothalamus are involved in the fever induced by both d-amphetamine and TRH.

As a preliminary step in evaluating the use of thyrotropin releasing hormone (TRH) linked to toxin fragments for systemic treatment of pituitary disease, we have examined the metabolic degradation, tissue distribution, renal excretion, and toxicity in rats of TRH-CRM45 which consists of TRH coupled to CRM45, a diphtheria toxin-related polypeptide. For comparison, we have similarly studied CRM45, CRM26 (a smaller diphtheria toxin-related fragment), and ricin A. All four proteins were found to concentrate in the kidney and liver relative to blood (in comparison to bovine serum albumin), tissue:plasma ratios for the kidney being much higher than those observed for the liver. Radioiodinated CRM45 and ricin A were rapidly cleared from the circulation with similar patterns. Systemic toxicity studies showed that at doses greater than 2 micrograms/100 g body wt (bw), CRM45 caused a decrease in growth rate and caused renal damage. CRM45 modified with 2-pyridyldithio(propionate) groups as well as TRH-CRM45 was significantly less toxic than CRM45, as was TRH-CRM45. CRM26 had no discernible effect on the growth rate of the animals. Ricin A, at a dose of 50 micrograms/100 g bw slowed the growth rate of rats, but specific liver or kidney damage could not be detected. These findings define an upper range of doses for possible therapeutic use.

Although a pressor effect of 500 micrograms i.v. thyrotropin-releasing hormone (TRH) in noncardiac patients has been reported, the effect of a lesser dose of TRH (200 micrograms) in cardiac patients has not been evaluated. We performed a 200 micrograms i.v. TRH test to exclude thyrotoxicosis in 20 cardiac patients, aged 38 to 42 years. No clinical side effects were noted, but increments in systolic and diastolic blood pressure of 21.8 +/- 2.7 and 17.3 +/- 1.6 mm Hg (SE), respectively, were documented. Mean arterial pressure rose from 104.9 +/- 2.9 to 123.7 +/- 5.5 mm Hg (SE) after TRH (P less than 0.001). In nine patients the pressor response persisted for 5 to 20 min, and blood pressures of 220 mm Hg systolic and 145 mm Hg diastolic were recorded. We conclude that the 200 micrograms TRH i.v. has a significant pressor effect.

The N3im-methyl analogue of thyrotropin release hormone (methyl-TRH) was compared with TRH as a thyrotropin releaser in 30 euthyroid volunteers (ages 19-61 years). The mean TSH response to 100 mug of methyl-TRH was greater (P less than 0.005) than the TSH response to 500 mug of TRH from 10 min to 240 min after giving the releasing factors. The mean peak TSH (at 30 min), maximum deltaTSH, and integrated TSH response area were greater (P less than 0.005) after administration of methyl-TRH than after TRH. The TSH response to methyl-TRH was significantly greater (P less than 0.05) for the 11 females than for the 19 males in this study. The mean baseline TSH was correlated with the maximum deltaTSH (r = 0.72, P less than 0.01) after methyl-TRH stimulation. The mean serum T3 concentration after methyl-TRH was significantly elevated at 60 min, peaked at 210 min and remained significantly elevated at 240 min. The peak serum T3, maximum T3 and T3 response area were significantly greater (P less than 0.005) after giving methyl-TRH than after TRH. The methyl-TRH induced T3 response area was 1.4 times the TRH induced T3 response area. The serum T4 concentration after methyl-TRH was elevated at 90 min (P less than 0.005), reached a peak at 210 min, and at 240 min was still 1.25 times the mean baseline T4. The peak serum T4, maximum deltaT4 and T4 response area after methyl-TRH were significantly greater than after TRH. The methyl-TRH induced T4 response area was 1.4 times the TRH induced T4 response area. The data indicate that methyl-TRH is a more potent thyrotropin releaser than TRH. Since N3im-methyl-histidine has been found in the brain, the possibility that this methyl analogue of TRH is a physiologic thyrotropin releaser should be evaluated.

The previously reported, dose-related, and selective neurotoxic action of 100 to 200 nmol quinolinic acid on intrastriatal injection was confirmed. A slight neurotoxicity was obtained with 250 nmol thyroid releasing hormone but not with a similar dose of L-pyroglutamic acid.