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The behavioral effects of carbon monoxide (CO) administered via IP injection were investigated in the mouse. Mice were trained to lever press under a fixed-ratio (FR) 100 schedule of water reinforcement. Thirty-min test sessions were conducted either immediately or 30 min following IP injections of air (100 ml/kg) or CO (7.5, 15, 30, 50 or 100 ml/kg). CO produced a decrease in rates of responding which was exhibited earlier and lasted longer with increasing doses. Motor performance was also measured with the inverted-screen test following the same doses of CO at either 5, 15, 30, 60, 120 min or 24 hr post-injection. Performance was affected in a dose-and time-dependent fashion. Peak carboxyhemoglobin (COHb) levels were observed at 15 or 30 min and were 20%, 32%, 42%, 51% and 60% for 7.5, 15, 30, 50 and 100 ml/kg CO, respectively. COHb saturation alone was not always a good predictor of behavioral effects since both level and duration of exposure contributed to behavioral impairment. The results also show that the IP route can be used to study the toxicity of CO.

Reaction of cyclohexadienylium-Fe(CO) 3 complexes (7) and (8) with sodiomalono-nitrile gives the carbo-spirocyclic derivatives (9) and (10), whilst reaction with benzylamine and removal of iron leads to the azaspirocyclic enones (15) and (16), respectively.

The total synthesis of the C-18 oxygenated aspidosperma alkaloid (±)-limaspermine (3) is described using tricarbonyl{-1–4-η-[1-methoxy1-4-(3-methoxycarbonylpropyl)cyclohexa-1,3-diene}iron (15) as a readily available ring C precursor. A formal synthesis of (±)-aspidospermine (1) from 4-ethylanisole, via the organoiron derivative (23) is also described as a model study for an alternative route to the C-18 functionalised alkaloids.

The effects of carbon monoxide (3.75, 7.5, 15 and 30 ml/kg, IP) alone and in combination with ethanol (1.1 g/kg), nicotine (1.1 mg/kg), caffeine (36.1 mg/kg), chlorpromazine (2.2 mg/kg), diazepam (10 mg/kg), pentobarbital (23.1 mg/kg), d-amphetamine (1.4 mg/kg) or morphine (13.3 mg/kg) were evaluated in mice. Animals were trained to lever press under a fixed-ratio 32 schedule of water reinforcement. Response rates following CO-drug combinations were compared with the expected additive effects determined by the sum of the effects of each agent administered alone. CO (15 and 30 ml/kg) in combination with ethanol produced supra-additive effects. CO-chlorpromazine and CO-d-amphetamine combinations often produced greater than additive response-rate suppression, although differences from additivity did not reach statistical significance. The effects on response rates following CO in combination with nicotine, caffeine, diazepam, pentobarbital, or morphine were additive. These results suggest that concurrent use of therapeutic or abused drugs and CO exposure may place an individual at higher risk for behavioral toxicity.

Toluene shares pharmacological properties with other abused central nervous system depressants such as ethanol and the barbiturates. Although tolerance has been clearly demonstrated for these classic CNS depressants, evidence of tolerance following repeated toluene exposure is equivocal. The present work examined if tolerance would develop to the effects of repeated toluene exposure on learned behavior and examined the possibility that external discriminative stimuli could influence these effects. Two variants of a fixed-consecutive-number schedule of reinforcement were used as components in a multiple schedule. The components differed in whether or not behavior within them was under the control of external discriminative stimuli. Rats were exposed daily for two hours to toluene (1780 to 4500 ppm). Different patterns of effects emerged from repeated exposure; some rats displayed tolerance while the performance of others deteriorated. Behavior controlled by external discriminative stimuli was more resistant to disruption and showed tolerance more readily than did behavior not under such control.

Toxicokinetic experiments with toluene that rely on data pooled from several animals have typically provided estimates of rate constants based on single exponential functions; in the present study a within-subject design was used to describe the time course of toluene in the blood to see if additional exponential terms could be resolved. Each rat was exposed for 2 h to either 1 000, 1 780, or 3 000 ppm of toluene. Blood samples were drawn at different times from indwelling jugular cannulae, and blood toluene concentrations were determined by vapor phase equilibrium chromatography. There was substantial variability between the peak blood values of the animals at each exposure concentration. Nonlinear regression was used to determine regression parameters for data drawn from individual animals. A bi-exponential function was found to minimize significantly the residual sum of squares observed during elimination. However, only a single exponential function could be resolved reliably during uptake. The mean half-time during uptake was approximately 34 min; the two half-times for elimination averaged approximately 6 and 90 min. Because of between-subject variability, a more accurate description of the time course of toluene uptake and elimination can be provided by kinetic studies that use a within-subject design.

External discriminative stimuli can modify the behavioral effects of d-amphetamine. Previous work with the pigeon has demonstrated that some aspects of performance on the fixed consecutive number schedule are changed less if a discriminative stimulus indicates when reinforcement is available. This effect has now been replicated with the rat using both simple and multiple schedules. Moderate doses of d-amphetamine (0.56--1.0 mg/kg) usually produced large decreases in reinforced runs when no external cue indicated the possibility of reinforcement. Adding discriminative stimuli when the number requirement was met decreased the drug effect. As was true in the pigeon, response rate measures did not differ between the two stimulus control conditions. Thus, external stimulus control diminishes the drug effect in both species, despite the fact that key pecking was studied in the pigeon and lever pressing in the rat. Evidence was also seen of a possible increase in discriminative stimulus control by d-amphetamine.

The abuse of volatile solvents may be due to their ability to produce an intoxication similar to that produced by classical central nervous system depressants such as the barbiturates and ethanol. To evaluate this hypothesis, mice were trained to discriminate pentobarbital from saline injections in a two-lever operant task. Stimulus generalization was examined following 20-min inhalation exposures to toluene (300-5400 ppm). In 8 of 10 subjects, pentobarbital-lever responding occurred following toluene exposure indicating an overlap in the discriminative stimulus properties of toluene and pentobarbital.

It has been found that a considerable degree of regiochemical control may be achieved during addition of stable enolate nucleophiles to tricarbonyl(cyclohexadienyl)iron complexes of general structure I by changing the enolate countercation. The results indicate an interplay between steric, coulombic and frontier orbital controlling factors during the bond-forming reaction.

A method of constructing the quaternary carbon, corresponding to C-20 of Aspidosperma alkaloids, via tricarbonylcyclohexadienyliumiron salts is described.

The present work investigates the contribution of various second messenger systems to Ca2+-induced phosphatidylserine (PS) exposure in red blood cells (RBCs) from sickle cell disease (SCD) patients. The Ca2+ dependence of PS exposure was confirmed using the Ca2+ ionophore bromo-A23187 to clamp intracellular Ca2+ over 4 orders of magnitude in high or low potassium-containing (HK or LK) saline. The percentage of RBCs showing PS exposure was significantly increased in LK over HK saline. This effect was reduced by the Gardos channel inhibitors, clotrimazole and charybdotoxin. Nevertheless, although Ca2+ loading in the presence of an outwardly directed electrochemical gradient for K+ stimulated PS exposure, substantial exposure still occurred in HK saline. Under the conditions used inhibitors of other second messenger systems (ABT491, quinacrine, acetylsalicylic acid, 3,4-dichloroisocoumarin, GW4869 and zVAD-fmk) did not inhibit the relationship between [Ca2+] and PS exposure. Inhibitors of phospholipase A2, cyclooxygenase, platelet-activating factor, sphingomyelinase and caspases, therefore, were without effect on Ca 2+-induced PS exposure in RBCs, incubated in either HK or LK saline.

We are grateful to V. Chen, D. Higgs, A. Hill, J. Guerrerio, J. Old, N. Neary, J. Roux, A. Sofro, B. Sykes, D. Tumen, and R. Ward, for access to DNA samples, and to the Wellcome Trust, for support.

The novel trans-bicyclic-perhydro-2(1H)-quinoxalinones 4, 6 and 7 and the tricyclic-perhydropyrrolo[1,2-a]-quinoxalin-4(5H)-one derivatives 8 and 9 are prepared via a ring opening and spontaneous ring closing reaction of the aziridines 2 and 3 with the α-amino acids glycine, L-alanine, L-proline and L-phenylalanine. This methodology was used to prepare 5 and 10 which are novel rigid analogues of the kappa opioid compound 1. Treatment of aziridine 3 with methyl carbamate gave the cyclic urea 11.

This paper describes the synthesis, structure-activity relationships (SAR) of mu and kappa opioid binding affinities, and analgesic properties of a series of novel highly selective kappa opioid N-[(2-aminocyclohexyl)aryl]acetamide and N-[(2-aminocyclohexyl)aryloxy] acetamide derivatives. Ten compounds, 14, 15, 31-37, and 39 (Tables I and II), show a marked kappa selectivity of greater than 100:1 over mu binding, with high affinity for the kappa opioid receptor (approximately 10(-8) - 10(-9) M). Compound 39, (S,S-trans)-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-4-benzo[b] furanacetamide hydrobromide, has the highest mu/kappa selectivity, 780:1 (kappa Ki = 4.2 nM), reported to date. Four of these compounds, 14, 15, and their S,S-trans enantiomers, 37 and 39, respectively, produce effective analgesia by oral administration, as assayed by a rat-paw pressure test (RPP) (MPE50 = 24, 26, 8.3, and 12 mg/kg, respectively). The R,R-trans isomer, 38, was inactive in binding and RPP. The analgesic effect was reversed by administration of naloxone, confirming these effects are opioid in character. Optimal activity is produced when the basic nitrogen atom is in a pyrrolidine ring, the aryl group is a 10-pi-electron-rich aromatic system, such as 4-benzo[b]thiophene, 4-benzo[b]furan, or 4-chlorophenoxy, and overall lipophilicity lies within the range log P = 3.5-5.0.

The behavioral effects of d-amphetamine have been shown to be modulated by stimulus control, with less impairment of performance occurring when control is great. When the fixed-consecutive-number schedule is used (on which at least a specified consecutive number of responses must be made on one operandum before a single response on another will produce a reinforcer), response rate tends to be invariant but reinforcement frequency is not. This study asks whether the differences in reinforcement frequency that usually accompany changes in stimulus control could themselves be responsible for the performance differences. Two versions of the fixed-consecutive-number schedule of reinforcement were combined into a multiple schedule within which stimulus control was varied but differences in reinforcement frequency were minimized by omitting some reinforcer deliveries during the component that usually had the higher reinforcement frequency. In one component, a compound discriminative stimulus was added with the eighth consecutive response on the first lever; a single response on the second lever was then reinforced. In the other component, no such stimulus was presented. With no added stimulus, large decreases occurred in the number of runs satisfying the minimum requirement for reinforcement at doses of drug that produced only minimal changes when an added stimulus controlled behavior. Thus, increased stimulus control diminishes the behavioral changes produced by d-amphetamine even when the possible contribution by baseline reinforcement rate is minimized.

Little is known about the nature of the acute intoxication produced by exposure to high concentrations of toluene such as that which occurs with spills and in solvent abusers. The intoxication may be similar to that produced by classic central nervous system depressants such as the barbiturates. To investigate this hypothesis, drug discrimination procedures were used to compare the acute effects produced by toluene and pentobarbital (PB). Mice were trained to discriminate toluene (100 mg/kg, ip) from vehicle in a two-lever task in which responding was under the control of a fixed-ratio 20 (FR20) schedule of food presentation. Generalization tests were conducted after 20-min inhalation exposures to toluene (150–3600 ppm) and 20 min after injections with either PB (5–30 mg/kg) or morphine (3–20 mg/kg). Most mice generalized to inhaled toluene and to PB in a concentration- or dose-related fashion, but not to morphine. These results show that the effects of injected toluene can be established as a discriminative stimulus in mice, and that these stimulus effects are independent of route of administration. Shared discriminative stimulus properties with PB suggest that toluene produces an acute intoxication like that of other classic CNS depressants.

This paper describes the chemical synthesis and the development of structure-activity relationships (SAR) for the kappa opioid receptor affinity and mu/kappa opioid receptor selectivity of novel N-[(2-aminocyclohexyl)aryl]acetamide derivatives. The SAR of this series are investigated by consideration of structural modifications made to the aromatic moiety, the amide linkage, and cyclohexane and the pyrrolidine ring substituents of the prototype kappa selective agonist, PD117302 (trans-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzo[b]thiophene-4- acetamide) (1). The kappa and mu opioid receptor binding affinities of 23 novel compounds are reported. It is observed that optimal mu/kappa receptor selectivity is obtained with a benzo[b]thiophene aromatic system attached via the C-4 position, which is discussed in terms of steric and electronic parameters. The amide linkage has been replaced with the reversed amide, an ester, an aminomethylene, a thioamide, and a secondary amide. The best of these isosteres is the N-methyl amide. Substitution of the pyrrolidine ring of PD117302 in the 3-position with a hydroxymethylene group increases the mu/kappa selectivity compared to the unsubstituted compound, e.g. compound 14, trans-(+/-)-N-methyl-N-[2-[3-(hydroxymethyl)-1-pyrrolidinyl] cyclohexyl]-4-benzo[b]furanacetamide monohydrochloride, mu/kappa receptor selectivity = 244. The cis fused, 4,5 dimethyl ether substituted cyclohexane analogue trans-(+/-)-N-methyl-N-[4,5-dimethoxy-2-(1-pyrrolidinyl) cyclohexyl]-benzo[b]thiophene-4-acetamide monohydrochloride (32) has high in vitro kappa opioid receptor affinity (Ki = 16 nM) and equipotent analgesic activity to morphine after iv administration in rats.

An improved synthesis of the (±)-limaspermine intermediate (3b), starting from tricarbonyl-1—4-η-[4-isopropoxy-1-(2-methoxyethyl)cyclohexa-1,3-diene]iron (2c), is described.

A study of the regioselectivity of enolate nucleophile addition to tricarbonyl(dienylium)iron complexes with structure (1) is reported. It has been found that better selectivity for the 1-substituted dienylium terminus is achieved using 4-isopropoxy-substituents than with 4-methoxy-substituents. The nature of the enolate countercation is also found to affect significantly the regioselectivity of its addition, and these results are discussed in terms of the factors which are likely to control the reaction.

The synthesis of tricarbonyl(cyclohexadienylium)iron salts containing tosyloxy-substituents in the lateral chain, and their reactions with nucleophiles to give spirocyclic compounds, is described. The synthesis and spiroannelation reactions of complexes with gem-dinitrile and cyanoester groups in the lateral chain are presented.