Sex differences among oxytocin-immunoreactive neuronal systems in the mouse hypothalamus

Serial frontal sections of male and female mouse hypothalamus were immunostained with an antiserum to oxytocin, in order to study the topographical distribution of oxytocinergic perikarya and processes. Numbers of immunostained perikarya were counted in various hypothalamic regions. The oxytocin content of microdissected hypothalamic tissue samples was measured in radioimmunoassays. While the overall topographical distribution of oxytocin neurons in the classical magnocellular nuclei was similar in both genders, quantitative differences could be observed. The numbers of immunostained perikarya and the amounts of oxytocin found in females exceeded by far the numbers and amounts found in males. Male mice had fewer oxytocin-immunostained axons, projecting within the brain, than females. This was especially apparent in parts of the limbic system. Oxytocin-immunostained neurons in the perifornical region, the lateral hypothalamus and the ventral ansa lenticularis were mostly absent in males. It is possible that the observed sex differences in oxytocin immunoreactive brain architecture are due to the different hormonal conditions in males and females.     

Co-expression of vasopressin and androgen-binding protein in the rat hypothalamus

In previous studies we have observed the expression of androgen binding protein (ABP) in the rat hypothalamo-neurohypophysial system. With immunocytochemical double staining we found partial co-localization with oxytocin. In the present study we used antibodies to the anti-diuretic hormone arginine vasopressin (AVP) for co-localization with ABP in the rat hypothalamus. Both antigens were seen in the magnocellular paraventricular and supraoptic nuclei. Dense fiber networks with varicosities containing both AVP and ABP immunoreactivity were visible throughout the hypothalamus, the median eminence and in the posterior pituitary lobe. Double immunostaining revealed also co-existence in the parvocellular portion of the paraventricular nucleus and in the suprachiasmatic nucleus. ABP immunoreactive neurons in the preoptic region were devoid of AVP staining, AVP neurons in the bed nucleus of the stria terminalis stained only occasionally for ABP. We conclude that both the magnocellular and the parvocellular hypothalamic vasopressin systems are capable of expressing the steroid binding globulin, which is probably subject to axonal transport, along with the peptide hormone. Intrahypothalamic expression of ABP may be among the mechanisms necessary for rapid actions of steroids on hypothalamic neuroendocrine systems.     

The neurophysin-containing innervation of the forebrain of the mouse

The oxytocinergic and vasopressinergic innervation of the forebrain of normal mice was studied immunocytochemically by use of a set of mouse monoclonal anti-neurophysins applied to serial vibratome sections. The extensive hypothalamic and extra-hypothalamic location of these neuropeptides was revealed, with, or without colchicine pretreatment. Magnocellular perikarya immunoreactive for either oxytocin-neurophysin or vasopressin-neurophysin were concentrated mainly: in the anterior commissural nucleus; in various subdivisions of the paraventricular nucleus; in a profuse array in the periventricular region; in the supraoptic nucleus including its retrochiasmatic division; in various accessory nuclei; and as a number of cells scattered throughout the preoptic and hypothalamic regions. Extensive groups of parvocellular neurons, containing only vasopressin-neurophysin, were located in the suprachiasmatic nucleus including a ventromedial division, in the bed nucleus of the stria terminalis, and in the medial amygdaloid nucleus. Perikarya in the magnocellular nuclei were of generally similar size distribution and there was no evidence that distinct populations of magnocellular and parvicellular neurons, separable on the basis of size, had been labelled within these nuclei. Within the paraventricular nucleus, however, neurons in the posterior part were smaller than those located more anteriorly, and the cells containing oxytocin-neurophysin were slightly smaller than those containing vasopressin-neurophysin. Within the generally similar size distribution, magnocellular neurons of the anterior commissural nucleus were the largest. During processing, shrinkage of the tissue and immunolabeled cells had occurred. The immunocytochemical procedure delineated neuronal processes, in particular dendrites, very effectively. The dendrites were shown to project for far greater distances than is generally recognized, some were of a characteristic corkscrew-like morphology, and most were oriented in a well-defined pattern. Many dendrites of paraventricular neurons passed medially than caudally towards and then along the third ventricle. Most dendrites of supraoptic neurons, in particular those containing vasopressin-neurophysin, had an extensive anteroposterior course beneath the pia of the base of the brain. The axons containing oxytocin- and vasopressin-neurophysin were shown to take rather different paths from the paraventricular nucleus towards the median eminence.(ABSTRACT TRUNCATED AT 400 WORDS)     

Presence of estrogen receptor immunoreactivity in the oxytocin-containing magnocellular neurons projecting to the neurohypophysis in the guinea-pig.

The immunoperoxidase technique was used on adjacent sections of guinea-pig brain to compare precisely the distribution of estrogen receptor-immunoreactive cells and progesterone receptor-immunoreactive cells in the supraoptic nucleus and the paraventricular nucleus. Only estrogen receptor-immunoreactive neurons were found in the supraoptic nucleus. A large number of estrogen receptor-positive cells were observed in the periventricular magnocellular groups throughout the rostrocaudal extent of the paraventricular nucleus, whereas only a few progesterone receptor-immunoreactive cells were scattered in the anterior portion of this region. We used a combination of axonal tracing with double immunocytochemical detection to determine whether estradiol acts directly on the oxytocin-immunoreactive neurons which project to the neurohypophysis. Oxytocin-immunoreactive cells were found in the supraoptic nucleus, ventrally to the optic pathways, in subchiasmatic and retrochiasmatic areas, and in the anterior hypothalamic area. These cells were also retrogradely labeled by Granular Blue when this tracer was injected intravenously. In the paraventricular nucleus, the Granular Blue/oxytocin-positive cells were observed in the periventricular magnocellular groups whereas Granular Blue labeled neurons were found in both parvocellular and magnocellular components. We found that almost all the oxytocin-immunoreactive cells revealed estrogen receptor immunoreactivity. In conclusion, the comparative study of distribution of estrogen receptors and progesterone receptors in the guinea-pig supraoptic and paraventricular nuclei indicates that, in the supraoptic nucleus, only estrogen receptors are present and that, in the paraventricular nucleus, they are far more numerous than progesterone receptors. The present findings demonstrate that the magnocellular cells which contain estrogen receptors are oxytocinergic. In addition, these cells are retrogradely labeled pointing to a neurohypophysial projection. It is likely that estradiol controls the hypothalamo-neurohypophysial oxytocin system by direct action on the magnocellular neurons.     

Neuronal fields containing luteinizing hormone releasing hormone (LHRH) in mouse brain.

Immunocytochemical localization of the hypothalamic neurohormone luteinizing hormone releasing hormone (LHRH) was performed in mouse brain using the unlabeled peroxidase anti-peroxidase technique. Antisera derived from serum albumin conjugates to the decapeptide (or its analog) achieved by four conjugation procedures were used to determine the antigenic form of LHRH which reveals the various neuronal compartments. Antisera derived from LHRH conjugated to bovine serum albumin at the 2-histidyl position revealed a population of LHRH-containing cell bodies in the retrochiasmatic area, tuberal area and arcuate nucleus (the LHRH Field I). LHRH-positive fibers and terminals were seen in the organum vasculosum of the lamina terminalis and the median eminence. Fibers from the Field I neurons also coursed rostrally through the medial division of the hypothalamus and circumscribed the anterior commissure or projected dorsally into the thalamus. Antisera generated against conjugates to the N- or C-terminal of LHRH revealed a second population of LHRH perikarya. These were scattered throughout the medial preoptic, preoptic periventricular and medial septal areas (the LHRH Field II). A few neurons were found in the lateral arcuate nucleus. Fibers from septal and preoptic Field II neurons projected to the organum vasculosum. Immunoreactive fibers were found in the median eminence and thalamic regions in patterns similar to those previously described. Median eminence fibers appeared to arise in the regions of Field I neurons which did not stain with the end conjugate antisera. Antisera generated against a LHRH tyrosyl conjugate stained median eminence and organum vasculosum fibers but failed to stain perikarya in either field.The results of this study suggest the presence of two distinct immunoreactive populations of LHRH-containing perikarya, which are not contained within or restricted to any of the recognized hypothalamic nuclei.     

Plasticity of the interface between oxytocin neurons and the vasculature in late pregnant rats: an ultrastructural morphometric study.

Increased numbers of oxytocin-immunoreactive perivascular neurons have been shown to occur in the preoptic region and lateral hypothalamus of female rats around parturition. In the present study, electronmicroscopical immunocytochemistry and morphometry were used to examine such perivascular oxytocinergic neurons as well as those in the classical magnocellular nuclei in late pregnant and lactating rats. In 22 d pregnant animals and in rats killed after 2 d of lactation, numerous oxytocinergic neurons were found in direct apposition to the outer basement membrane of arterioles, venules, and capillaries. The distance between immunoreactive neurons and blood vessels was significantly lower in these animals than in 9 d lactating rats and in ovariectomized controls. It is likely that, around parturition, oxytocinergic perivascular neurons are uncovered by active retraction of glial elements. This plasticity is perhaps facilitated by changing hormonal conditions around parturition. The observed changes seem to be transitory and might reflect altered secretory properties of perivascular oxytocinergic neurons.     

Estrogen receptor α is involved in the estrogenic regulation of arginine vasopressin immunoreactivity in the supraoptic and paraventricular nuclei of ovariectomized rats

The ovarian hormone estradiol regulates the expression of arginine vasopressin gene and the release of arginine vasopressin by magnocellular hypothalamic neurons. Magnocellular neurons express estrogen receptor β and are contacted by afferent neurons that express estrogen receptor α. In this study we have assessed the effect of selective ligands for estrogen receptors to determine the subtype of estrogen receptor involved in the regulation of arginine vasopressin immunoreactivity in the supraoptic and paraventricular nuclei of ovariectomized rats. The volume fraction occupied by arginine vasopressin immunoreactive material was significantly increased in both nuclei in the animals treated with estradiol compared to the animals injected with vehicle. A similar result was obtained with an estrogen receptor α selective agonist. In contrast, the administration of an estrogen receptor β selective agonist did not significantly affect arginine vasopressin immunoreactivity. This finding suggests that estradiol may regulate arginine vasopressin levels on the supraoptic and paraventricular nuclei by acting on afferent neurons expressing estrogen receptor α.     

Immunohistochemical identification of the oxytocin and vasopressin neurons in the hypothalamus of the monkey (Macaca fuscata)

Summary 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.Supported by grants (No. 56440022, 56770037) from the Ministry of Education, Science, and Culture, Japan     

A study of subcortical afferents to the hippocampal formation in the rat.

The distribution of neurons in diencephalon and brainstem which project upon the hippocampal formation has been analyzed in adult rats by the injection of horseradish peroxidase into different parts of the hippocampus and dentate gyrus and the related retrohippocampal structures, including the subicular complex and the entorhinal cortex. Any large injection of horseradish peroxidase inlo the hippocampal region results in the retrograde labeling of some neurons in each of the following structures: in the thalamus—the nucleus reuniens, the parataenial and paraventricular nuclei, the anterodorsal and antermedial nuclei, and the laterodorsal and lateral posterior nuclei; in the hypothalamus, septum and preoptic region—the medial septal nucleus and the diagonal band of Broca, the substantia innominata, the lateral preoptic area, the magnocellular preoptic nucleus, and the anterior amygdaloid area, the dorsomedial hypothalamic nucleus, the lateral and posterior hypothalamic areas, the ventral premammillary nucleus, the supramammillary region, and parts of the tuberomammillary and lateral and medial mammillary nuclei: in the brainstem: the ventral tegmental area, the substantia nigra, the interpeduncular and interfascicular nuclei, the dorsal and median nuclei of the raphe, the dorsal and laterodorsal tegmental nuclei, the locus coeruleus, the central gray, and certain of the tegmental reticular fields.It is clear that these afferents to the hippocampal formation do not comprise a single, homogeneous system, and that their terminations within the hippocampal region are not restricted to a particular topographic level (i.e. septal, intermediate or temporal).     

Atrial natriuretic polypeptide: topographical distribution in the rat brain by radioimmunoassay and immunohistochemistry

The widespread distribution of neurons containing alpha-atrial natriuretic polypeptide-like immunoreactivity in the rat brain was demonstrated using radioimmunoassay and immunohistochemistry in conjunction with specific antisera. The highest concentrations of alpha-atrial natriuretic polypeptide-like immunoreactivity were in the hypothalamus and septum, with low but still appreciable concentrations in the mesencephalon, cerebral cortex, olfactory bulb and thalamus by radioimmunoassay. Immunohistochemical studies clearly showed that the perikarya of immunoreactive neurons are most prevalent in the ventral part of the lateral septal nucleus, periventricular preoptic nucleus, bed nucleus of the stria terminalis, periventricular and dorsal parts of the paraventricular hypothalamic nucleus, ventromedial nucleus, dorsomedial nucleus, arcuate nucleus, median mamillary nucleus, supramamillary nucleus, zona incerta, medial habenular nucleus and the periaqueductal grey matter. Scattered neurons were seen in the cingulate cortex, endopiriform nucleus, lateral hypothalamic area, and pretectal and dorsal thalamic areas. In addition to the areas mentioned above, high concentrations of immunoreactive varicose fibers were seen in the glomerular layer of the olfactory bulb, external layer of the median eminence, central to paramedian parts of the interpeduncular nucleus and the paraventricular hypothalamic nucleus. The globus pallidus, medial and central amygdaloid nuclei, dorsal raphe, dorsal parabrachial nucleus, locus coeruleus, vagal dorsal motor nucleus, solitary nucleus and some circumventricular organs, including the subfornical organ and organum vasculosum laminae terminalis, contained considerable numbers of immunoreactive varicose fibers. In dehydrated rats and homozygous Brattleboro rats, the pattern of alpha-atrial natriuretic polypeptide-immunoreactive neurons and varicose fibers was qualitatively similar to that seen in normal conditioned rats. This study gives an atlas of the distribution of the alpha-atrial natriuretic polypeptide-containing neuronal system in the rat brain and provides the groundwork for studying the influence of this new peptide on various brain functions.     

New data on the immunocytochemical localization of thyrotropin-releasing hormone in the rat central nervous system

An antiserum raised against the synthetic tripeptide pyroglutamyl-histidyl-proline (free acid) was used to localize thyrotropin-releasing hormone (TRH) in the rat central nervous system (CNS) by immunocytochemistry. The distribution of TRH-immunoreactive structures was similar to that reported earlier; i.e., most of the TRH-containing perikarya were located in the parvicellular part of the hypothalamic paraventricular nucleus, the suprachiasmatic portion of the preoptic nucleus, the dorsomedial nucleus, the lateral basal hypothalamus, and the raphe nuclei. Several new locations for TRH-immunoreactive neurons were also observed, including the glomerular layer of the olfactory bulb, the anterior olfactory nuclei, the diagonal band of Broca, the septal nuclei, the sexually dimorphic nucleus of the preoptic area, the reticular thalamic nucleus, the lateral reticular nucleus of the medulla oblongata, and the central gray matter of the mesencephalon. Immunoreactive fibers were seen in the median eminence, the organum vasculosum of the lamina terminalis, the lateral septal nucleus, the medial habenula, the dorsal and ventral parabrachial nuclei, the nucleus of the solitary tract, around the motor nuclei of the cranial nerves, the dorsal vagal complex, and in the reticular formation of the brainstem. In the spinal cord, no immunoreactive perikarya were observed. Immunoreactive processes were present in the lateral funiculus of the white matter and in laminae V-X in the gray matter. Dense terminal-like structures were seen around spinal motor neurons. The distribution of TRH-immunoreactive structures in the CNS suggests that TRH functions both as a neuroendocrine regulator in the hypothalamus and as a neurotransmitter or neuromodulator throughout the CNS.     

Immunocytochemical study of Met-enkephalin-like cell bodies in the cat hypothalamus

The distribution of methionine-enkephalin-like cell bodies in the hypothalamus of the cat was studied using an indirect immunoperoxidase technique. Previously, intraventricular or intratissular injections of colchicine were carried out. Met-enkephalin-like neurons were located in all hypothalamic nuclei. The densest clusters of immunoreactive perikarya were observed in the nucleus arcuatus, median eminence, regio praeoptica and perifornical region, whereas the nucleus supraopticus and hypothalamus anterior had the lowest density. In other hypothalamic nuclei the density of methionine-enkephalin (Met-enkephalin) cell bodies was intermediate.     

Lateral septum-medial hypothalamic connections: An electrophysiological study in the rat

Participation of both the lateral septum and the medial hypothalamus in similar behavioral and homeostatic functions, combined with anatomical data indicating a modest descending lateral septum projection to medial hypothalamic areas, prompted an investigation of the electrophysiology of lateral septum—medial hypothalamic connections in pentobarbital-anesthetized male Sprague-Dawley rats. Field potentials evoked by lateral septum stimulation were prominent within the hypothalamic ventromedial nucleus; their distribution closely overlapped with amygdala-evoked field potentials. Lateral septum stimulation evoked orthodromic responses from 67% of 800 medial hypothalamic and preoptic neurons (55.5% excitatory, latency 17.5 ± 0.5 ms; 11.5% inhibitory, latency 19.1 ± 1.4 ms), including 15 of 31 tuberoinfundibular neurons activated antidromically from the median eminence. 37.4% of cells responded orthodromically to both lateral septum and amygdala stimulation, whereas only 5.8% of cells demonstrated orthodromic responses to both lateral septum and midbrain periaqueductal gray stimulation.These observations suggest that lateral septum neurons influence the excitability of many medial preoptic and hypothalamic neurons, and indicate a convergence of lateral septum and amygdala influences onto 37% of medial hypothalamic cells. In the rat, the lateral septum's influence on adenohypophyseal hormone secretion appears to be mediated indirectly, i.e. through monosynaptic connections with medial hypothalamic tuberoinfundibular neurons.     

Oxytocin-containing pathway to the bed nuclei of the stria terminalis of the lactating rat brain: immunocytochemical and in vitro electrophysiological evidence.

Immunocytochemical staining within the forebrain of lactating rats revealed oxytocin-immunoreactive perikarya in a continuum running from the anterior parvocellular hypothalamic paraventricular nucleus through the anterior commissural nucleus and perifornical region. Beaded axons could be seen arising from these perikarya to enter the bed nuclei of the stria terminalis. In sections cut at a 45 degree angle to the parasagittal plane, much of this pathway could be maintained intact, and in vitro tissue slices prepared in this orientation were used for electrophysiological studies of oxytocinergic innervation of the bed nuclei. By extracellular recording, neurons of the bed nuclei of the stria terminalis were tested for their response to exogenous oxytocin and to stimulation of the paraventricular hypothalamus. Both short latency (3-40 ms) orthodromic excitation (26/78 neurons) and longer latency (greater than 100 ms) excitation (12/78 neurons) were observed following paraventricular hypothalamic stimulation, possibly representing mono- and polysynaptic inputs, respectively. Removal of extracellular Ca2+ blocked these orthodromic responses (n = 6). Antidromic invasion was seen in a further 11/78 neurons with characteristics of constant latency (mean = 5.9 +/- 0.7 ms), high frequency following (40-80 Hz) and persistence in Ca(2+)-free medium. When tested for the effect of oxytocin (10(-7) M), none (0/11) of the antidromically activated neurons were excited, but nine of 34 of the orthodromically excited neurons (both short and long latency) responded with a marked increase in activity. In three of eight cases, the orthodromic synaptic excitation following hypothalamic stimulation could be reversibly attenuated by the receptor antagonist [d(CH2)5,D-Tyr(OEt)2,Val4,Cit8]-vasopressin (0.5 or 2.5 x 10(-6) M), further substantiating the involvement of oxytocin. These data provide anatomical and electrophysiological evidence for an oxytocinergic innervation of the bed nuclei of the stria terminalis. This pathway is discussed in terms of possible involvement in mediating the facilitatory effect of oxytocin on the milk-ejection reflex of lactating rats which has been suggested to act through this part of the limbic system.     

Neurotensin-like immunoreactivity in the brain of the chicken, Gallus domesticus

The distribution of neurons containing neurotensin in the central nervous system of the chicken was studied immunohistochemically. The majority of the neurotensin-immunoreactive (-ir) cell bodies were located in the hypothalamus. Extensive groups of labelled perikarya were found in the hypothalamic periventricular nucleus and in the magnocellular periventricular nucleus. In addition, ir-perikarya were scattered throughout the lateral hypothalamic area and in the ventromedial hypothalamic nucleus. The only extrahypothalamic site of ir-perikarya was in the region immediately under the lateral forebrain bundle. Immunoreactive fibres were detected in the hippocampus, the parahippocampal area, the hypothalamus, the region of the tractus corticohabenular and corticoseptal tracts, the median eminence, the region above the posterior commissure and in the intercollicular nucleus. The distribution pattern of the neurotensin-ir neurons suggests that neurotensin-like peptides are involved in the hypophysiotropic functions.     

The distribution of vasopressin- or oxytocin-neurons projecting to the posterior pituitary as revealed by a combination of retrograde transport of horseradish peroxidase and immunohistochemistry

The distribution of vasopressin (AVP)-containing or oxytocin (OXT)-containing neurons in the rat hypothalamus which project to the posterior pituitary was revealed by the combination of retrograde tracing of horseradish peroxidase (HRP) and immunohistochemistry. The majority of magnocellular neurons labeled with HRP were located in some of the hypothalamic nuclei, including the supraoptic nucleus and paraventricular nucleus. Many of these neurons were also immunostained by anti-AVP or anti-OXT. On the other hand, some of the immunostained neurons were not labeled with HRP in the dorso-medial and the most caudal parts of the paraventricular nucleus. These data confirmed previous reports concerning the distribution of AVP- or OXT-neurons projecting to the posterior pituitary, as a more direct visualization of both the neuropeptides and the retrogradely transported HRP in the same tissue section was attained. In addition, some of the HRP-labeled perikarya which seemed to have direct contact with the ventricular lumen were occasionally seen; its functional significance is discussed.     

Immunohistochemical localization of chemokine CXCL14 in rat hypothalamic neurons

We immunohistochemically investigated the distribution of CXCL14, also called BRAK protein in the rat hypothalamus using anti-human CXCL14 serum. CXCL14-immunoreactive somata were localized in the periventricular area and paraventricular and supraoptic hypothalamic nuclei. In the former, immunoreactive neuronal somata, confirmed by double staining with a neuronal marker, NeuN, contained diffuse CXCL14-like immunoreactivity in their perikarya. In contrast, immunoreactive somata in the latter contained immunoreactive puncta within their perikarya. Very dense immunoreactive fibers and puncta were seen in the median eminence. Dense immunoreactive fibers were seen in the arcuate nucleus and ventromedial hypothalamic nucleus. Other hypothalamic areas contained a few immunoreactive fibers and puncta. These results demonstrated for the first time that CXCL14 protein is present in a subset of hypothalamic neurons and suggest that CXCL14 participates in hypothalamic functions such as control of autonomic nervous systems and/or participates in immune cell recruitment via the median eminence.     

Immunocytochemical localization of the catecholamine-synthesizing enzymes, tyrosine hydroxylase and dopamine-β-hydroxylase, in the hypothalamus of cattle

Immunocytochemical staining for the presence of catecholamine synthesizing enzymes, tyrosine hydroxylase and dopamine β-hydroxylase, was used to characterize the regional distribution of catecholaminergic neurons in the hypothalamus and adjacent areas of domestic cattle, Bos taurus. In steers, heifers and cows, tyrosine hydroxylase-immunoreactive perikarya was located throughout periventricular regions of the third cerebral ventricle, in both anterior and retrochiasmatic divisions of the supraoptic nucleus, suprachiasmatic nucleus, and ventral and dorsolateral regions of the paraventricular nucleus, dorsal hypothalamus, ventrolateral aspects of the arcuate nucleus, along the ventral hypothalamic surface between the median eminence and optic tract, and in the posterior hypothalamus. Immunostained perikarya ranged from small (10–20 μm, parvicellular) to large (30–50 μm, magnocellular) and were of multiple shapes: round, triangular, fusiform or multipolar, often with 2–5 processes of branched arborization. There were no dopamine-β-hydroxylase immunoreactive perikarya observed within the hypothalamus and adjacent structures. However, both tyrosine hydroxylase and dopamine-β-hydroxylase immunoreactive fibers and punctate varicosities were observed throughout regions of tyrosine hydroxylase immunoreactivity perikarya. Generally, the location and pattern of hypothalamic tyrosine hydroxylase immunoreactivity and dopamine-β-hydroxylase immunoreactive were similar to those reported for most other large brain mammalian species, however, there were several differences with commonly used small laboratory animals. These included intense tyrosine hydroxylase immunoreactivity of perikarya within the retrochiasmatic division of the supraoptic nucleus (ventral A15 region), the absence of tyrosine hydroxylase immunoreactive perikarya below the anterior commissure or within the bed nucleus of stria terminalis (absence of the dorsal A15 region), an abundance of tyrosine hydroxylase immunoreactive perikarya within the ependymal layer of the median eminence, heavy innervation of the arcuate nucleus with dopamine-β-hydroxylase immunoreactive fibers and varicosities, and the paucity of dopamine-β-hydroxylase immunoreactive throughout the median eminence.     

大鼠下丘脑大细胞分泌系统内一氧化氮合酶与催产素的共存

目的　为进一步阐明一氧化氮 (NO)与催产素 (OT)在下丘脑神经内分泌调节中的作用提供形态学资料。方法　用NADPH d组织化学方法 ,并结合免疫组织化学相结合技术 ,观察大鼠下丘脑大细胞分泌系统内一氧化氮合酶 (NOS)与OT免疫阳性神经元的分布与共存关系。结果　NOS与OT在下丘脑室旁核、视上核等下丘脑各大神经分泌核区内的分布基本类似 ,并呈部分共存关系。并且初次在第三脑室室周区内观察到NOS/OT双重反应阳性触液神经元。结论　研究结果提示NO与OT在有关下丘脑生殖与性行为的神经内分泌调节活动中起着重要的介质作用。