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The presence of serotonin-containing neurons in the hypothalamus of the rat and cat was studied by immunohistochemistry. In the rat, a group of serotonin-immunoreactive neurons was observed in the nucleus dorsomedialis hypothalami following nialamide pretreatment at a high dosage (over 300 mg/kg). In the cat, serotonin-immunoreactive neurons were sparsely distributed in the ventral part of the middle to the caudal lateral hypothalamic area after high dosage (500 mg/kg) nialamide pretreatment.

The magnetic properties of Y2Fe14-xCoxB (0 ⩽ x ⩽ 12) and Y2Fe14-xMnxB (0 ⩽ x ⩽ 5) have been investigated by 57Fe Mossbauer spectroscopy. Single crystalline samples of Y2Fe14-xCoxB were used in magnetization measurements. The magnetic hyperfine field of Fe in Y2(Fe, Co)14B decreases monotonically with increasing Co content, and the value obtained are not entirely coincident with those estimated from the magnetization. The results are discussed in connection with the rigid band model and the magneto-volume effect. Mn substitution considerably reduced both of the magnetization and the Curie temperature. It was found that the Mn atom has no magnetic moment and take no part in magnetic interaction.

Exogenous horseradish peroxidase (HRP, Type VI, Sigma) was applied as a marker for retrograde neuroanatomical tracing in the nigroneostriatal system and the sciatic nerve of adult rats. The retrograde transport and intraneuronal fate of HRP was examined with light and electron microscopy.In the nigroneostriatal system, the labeled neurons containing many brown granules in their perikarya were observed in the ipsilateral substantia nigra 3-4 hours after an injection of HRP, confirming the existence of a nigroneo-striatal pathway. Ultrastructually, these granules appear as multivesicular and lysosomal bodies in the perinuclear region.The labeled nerve cells of the spinal ganglia were also observed within 12 hours after the application of HRP in the sciatic nerve. The HRP positive brown granules had accumulated in the perinuclear region and were rapidly degraded by the lysosomal system disappearing 2 weeks after the injection.In instances of long periods of survival, characteristic lysosomal bodies which included crystals, crystalloid and laminar structures were found.

With a view to improving the immunohistochemical technique for the demonstration of bioactive substances, i.e., neuropeptides and biogenic amines in the mammalian central nervous system, the procedures of immunoperoxidase methods were examined and some modifications for obtaining consistent results were developed.Brains of pharmacologically untreated animals were utilized as the material of the present study. The time through thoracotomy and preperfusion was reduced as much as possible. Perfusion fixation was performed at an increased rate, using a blood pump (hemolizer). The first fixative was a mixture of 4% formaldehyde, 0.2% picric acid, and 0.5% glutaraldehyde in phosphate buffer; the second was 4% formaldehyde and 0.2% picric acid in phosphate buffer acidified to pH6.5 with acetic acid; and the third was buffered formaldehyde solution. The osmotic pressure of all these fixatives was 1550-1650mOsM. Sections 25μm thick were produced on a Microslicer, followed by application of the freezing-thawing technique. The free-floating sections were incubated in a low concentration of antibody solution diluted by 0.5% Triton X-100 in phosphate buffer for a longer period than usual, under cool condition. The reactive substances resulting from the avidinbiotin-peroxidase complex method were enhanced by osmication. With these methods, the serotonin and GRH neurons could be clearly and finely visualized.

The spinal cord of the rat in the different developing stages was light and electron microscopically investigated by a modified ZIO impregnation technique. As the animal matured, both the myelin sheath and synaptic vesicles in nerve endings increased their affinity to ZIO impregnation. However, ZIO reactivity of the glial cells, on the contrary, was reduced with the maturation. This method appears to be useful and convenient for the demonstration of myelinated axons without further staining and for the detection of some kind of the glial cells in the early developing stage.

A quantitative and immunoelectronmicroscopical analysis of serotonin nerve fibers in the primary visual cortex of the monkey (Macaca fuscata) was made using a sensitive immunoperoxidase method for serotonin. The overall numerical density of serotonin-containing varicosities in the primate striate cortex was approximately 770,000/mm3 and the highest concentration of immunoreactive varicosities (ca. 1,400,000/mm3) was observed in the upper portion of layer IVc, the next highest concentration being in layer IVb (ca. 1,180,000/mm3). At the ultrastructural level, the electron dense immunoreactive products were observed in the small granules (10-65 nm in diameter). The varicosities were usually small (0.5-1.0 micron in diameter) and made contact with both stellate and pyramidal cells. Serotonin fibers were often in close apposition to the poorly myelinated axons in layers IVb, V, and VI, and they rarely formed distinct synaptic structures with unlabelled neuronal elements.

The distribution of vasoactive intestinal polypeptide (VIP), gastrin-releasing peptide (GRP)/bombesin, somatostatin, vasopressin, neuropeptide Y (NPY) and serotonin was examined immunohistochemically in the suprachiasmatic nucleus (SCN) of male rats genetically deficient for vasopressin (Brattleboro strain). VIP-containing neurons and their varicose fibers were preferentially distributed in large numbers in the ventromedial part of the SCN. GRP/bombesin-containing neurons and their fibers were also gathered in the ventral part of the SCN, particularly in the ventromedical region of the nucleus. Somatostatin-containing neurons and their fibers were prominent in the rostral and middle portions of the SCN, where the highest concentration of immunoreactivity was restricted in their ventromedial part. No vasopressin-immunoreactivity was found at all throughout the SCN. Profuse NPY-containing varicose fibers were observed in the ventrolateral part of the SCN, but no immunoreactive neurons were distributed in this nuclear region. Serotonergic fibers showed a topographic arrangement in the SCN: a serotonin-immunoreactive nerve plexus was predominantly distributed in the ventrolateral part. These findings indicate that the SCN of Brattleboro rats is composed of distinct subdivisions of immunoreactive cell bodies and fibers. The distribution of the five peptides and indoleamine within the SCN in the Brattleboro strain was compared with that in normal Long-Evans rats. Furthermore, both strains of rats were exogeneously administered with arginine-vasopressin, but no conspicuous difference in the regional patterns of immunoreactivity was detected. The possible role of vasopressin in the SCN is discussed.

Using a peroxidase-antiperoxidase immunohistochemical method, the distribution of serotonin nerve fibers was studied in the neocortex of the monkey (Macaca fuscata). All layers of the neocortex showed evidence of serotonin fibers, both fine and thick. Unlike the distribution in rodents, different patterns of distribution were noted in each neocortex of the primate. Among the cortical areas — area 4, 3-1-2, 17, 18, 41 and 42 — the primary visual cortex (area 17) contained the highest density of immunoreactive fibers, while the primary motor cortex (area 4) possessed the lowest concentration. The most outstanding finding was a dense and laminar distribution of serotonin fibers in area 17, particularly within the upper portion of layer IVc. In area 3-1-2, 18, 41 and 42, a fairly uniform density of immunoreactive fibers was observed across the six cortical layers, apart from a relatively dense plexus of fine serotonin fibers in layer IV.

Es wurden die von H. KNOCHE beschriebenen Nodulus-Fasern im Hypophysentrichter des Hundes untersucht. Die Nodulus-Fasern, die in ihrem Verlauf hier und da eigentumliche, rundliche kleine knotchenformige, nichtgomoriphile Verdickungen zeigen, werden in der inneren und auseren Zone der Infundibulumwand durch die BIELSCHOWSKY-GROSsche Silverimpragnationsmethode dargestellt. Sie sind in der auseren Zone besonders reichlich vorhanden und haben ein typisches Aussehen. Sie zeigen eine innige Beziehung mit den Hypophysenpfortadergefasen, indem sie in Form des Terminalretikulums an den Endothelzellen der sog. Spezialgefasen endigen. Es scheint wahrscheinlich, das die beiden Arten der Nervenfasern, d. h. die neurosekretorischen gomoriphilen und die nodularen argyrophilen Fasern, eine wichtige Rolle in der funktionellen hypothalamoadenohypophysaren Verbindung spielen.Die Nodulus-Fasern reihen sich in der auseren Zone der Infundibulumwand nebeneinander, indem sie zur auseren Flache des Trichters vertikal stehen, und endigen meist an der adenoneurohypophysaren Kontaktflache, aber eine Anzahl derselben dringt weiter den Blutgefasen entlang in das Drusengewebe des Lobus tuberalis ein.

Es wurde die von GREVING benannte "Inselbildung" im Hypophysentrichter von versehiedenen Saugetieren untersucht. Das Bild der Inselbildung entsteht durch das auserordentlich reichliche, perivaskulare Gitterfasergewebe, welches den Raum zwischen einem zentral verlaufenden Gefas und den gomoriphilen, hypothalamoneurohypophysaren Nervenfasern ausfullt. Die Ependymfasern und die absteigende neurosekretorische Bahn umgehen das Gitterfaserretikulum bogenformig. Nach der vollkommenen Darstellung des Gitterfasergewebes erscheint eine Insel nicht mehr als eine helle, ungefarbte Sphare, sondern sie tritt umgekehrt als eine dunkel gefarbte Sphare auf. In der Insel sind einige Adventitia- und Neurogliazellen, und ein sehr feines, nicht gomoriphiles Nervenfasergeflecht bemerkbar. Die Adventitia- und Neurogliazellen zeigen haufig eine konzentrisch kreisformige Anordnung. Das Gitterfasergewebe scheint auch hier als eine extravaskulare Saftbahn (von Prof. T. KIHARA) fur das Neurosekret zu dienen.Es wurde nach den Methoden von WEED experimentell festgestellt, das diese Saftbahn mit dem subarachnoidalen Raum in ununterbrochener Verbindung stehen kann.

Es wurde die histologische Bedeutung des Sulcus tuberoinfundibularis (SPATZ, DIEPEN und GAUPP 1948) aufgezahlt und der Beweis fur die Richtigkeit der Anschauung, das diese Furche oder Linie als die Grenze zwischen dem Tuber cinereum und dem Infundibulum hypophyseos, also die Grenze zwischen dem Hypothalamus und der Hypophysis zu betrachten ist, wurde geliefert.

Wir untersuchten uber den intravaskularen Eintritt des hypothalamischen Neurosekrets in unverandert granularer bzw. kolloidaler Form bei verschiedenen Saugetieren, Vogeln und Amphibien. Wir bemerkten bei Hund intravaskular eingetretene, mit HEIDENHAINs Eisenhamatoxylin gefarbten Neurosekretgranula im Kapillarnetz des Nucleus paravent-ricularis und bei Hund, Schwein und Leopard mit der GOMORIschen Methode gefarbte Granula im proximalen Kapillargeflecht der Hypophysenpfortader und bei Hund, Katze, Leopard, Kaninchen, Huhn, Ente und Frosch solche in den Hinterlappengefasen. In allen diesen Fallen war die Sekretmasse auch perivaskular vorhanden. Wir haben aber keinen Anhaltspunkt, den intravaskularen Eintritt des Neurosekrets in granular bzw. kolloidal bleibendem Zustand als ganz physiologisch anzuerkennen.

Es wurde beim Hunde eine neue, bis jetzt nicht beobachtete neurosekretorische tuberohypophysare Bahn beobachtet und beschrieben. Ihre Ursprungszellen liegen zerstreut subependymal an dem unteren Teil der lateralen Wand des dritten Ventrikels, rostral von dem Gewebe des Mamillarkorpers, grostenteils im Gebiete des Nucleus infundibularis tuberis von H. SPATZscher Schule. Diese Ursprungszellen sind kleinzellig, gomoriphil und aldehydfuchsinophil. Ihre Fortsatze sind meistens bipolar oder pseudounipolar und deutlich mehr gomoriphil als der Zelleib. Sie steigen vertikal ab, biegen fast rechtwinklig nach rostral und treten in die innere Schicht der hinteren Wand des Hypophysentrichters ein. Sie mischen sich im Trichter mit den durch Pars retroinfundibularis tuberis in den Hypophysengebiet eindringenden Fasern des Tractus paraventriculohypophyseus und werden von den letzteren nicht mehr unter-scheidbar. Es bleibt daher unklar, ob diese Bahn im Hypophysenstiel endigt oder im Hypophysenkorper. Aber es ist zweifellos, das eine neurosekretorische Bahn zwischen Tuber cinereum und Hypophysengebiet vorhanden ist. Dieser Befund wurde in 10 Fallen ausnahmslos bestatigt. In diesem neurosekretorischen System zeigen sich nicht nur Neuriten, sondern auch ihre Kollateralen und Dendriten gomoriphile Substanz. Das weitere Schicksal dieser gomoriphilen Substanz ist unklar. (Eine Arbeit uber dasselbe Thema wurde auch in Okajimas Folia anatomica japonica, Bd. 27, 1955 berichtet.)

Die Gestalt, die Sekretgranula und die Neurofibrillen der Nervenzellen des Nucleus supraopticus und des Nucleus paraventricularis wurden untersucht. Durch die HEIDENHAINsche Eisenhamatoxylinmethode werden die durch die GOMORIsche Methode unbemerkbaren, auserhalb der Zelleiber ausgetretenen Sekretgranula beobachtet. Sie scheinen dort direkt in die deutlich engmaschigen Kapillarnetze einzudringen. Die gomoriphilen Neuriten des Nucleus supraopticus gehen uber die Pars praeinfundibularis tuberis zum Infundibulum, wahrend diejenigen des Nucleus paraventricularis uber die Pars para- und retroinfundibularis tuberis. Die gomoriphilen Sekretgranula sind auch in den Wurzelteilen der Dendrniten sichtbar.

The argyrophilic cells in the lobus intermedius of dog and cat were studied.1. This argyrophilic cell and its processes are impregnated with silver especially well by YANO's borax-formalin method for neuroglia and by RIO HORTEGA's silver carbonate method.2. This cell can not be stained by GOMORI's CH-P method, GROS-SCHULTZE's method and BODIAN's method for nerve fiber. The cell has no NISSL substance. It can not be silvered by BIELSCHOWSKY-MARESCH-SANO's method for lattice fiber.3. These argyrophilic cells have their perikaryons at various levels in the lobus intermedius and extend bipolar or multipolar processes which end in cone-like enlargements on the wall of the hypophysial cavity and in the connective tissue between intermediate and posterior lobes. Some processes go further into the lobus posterior.4. The argyrophilic cell is neither a connective tissue element nor a nerve cell. There is not enough proof to decide that the cell is a neuroglia cell or that it is what ROMEIS called‘undifferenzierte Zellen’. Nothing is known about its origin, its nature and its relations with the neurosecretory system, but it may be supposed to be a cell participating in the mutual functional relations between intermediate and the posterior lobes.

Wir untersuchten histologisch den Eintritt des gomoriphilen hypothalamischen Neurosekrets in den dritten Ventrikel und stellten die folgende Befunde fest.1. Bei Saugetieren (Hund, Katze, Kaninchen und Leopard) und Vogeln (Haushuhn und Hausente) treten die gomoriphilen Substanzen, von der neurosekretorischen Bahn aus in die Trichterhohle des dritten Ventrikels ein.2. Bei der Krote treten sie von dem Gebiet des Nucleus pracopticus direkt in den dritten Ventrikel ein.

Die quantitativen Beziehungen zwischen der Zellgrose und der NISSL- und der GOMORI-Subsianz wurden in den hypothalamischen neuro-sekretorischen Kerne des Hundes untersucht. Die NISSL-Substanz ist in den kleineren Zellen schollenformig und im Verhaltnis zu der Zellgrose reichlicher vorhanden. Je groser die Zelle ist, umso mehr zerstreut sie sich staubformig. In den mittelgrosen Zellen ist die NISSL-Substanz staubformig in der Zellmitte und schollenformig in der auseren Zone. Umgekehrt ist die GOMORI-Substanz in den kleineren Zellen geringer und in den groseren reichlicher.

In dem Infundibulum und dem Hinterlappen der Hypophyse des Hundes werden bisweilen (etwa in 10%) gomoriphile Nervenzellen gefunden. In ihren histologischen Befunde stimmen sie vollig mit den Nervenzellen des Nucleus supraopticus uberein. In einem Fall wurde im Hinterlappen eine Gruppe von Zellen beobachtet, in welcher man alle mogliche Ubergange von normalen Nervenzellen bis zu den HERRINGkorpern findet. Aus diesem Befund kann man annehmen, das ein Teil der Nervenzellen in den neurosekretorischen Kernen im Hypothalamus holokrin sezerniert und die so degenerierten Zellen sich in Neurosekret, also in den HERRINGkorpern verwandeln, welch letztere in den Hinterlappen wandern. Nach der Auffassung der Verfasser sind die HERRINGkorper von verschiedener Herkunft. Sie sind z. B. durch Sekretstagnation bedingte Nervenfaserauftreibungen, in Sekret verwandelte Reste der Nervenzellen selbst oder durch andere Ursachen entstandene.

In der vorliegenden Untersuchung hat der Verfasser eine neue Verbesserung der BIELSCHOWSKY-MARESCHschen Methode fur die Silberimpragnation von Gitterfaser unternommen. Die Kernpunkte der Modifikation, die nach der Nachprufung und durch mannigfaltige Kombinationen der bisher bekannten Methoden gewonnen wurden, sind der Gebrauch des Eisenalauns als Sensibilisator und die Herstellung der ammoniakalischen Silberlosung nach der Rio Hortegaschen Tanninsilbermethode. Die Vorzuge dieser Methode sind ihr konstanter Erfolg, die Verkurzung der erforderlichen Zeit, und vor allem, die Unabhangigkeit des Resultates von der Arten der Fixierungs- und Einbettungsmittel.

We reported a modified reducing procedure of the BIELSCHOWSKY-GROS' method and made up a new method in which an additional after-staining of the silver-impregnated section by aldehyde-fuchsin is rendered possible.

Die Gefasverteilung, die VIRCHOW-ROBINschen Raume, die gliose Grenzmembran und die Ependymfasern in den Gebieten des Nucleus supraopticus und des Nucleus paraventricularis des Hundes wurden unter-sucht. Die sehr reichlich ausgebildeten Gefase dieser Kerngebiete sind alle von den aus Gitterfasernetzen gebildeten VIRCHOW-ROBINschen Gewebslucken umgegeben. Sie haben keine Verbindung mit denjenigen des Trichters und des Trichterstiels. Die Membrana limitans gliae superficialis wird immer dunner nach dem Sulcus tuberoinfundibularis, von wo sie distalwarts vollig verschwindet. Im Gebiete des Nucleus supraopticus und der Wand der Trichterhohle befinden sich sehr reichliche, vertikal zur Hirnoberflache verlaufende Ependymfasern, und eine Anzahl von ihnen endet mit dem Endfuschen an der Pia mater.

Mi esploris la uzeblecon de nova enlitiga substanco “Carbowax” precipe en la studado de nerva celajo, kaj povis konfirmi ke gi estas ankau por tin ci objekto laudinde anstatauiebla al parafina, celoidina kaj frostiga metodoj.

The hypothalamic oxytocin and vasopressin neurons of the monkey, Macaca fuscata, were demonstrated in Golgi-like images by a modified immunoperoxidase method. The magnocellular oxytocin and vasopressin neurons were distributed mainly in the supraoptic and paraventricular nuclei. In addition to these main nucleic, both types of magnocellular neurons were found in the accessory supraoptic nucleus, the periventricular and perifornical areas, the nucleus of the stria terminalis, the lateral hypothalamic area, and the pars interna of the globus pallidus. Magnocellular oxytocin neurons were seen immediately ventral to the anterior commissure, and parvocellular vasopressin neurons were localized in the medial portion of the suprachiasmatic nucleus. The preferential distribution of the oxytocin and vasopressin neurons was recognized not only in the supraoptic and paraventricular nuclei, but also in other areas. In all areas observed, the cytological difference between the oxytocin and vasopressin neurons could be identified. The area, of the perikarya of the vasopressin neurons was determined to be larger than that of the oxytocin neurons. Most of the axons of the oxytocin neurons issued from the perikarya, while the axons of the vasopressin neurons originated in most cases from the thick proximal dendrites. These results show that the oxytocin and vasopressin neurons are distributed in areas much broader than has hitherto been assumed, and that these two peptidergic neurons can be definitely differentiated morphologically as well as functionally.

Distribution of serotonin fibers in the spinal cord of the dog was investigated by means of a modified PAP method; a rabbit anti-serotonin serum prepared in the laboratory of the authors was used in this study. Serotonin fibers were revealed as PAP-positive dark-brown elements displaying dot-like varicosities (0.5--2.0 micrometers in diameter). In the spinal cord of the dog, the distribution of serotonin fibers is extensive. These fibers occur more densely in more caudal segments and are most prominent at the sacrococcygeal level. From the level of the cervical spinal cord to the upper lumbar region, the descending serotonin fibers are located immediately under the pia mater in the ventrolateral portion of the lateral funiculus. In more caudal segments, serotonin fibers are dispersed throughout the ventral and lateral funiculi. These longitudinal en passage-fibers send numerous transverse collaterals to the gray matter. Serotonin fibers are distributed abundantly in the laminae I and III of the posterior column, while only a few fibers are found in the lamina II (substantia gelatinosa). In the intermediate zone, two descending serotonin pathways, i.e., lateral and medial longitudinal bundles, are observed to coincide topographically with the nucleus intermediolateralis at C8(T1)--L3(L4) and the nucleus intermediomedialis at C1--Co respectively. The former is particularly prominent and communicates with the contralateral bundle via commissural bundles at intervals of 300--500 micrometers. The large motoneurons in the anterior column, especially those in the nucleus myorabdoticus lateralis within the cervical and lumbar enlargements, are closely surrounded by fine networks of serotonin fibers and terminals.

Immunoperoxidase histochemical investigations on pig hypophysis show that CRF immunoreactive nerve terminals are distributed around the blood vessels in the posterior lobe, particularly in its proximal part adjacent to the intermediate lobe. CRF immunoreactive nerve fibers are also seen in the intermediate lobe. The distribution of the CRF-containing nerve in the posterior lobe was found to be similar to that of the vasopressin-containing nerve terminals. The functional significance of the presence of CRF-containing nerve fibers representing a new component of the hypothalamo-hypophyseal neurosecretory system is discussed.

The ciliary body of the cat was investigated by fluorescence histochemistry and electron microscopy in an attempt to clarify its sympathetic innervation. Subconjunctival doses of 5-hydroxydopamine (5-OHDA) or 6-hydroxydopamine (6-OHDA) were given to establish the precise location of the sympathetic nerve terminals. The distribution of noradrenergic fibers and terminals was shown by fluorescence histochemistry to be sparse in the trabecular meshwork and the anterior portion of the ciliary muscle, but dense in the subepithelial tissue. The small and large dense core vesicles which occur in many nerve endings of the subepithelial tissue adjacent to the pigmented epithelial layer increased in electron density following the administration of 5-OHDA. Many degenerating nerve endings were found in the same region of animals treated with 6-OHDA. In contrast, there were few noradrenergic terminals in the ciliary muscle except for a portion of the smooth muscle which was shown to be dually innervated. The noradrenergic fibers in the subepithelial region and the trabecular meshwork may play an important role in aqueous secretion and outflow.

Distribution of serotonin-immunoreactive nerve fibers (5-HT fibers) in the subthalamic nucleus (STN) of the rat, cat and monkey was examined with a modified peroxidase-anti-peroxidase method using 5-HT antiserum without pretreatment. Fine varicose 5-HT fibers formed a fine network in the STN. Overall density of 5-HT fibers in the STN was highest in the monkey, and lowest in the rat. In the rat and cat, these fibers were distributed almost diffusely in the STN, whereas in the monkey they were particularly abundant in the ventral and medial parts of the STN. Many thick 5-HT fibers ran through the monkey STN.

The concept of a neurosecretory system consisting of a secretory center (production of bioactive substances in neuronal soma), a transport pathway (transport by axonal flow) and a neurohemal organ (storage and release at nerve endings) has been established through a series of histological studies on the hypothalamic magnocellular nuclei by two pioneers, Scharrer and Bargmann, together with their co-workers. In the early stages of the investigation, these actively secreting neurons were considered as exceptional neurons, separated from ordinary ones. However, since the application of modern techniques, such as electron microscopy, immunohistochemistry, and in situ hybridization, have made progress in tracing the cytological course from the gene expression to the release of bioactive product, it has become obvious that the classical definition of neurosecretion must be extended to include a variety of neuroepithelial derivatives, such as aminergic and peptidergic neurons and also paraneurons. At present, all neurotransmitters and neuro-modulators can be regarded as secretory substances produced in neurons. Newly developed precise techniques, e.g., a tracing method with a computer graphic system for the demonstration of axonal arborizations, have led to a dramatic change in our understanding of the fine details of cytological features, offering much more complicated structures than images presented by the classical impregnation technique. Immunohistochemically demonstrated serotoninergic neurons in the brain have revealed enormous reticular extensions and anastomoses of beaded processes which were previously unknown. Neurons composing the nervous system show greatly varied shapes and structures.(ABSTRACT TRUNCATED AT 250 WORDS)

A peroxidase-antiperoxidase immunohistochemical method with serotonin antiserum was employed to investigate the influence of reserpine on serotonin neurons of rats which were sacrificed at various times after injection (10 mg/kg i.p.). The disappearance of serotonin immunoreactivity induced by reserpine was detected only in the perikarya after 15 min, and then rapidly proceeded to the terminals. Between 2 and 4 h, immunoreactivity completely disappeared throughout the brain. The immunoreactivity reappeared in the perikarya after 6 h, and progressed toward the terminals gradually. However, there was an obvious difference in the rate of recovery of immunoreactivity between areas. After 7 days, the immunoreactivity returned to control levels.

The distribution of neuropeptide Y (NPY) immunoreactivity in the suprachiasmatic nucleus (SCN) and the lateral geniculate nucleus (LGN) of 5 kinds of mammals was studied using the peroxidase-anti-peroxidase method. In the SCN of the rat, hamster, chipmunk and cat, NPY-immunoreactive fibers were detected, particularly in the ventral part. In the 3 rodents and the cat, the somata and fibers of NPY-immunoreactive neurons were observed in the LGN. However, immunoreactive structures were not found in the SCN or LGN of the monkey. These results indicate that NPY immunoreactivity in the monkey LGN-SCN tract is absent.