Light and electron microscopic immunocytochemistry of neurotensin-like immunoreactive neurons in the rat hypothalamus

Neurotensin-like immunoreactive neuronal perikarya, fibers and terminals in the rat hypothalamus, particularly in the arcuate nucleus, the paraventricular nucleus and the median eminence, were investigated by light and electron microscopic immunocytochemistry. The main distributional areas of immunoreactive neuronal perikarya were found to be the arcuate nucleus, the periventricular nucleus and the paraventricular nucleus by light microscopic immunocytochemistry. Immunoreactive neuronal perikarya showed a characteristic distributional pattern in the arcuate nucleus. In the paraventricular nucleus they were distributed in both the magnocellular and parvocellular portions. A large number of immunoreactive terminals were observed throughout the external layer of the median eminence, particularly its lateral portion. A moderate number of immunoreactive terminals were also observed in the internal layer of the median eminence. By electron microscopic immunocytochemistry immunoreactive neuronal perikarya both in the arcuate and paraventricular nuclei showed generally well-developed cell organelles such as mitochondria, r-ER, and Golgi complex. In addition, immunoreactive dense granules were dispersed throughout the perikarya. A large number of immunoreactive terminals containing immunoreactive dense granules, clear vesicles and mitochondria were observed in the vicinity of pericapillary spaces of the external layer of the median eminence. This observation strongly suggests that neurotensin-like immunoreactive substance is released into the portal capillaries.     

Analysis of the ACTH/β-End/α-MSH-Immunoreactive afferent input to the hypothalamic paraventricular nucleus of rat

Immunoreactive fibers and varicosities in the hypothalamic paraventricular nucleus (PVN) were examined by light- and electronmicroscopy, following treatment of brain slices with specific antibodies to adrenocorticotropin (ACTH), β-endorphin (β-End) and α-melanotropin (α-MSH) peptides. In an attempt to provide a more precise, quantitative definition of the densities of immunoreactive elements, sections were analyzed by computer based image-analysis techniques.Fibers and varicosities immunostained with the 3 different antibodies displayed an identical distribution pattern throughout the nucleus suggesting that they are parts of the same, arcuate pro-opiomelanocortin (POMC) neuron system. Although immunoreactive varicosities were found all over the PVN, it was possible to identify a characteristic, density distribution pattern. At the ultrastructural level, immunoreactive presynaptic nerve terminals were observed forming symmetrical synaptic contacts with unlabeled dendrites. The majority of immunoreactive elements were found in the dorsal parvo- and caudal magnocellular subdivisions which give rise to long projections to the lower brainstem. Moderate density of POMC neural elements was observed in the anterior and medial (ventral portion) parvocellular subdivisions which project to the external zone of the median eminence. Only a few, widely scattered immunostained varicosities are found in the medial and lateral magnocellular subdivisions which project to the neurohypophysis. A combined lesion and immunocytochemical approach has shown that the bulk of the afferent neuronal input from arcuate POMC cells enters the PVN from a ventral direction.     

Light and electron microscopic immunocytochemistry of GRF-like immunoreactive neurons and terminals in the rat hypothalamic arcuate nuclues and median eminence

Growth hormone-releasing factor (GRF) synthesizing neuronal perikarya and terminals were investigated by light and electron microscopic immunocytochemistry using rat hypothalamus. Immunoreactive neuronal perikarya were located mainly in the ventrolateral part of the arcuate nucleus. They contained well developed cell organella such as mitochondria and rough surfaced endoplasmic reticulum with some expansion. They also contained immunoreactive dense granules (80-120 nm in diameter). On the surface of the immunoreactive neuronal perikarya were frequently found non-immunoreactive axo-somatic synapses. Therefore, the GRF-like immunoreactive neurons were assumed to receive neuronal inputs from other neurons on their neuronal soma. In the external layer of the median eminence large numbers of immunoreactive terminals were distributed particularly around the capillaries of the portal vessel. Electron microscopic immunocytochemistry revealed large numbers of immunoreactive terminals containing immunoreactive dense granules, synaptic vesicles and mitochondria in the vicinity of the basement membrane of the pericapillary space of the portal vessel. Therefore, we concluded that GRF-like immunoreactive substances are released into the portal capillaries from the nerve terminals, which originate from the neuronal perikarya in the ventrolateral part of the arcuate nucleus, and act on growth hormone release in the anterior pituitary. We also suggest that GRF-like immunoreactive neurons have abundant terminal arborization in the external layer of the median eminence.     

Distribution of immunoreactive substance P neurons in the hypothalamus and pituitary of the rhesus monkey

The distribution of immunoreactive substance P (IR-SP) neurons was examined in the hypothalamus and pituitary gland of the rhesus monkey by using the peroxidase-antiperoxidase immunocytochemical technique. Immunoreactive SP cell bodies were observed in the arcuate nucleus, in the region lateral to the arcuate nucleus, and in the median eminence (ME). Immunoreactive SP cells were also seen in the periventricular area of the dorsal tuberal region. A rich network of SP fibers was concentrated in the arcuate region, and the fiber stain was particularly dense in the external zone of the median eminence and in the external layer of the infundibular stalk. Also, substance P fibers were seen in the internal layer of the pituitary stalk and in the neural lobe of the pituitary gland. Outside the hypothalamus a dense network of IR-SP fibers was observed in the globus pallidus.     

Melanin-concentrating hormone (MCH) is colocalized with α-melanocyte-stimulating hormone (α-MSH) in the rat but not in the human hypothalamus

Melanin-concentrating hormone (MCH)-containing neurons have recently been localized in the dorsolateral region of the rat hypothalamus, an area where the second α-MSH system is found which contains only α-MSH and none of the pro-opiomelanocortin (POMC)-related peptides. In order to study the morphological relationships between the MCH and α-MSH neuronal systems, we have studied the immunocytochemical localization of both MCH and α-MSH in the rat hypothalamus. The same study was also performed in the human hypothalamus where there is only one α-MSH system which contains α-MSH as well as the other POMC-related peptides (first α-MSH system). In the rat dorsolateral hypothalamus, we could demonstrate that most neuronal cell bodies stained for MCH also contained immunoreactive α-MSH. In the human hypothalamus, neuronal cell bodies stained for MCH were observed only in the periventricular area whereas cell bodies containing α-MSH were exclusively located in the infundibular (arcuate) nucleus. In the rat, immunoelectron microscopy showed labelling for MCH in the dense core vesicles of positive neurons and double-staining techniques clearly demonstrated that both immunoreactive MCH and α-MSH could be consistently detected in the same dense core vesicles. These ultrastructural studies then suggest that these two peptides should be released simultaneously from neurons located in the rat dorsolateral hypothalamus.     

Effects of sulpiride treatment on the levels of immunoreactive β-endorphin in rat hypothalamic nuclei

The effects of sulpiride, a specific dopamine receptor antagonist, on the levels of immunoreactive β-endorphin (ir-β-END) in discrete hypothalamic nuclei of rats were investigated. Single injections of sulpiride significantly decreased the levels of ir-β-END in the nucleus arcuatus, nucleus paraventricularis and median eminence. Repeated injections of sulpiride significantly increased the levels of ir-β-END in the nucleus arcuatus, nucleus periventricularis and median eminence. These findings suggest that β-endorphinergic neurons are under dopaminergic control.     

Some cellular characteristics of somatostatin neurons and terminals in the periventricular nucleus of the rat hypothalamus and median eminence. Electron microscopic immunohistochemistry

Somatostatin neuronal perikarya and their processes, presumably dendrites, in the periventricular nucleus of the rat hypothalamus and terminals in the median eminence were observed by electron microscopic immunohistochemistry. Neuronal perikarya and processes contained immunoreactive dense granules (100-120 nm in diameter) and other cellular components such as polysomes, rER membranes occasionally showed high electron density. Few axo-somatic terminals were found on the somatostatin neurons, but we could detect a number of preterminal axons on immunoreactive processes, presumably dendrites. Therefore, we considered that somatostatin neurons receive mainly neuronal input through axo-dendritic synapses rather than through axo-somatic ones. In the somatostatin terminals in the external layer of the median eminence immunoreactivity was completely restricted on the granules.     

Distribution of β-lipotropin (β-LPH), adrenocorticotropin (ACTH) and α-melanocyte-stimulating hormone (α-MSH) in the rat brain. I. Origin of the extrahypothalamic fibers

By immunocytochemical techniques, the neuronal cell bodies containing ACTH, β-LPH and α-MSH have only been found in the area of the arcuate nucleus of the hypothalamus, whereas positive nerve fibers have been observed in many hypothalamic and extra-hypothalamic areas. The possible contribution of neurons which could be located in other brain areas has been studied in the rat by experiments involving hypothalamic deafferentation or destruction of the acurate nucleus. Fourteen days after deafferentation, no immunoreactive fibers could be detected in extrahypothalamic areas whereas the concentration of positive cell bodies and fibers remained unchanged within the hypothalamic island. In rats which had been injected in the neonatal period with monosodium glutamate (MSG), which selectively destroys the arcuate nucleus, only a few immunostained cell bodies were observed in hypothalamic region lateral to the arcuate nucleus. As compared to control animals, the concentration of immunostained fibers in both hypothalamic and extrahypothalamic regions was markedly decreased. These results strongly suggest that neuronal cell bodies producing ACTH, β-LPH and α-MSH are located in the region of the arcuate nucleus and send axonal projections into many brain areas.     

Immunohistochemical localization of γ-aminobutyric acid in the rat pituitary gland and related hypothalamic regions

The distribution on γ-aminobutyric acid (GABA) containing neurons in the rat pituitary gland and related hypothalamic areas was immunohistochemically investigaed using antibodies raised against GABA conjugated to bovine serum albumin by glutaraldehyde. A dense network of GABA-like immunoreactive fine varicose nerve fibers was observed within the posterior and intermediate lobes of the pituitary gland, surrounding endocrine cells and capillaries, but not in the anterior lobe. In the pituitary stalk, the dense varicose fibers ran along the anterior wall of the posterior lobe into the posterior and intermediate lobes. A small number of GABA-like immunoreactive cell bodies were evident in the intermediate lobe. GABA-like immunoreactive fibers occurred at low to high density in most parts of the hypothalamus. GABA-like immunoreactive neurons were observed in some regions related to the pituitary gland (such as periventricular nucleus, paraventricular nucleus, arcuate nucleus and accessory magnocellular nucleus). These results provide morphological evidence for the presence of GABAergic neurons in the rat hypothalamo-pituitary system.     

Neurotensin in the rat median eminence: the possible sources of neurotensin-like fibers and varicosities in the external layer

The possible sources of neurotensin-like immunoreactive axons in the median eminence were studied after several experimental surgical approaches including unilateral lateral retrochiasmatic area transection, midsagittal knife cut through the median eminence, complete surgical isolation of the medial basal hypothalamus and bilateral paraventricular nucleus lesions. Both immunohistochemical and radioimmunoassay data demonstrate that neurotensin-containing neuronal located in the hypothalamic arcuate nuclei represent the main source of neurotensin occurring in the external zone of the median eminence of the rat: (1) neither the complete isolation of the medial basal hypothalamus nor the transection of the major neuronal input channel to the median eminence in the lateral retrochiasmatic area altered neurotensin-like immunoreactivity in the median eminence; (2) bilateral lesioning of the paraventricular nucleus resulted in insignificant changes of neurotensin level in the median eminence; and (3) two days after lesioning the median eminence an increased amount of retrogradely accumulated neurotensin-like immunoreactivity was found in several perikarya of the arcuate nuclei due to the blockage of axonal transport in the transected fibers. Retrograde accumulation of neurotensin-like material in other cells scattered in the anterior hypothalamus (in the paraventricular, paraventricular and anterior hypothalamic nuclei) indicates that in addition to the arcuate neurons these neurons may also participate in the neurotensin innervation of the median eminence.     

Changes in the β-endorphin content of discrete hypothalamic nuclei during the estrous cycle of the rat

Concentrations of β-endorphin were measured in discrete brain nuclei of 4-day cycling rats on each day of the estrous cycle. On the afternoon of proestrus β-endorphin levels were significantly higher in median eminence and suprachiasmatic nucleus, and lower in arcuate nucleus, when compared to levels found on other days of the cycle. These changes coincided with the peak of plasma prolactin, which was blocked by prior administration of naloxone.     

Topographical distribution of pro-opiomelanocortin-derived peptides (ACTH/β-END/α-MSH) in the rat median eminence

The detailed distribution of adrenocorticotropin (ACTH), beta-endorphin (beta-END) and alpha-melanotropin (alpha-MSH) immunoreactivity was examined in the rat median eminence (ME) and pituitary stalk using light microscopic immunocytochemistry and radioimmunoassay (RIA). Nerve fibers and varicosities immunoreactive for ACTH/beta-END/alpha-MSH had identical distributions in the ME suggesting that they are part of the same arcuate proopiomelanocortin neuronal (POMC) system. The quantitative image analysis of POMC immunoreactive varicosities in the ME indicates no significant differences between the various rostro-caudal segments. In the main (preinfundibular) portion of the ME, a moderate density of immunoreactive elements was located in the lateral part of the internal zone and throughout the postinfundibular ME. Very few scattered varicosities were observed in the neurohemal (external) zone and in the pituitary stalk. By RIA, alpha-MSH is present in a substantially higher concentration than ACTH and beta-END throughout the ME. Knife cuts between the arcuate nucleus and ME indicate that proopiomelanocortin (POMC) fibers enter the ME in its whole rostro-caudal extent. Thus POMC neurons seem to provide innervation of structures in the internal zone but not in the neurohemal/external/zone where the portal capillary system is located. Moreover, the observation that the density of immunoreactive elements is substantially lower in the pituitary stalk than in the ME, suggests that the majority of immunoreactive fibers in the internal zone are not fibers of passage directed towards the neurohypophysis.     

Identification, characterization and stereotaxic mapping of intraneuronal α-melanocyte stimulating hormone-like immunoreactive peptides in discrete regions of the rat brain

A highly specific antibody to α-melanocyte stimulating hormone (α-MSH) was used to histochemically localize and biochemically identify and quantitate α-MSH immunoreactivity in nerve fibers and cell bodies of the rat brain.α-MSH-like immunoreactivity was contained in fibers throughout the brain. The distribution of α-MSH was determined by immunocytochemistry as well as by radioimmunoassay combined with microdissection techniques. High concentrations of α-MSH were contained in the nucleus interstitialis stria terminalis, the median eminence and the medial preoptic, anterior hypothalamic, periventricular, paraventricular, arcuate, dorsomedial, and posterior hypothalamic nuclei. Moderate α-MSH concentrations were noted in the amygdala, septum, central gray, dorsal raphe, and the nucleus tractus solitarius. Cell bodies containing α-MSH were observed only in the arcuate nucleus.The α-MSH-like compound in brain had similar immunochemical and electrophoretic properties of standard α-MSH but high pressure liquid chromatographic analysis demonstrated that the α-MSH-like immunoreactivity was comprised of one major and two minor components. The major immunoreactive peak had an identical retention time as α-MSH and therefore may be chemically identical to α-MSH. The similar retention times and immunoreactivity of the other two compounds suggest a similarity in size and structure to α-MSH. These observations demonstrate that fibers containing α-MSH emanate from the arcuate nucleus to innervate many other regions of the rat brain.     

Immunocytochemical distribution of [Met]enkephalin-Arg-Gly-Leu immunoreactivity in the rat diencephalon

Recently, [Met]Enkephalin-Arg-Gly-Leu (MEAGL) was isolated from bovine adrenal glands, and it was found to be derived exclusively from proenkephalin. Therefore, we investigated the distribution of MEAGL-like immunoreactive neuronal perikarya and fibers in the rat diencephalon pretreated with colchicine by PAP immunocytochemistry. In the thalamus MEAGL immunoreactive neuronal perikarya were distributed in the paraventricular nucleus and the ventral part of the lateral geniculate nucleus. Immunoreactive fibers were found in the paraventricular, paracentral, anteroventral, reuniens and rhomboid nuclei. In addition, immunoreactive fibers were also noted in the anterior pretectal nucleus. In the hypothalamus, immunoreactive neuronal perikarya were observed in the medial preoptic area, anterior and lateral hypothalamic nuclei, perifornical region, parvocellular and postero-magnocellular regions of paraventricular nucleus, ventromedial nucleus, dorsomedial nucleus, arcuate nucleus, premammillary, medial mammillary and lateral mammillary nuclei. The distribution of immunoreactive fibers was similar to that of neuronal perikarya. However, immunoreactive fibers were also observed in the supraoptic and suprachiasmatic nuclei where no immunoreactive neuronal perikarya were detected. Numerous immunoreactive fibers were detected in the external layer of the median eminence, but there were few in the internal layer. The similarity and difference in the distribution between MEAGL and other proenkephalin peptides such as [Met]enkephalin were also discussed.     

Coexpression of dynorphin and neurokinin B immunoreactivity in the rat hypothalamus: Morphologic evidence of interrelated function within the arcuate nucleus

Considerable evidence suggests that dynorphin and neurokinin B (NKB) neurons in the hypothalamic arcuate nucleus participate in the sex-steroid regulation of reproduction. In the present study, we used dual-label immunofluorescence to explore the distribution of prodynorphin and proNKB immunoreactivity in the rat hypothalamus. Additionally, we investigated whether arcuate prodynorphin-ir (immunoreactive) neurons expressed the neurokinin 3 receptor (NK3R) or nuclear estrogen receptor-alpha (ERalpha). We found that the majority of prodynorphin-ir neurons in the rat arcuate nucleus expressed proNKB, whereas nearly all (99%) of the proNKB neurons were immunoreactive for prodynorphin. The arcuate nucleus was the only site in the hypothalamus where neuronal somata coexpressing prodynorphin and proNKB-immunoreactivity were identified. A dense plexus of double-labeled prodynorphin/proNKB-ir fibers was found within the arcuate nucleus extending to the median eminence and throughout the periventricular zone of the hypothalamus. Prodynorphin/proNKB fibers were also identified in the paraventricular nucleus, anterior hypothalamic area, medial preoptic area, median preoptic nucleus, anteroventral periventricular nucleus, and bed nucleus of the stria terminalis in a distribution consistent with previously described arcuate nucleus projections. Interestingly, the majority of prodynorphin-ir neurons in the arcuate nucleus expressed NK3R, and nearly 100% of the prodynorphin-ir neurons contained nuclear ERalpha. Our results suggest that there is a close functional relationship between dynorphin and NKB peptides within the arcuate nucleus of the rat, which may include an autofeedback loop mediated through NK3R. The diverse hypothalamic projections of fibers expressing both prodynorphin and proNKB provide evidence that these neurons may participate in a variety of homeostatic and neuroendocrine processes.     

Development and regulation of β adrenergic receptors in kitten visual cortex: An immunocytochemical and autoradiographic study

The developmental pattern and laminar distribution of β₁ and β₂ adrenergic receptor subtypes were studied in cat visual cortex with autoradiography using [¹²⁵I]iodocyanopindolol as a ligand and also with immunocytochemistry using a monoclonal antibody directed against β adrenergic receptors. In the primary visual cortex of adult cats, the laminar distributions of both β₁ and β₂ adrenergic receptors revealed by autoradiography were very similar, with concentrations in layers I, II, III and VI. In young kittens (postnatal days 1 and 10), fewer β adrenergic receptors were present, and they were concentrated in the deep cortical layers (V–VI) and subcortical white matter. Between postnatal days 15 and 40, β adrenergic receptors increased in density more quickly in the superficial layers than they did in the deep and middle cortical layers. By postnatal day 40, the adult pattern was achieved, with two bands of intense binding in the superficial and deep cortical layers and a lower density in layer IV. Immunocytochemical techniques applied to adult cat cortex showed that β adrenergic receptor-like immunoreactivity was found in different populations of neurons and glial cells. The immunoreactive neural cells were most dense in layers II, III and VI. About 50% of these immunoreactive neural cells were glial cells, primarily astrocytes. Immunoreactive pyramidal cells were mostly located in layers III and V. In layer IV, many stellate cells were stained. Immunoreactive astrocytes in the subplate and white matter progressively increased in number during development until adulthood. The pattern of laminar distribution and the developmental process was not affected by interrupting noradrenergic innervation from locus ceruleous either before or after the critical period. However, when visual input was interrupted by lesions of the lateral geniculate nucleus in young kittens (postnatal day 10), the density of both β adrenergic receptor subtypes decreased significantly in the deep cortical layers. Lateral geniculate nucleus lesions in adult cats resulted in a pronounced decrease in β adrenergic receptor density in layer IV.     

Immunohistochemical localization of avian pancreatic polypeptide-like immunoreactivity in the rat hypothalamus

The distribution of avian pancreatic polypeptide-like (APP) immunoreactivity within the rat hypothalamus was investigated with the indirect immunoperoxidase method. APP immunoreactive perikarya are found in largest numbers in the retrochiasmatic area, the arcuate nucleus, and the supracommissural portion of the interstitial nucleus of the stria terminalis. Small clusters of immunoreactive neurons are also consistently observed in the ventral aspect of the medial preoptic area and lateral hypothalamic area, immediately dorsolateral to the optic chiasm and tracts. These neurons are apparent in all animals but are more intensely strained and occur in larger numbers following colchicine pretreatment. Other immunoreactive neurons are visible only in colchine-treated rats and are scattered throughout the anterior and lateral hypothalamic areas and the supramammillary nucleus. Immunoreactive axons and terminal fields present an extensive and highly characteristic distribution throughout the hypothalamus, which in many instances exhibits differential distribution within specific subfields of hypothalamic nuclei and areas. The heaviest concentrations of APP immunoreactive axons are present in the periventricular nucleus throughout the rostrocaudal extent of the hypothalamus, the ventrolateral portion of the suprachiasmatic nucleus, the retrochiasmatic area, the parvocellular paraventricular nucleus, the ventral supraoptic nucleus, the perifornical nucleus, the ventral dorsomedial nucleus, and the arcuate nucleus. Moderate plexuses of immunoreactive fibers are also present in the medial preoptic area, the anterior and lateral hypothalamic areas, the nucleus circularis, the median eminence, and the ventral premammillary area. Other areas, such as the ventromedial nucleus, contain virtually no immunoreactive axons but are encapsulated by a dense plexus of immunoreactive terminals. The distribution of a major component of APP immunoreactive fibers exhibits a marked similarity to that of previously described norepinephrine-containing hypothalamic afferents. Other groups of APP immunoreactive perikarya and fibers appear to represent components of intrinsic diencephalic systems.     

Distribution of neuropeptide Y-like immunoreactivity in the hypothalamus of the adult golden hamster

The distribution of neuropeptide Y (NPY)-like immunoreactivity within the hypothalamus of the adult golden hamster was investigated with conventional immunohistochemical techniques. Neuropeptide Y immunoreactive cell bodies were found in greatest numbers in the arcuate nucleus while a few stained perikarya were seen in the internal and subependymal zones of the median eminence. Isolated perikarya were observed in the anterior commissure and supracommissural portion of the interstitial nucleus of the stria terminalis. Immunoreactive axons were located throughout the hypothalamus with the highest concentrations in the subependymal and internal zones of the median eminence, the interstitial nucleus of the stria terminalis, the medial preoptic area, and in the following nuclei: periventricular, suprachiasmatic, paraventricular, perifornical, median preoptic, and arcuate. Moderate to dense plexuses of immunoreactive fibers were observed in the anterior, lateral, and posterior hypothalamic areas and in the infundibular stalk. The supraoptic nucleus and lateral preoptic area displayed a small number of labeled axons whereas the ventromedial nucleus contained only a few fibers. NPY immunoreactive fibers were present in the optic tract and in the dorsomedial aspect of the optic chiasm. Labeled fibers penetrated the ependymal lining of the third ventricle throughout the ventral aspect of the periventricular zone. Additional fibers were observed in the pia lining the ventral aspect of the hypothalamus. This systematic analysis of hypothalamic NPY immunoreactivity in the adult golden hamster suggests that a portion of the labeled fibers display a distribution that is similar to previously described noradrenergic fibers in the hypothalamus.     

Distribution of immunoreactive growth hormone releasing factor (1–44)NH2 in the tuberoinfundibular system of the rhesus monkey

Using an antiserum which reacts with the carboxyl terminus of GRF(1-44)NH2, the distribution of immunoreactive growth hormone releasing factor (GRF) in the rhesus monkey hypothalamus was delineated by peroxidase immunocytochemistry. Immunoreactive material was present in dense terminal fields in the median eminence closely associated with portal capillaries but in a location distinct from that noted for immunoreactive thyrotropin-releasing hormone (TRH) or somatostatin. GRF-immunoreactive cell bodies were identified in the arcuate nucleus and ventromedial nucleus. These studies provide evidence for the presence of GRF(1-44)NH2 in the primate brain and demonstrate that in the hypothalamus it is localized exclusively in cells and fibers corresponding to the tuberoinfundibular system.     

Distribution of interleukin 1β immunoreactivity within the porcine hypothalamus

The presence and localization of interleukin 1β immunoreactivity (IL 1β i.r.) was studied in the hypothalamus of four healthy, male pigs at 7 months of age, using immunocytochemical techniques on 100 μ vibratome and 10 μ paraffine sections. IL 1β i.r. was found in neuronal cell bodies and their processes within nuclei and fiber of the fiber tracts of the hyphotalamus as well as in varicose fibers, terminals and deposits within the median eminence. In addition, IL 1β i.r. was found in the walls of several, but not all, blood vessels and in very few glial cells.