Changes induced by formalin in the hypothalamic neurosecretory system of the spotted owlet, Athene brama temminck.

Histological changes induced in the HNS of the spotted owlet, Athene brama Temminck, by injection of 1 ml 5 or 10% formalin are described. No difference could be detected in the response of the HNS to 5 or 10% formalin administration. In the HNS of birds killed within 5 min of formalin administration, there was only partial depletion of NSM from the neurons, the tract and the NL; the quantity of NSM in the AME remained more or less unchanged. In animals killed 10-90 min after formalin injection, the depletion of NSM from the neurons, the tract and the NL was more complete. The neurons of the preoptic division of the SON exhibited the maximum response; these neurons were also moderately hypertrophied. The NL also was hypertrophied in some animals; the NSM in the AME registered only a partial loss. The interval between formalin administration and killing did not influence the degree of changes in the HNS. The depletion of NSM was no greater at 90 min following formalin injection than at 10 min. Since it is well established that formalin stress causes augmented secretion of ADH and that there is a close functional relationship existing between ADH and NSM, the depletion of NSM noticed in the HNS of the spotted owlet following formalin administration is interpreted as indicating augmented secretion of ADH. Hence it seems that the response of the HNS of birds to formalin stress are comparable to those of the HNS of mammals. The results thus provide histological evidence in favour of the concept that stressful stimuli cause increased secretion of ADH.     

Localization of arginine vasotocin (AVT) mRNA in extrasomal compartments of magnocellular neurons in the chicken hypothalamo-neurohypophysial system

In the chicken, arginine vasotocin (AVT) is produced in and secreted by magnocellular neurons in the supraoptic (SON) and paraventricular (PVN) nuclei. To test the hypothesis of axonally transported AVT mRNA, the localization of AVT mRNA within extrasomal, axonal/dendritic compartments in the chicken hypothalamo-neurohypophysial system (HNS) were examined using AVT specific in situ hybridization histochemistry (ISHH) and RT-PCR. Many perikarya in the PVN and external--but none in the ventral subgroup of the SON show ISHH signals clearly extended into one or two processes, some with branching collaterals, traceable over a distance of more than 100 microns. Furthermore by using RT-PCR, AVT mRNA was detected in the median eminence and neurohypophysis representing the distal parts of the HNS, mainly consisting of axons and/or axon terminals. These observations of axonal mRNA offer new insights to the organization and function of the avian HNS.     

Radioautographic studies on the neurohypophysial projections of the supraoptic and paraventricular nuclei in the rat

Summary The distribution of labelled axonal pathways was studied after unilateral stereotaxic injection of ³H-leucine into either supraoptic (SON) or paraventricular nuclei (PVN). In addition to extrahypothalamic projections of both nuclei, the main efferents appeared to run towards the neurohypophysis, yet with a strikingly different pattern. At the neurohypophysial level, the SO-neurohypophysial tract crossed the inner layers of the median eminence (ME) before scattering in the neural lobe. The PV-neurohypophysial pathway, by contrast, provided an exclusive innervation to the external layer of the whole neurohypophysial organ, including the median eminence, infundibular stalk and neural lobe. The functional correlates of the clear-cut anatomical distinctness between the two magnocellular neurosecretory systems are discussed.     

Reactivity pattern of vasopressin-containing neurons and its relation to the antipyretic reaction in the pregnant guinea pig

Summary Changes in the content of vasopressin-immunoreactive material in neurons and their projections were examined in pregnant and nonpregnant guinea pigs as well as in mother and newborn animals. Before sacrifice all animals used in the present study were submitted to a pyrogen test, during which the pregnant animals displayed a reduced fever response to exogenous pyrogen. The unlabeled enzyme-immunoperoxidase method was used in the present study. Light microscopic examination showed that, in comparison to all other groups examined, the pregnant animals exhibited a reduced content of the vasopressin-immunoreactive substance in the supraoptic nucleus (SON), in the neuronal pathways extending between the paraventricular nucleus (PVN) and the SON, as well as in the axons projecting to the neural lobe of the pituitary. An increased amount of vasopressin-immunoreactive material was observed during pregnancy especially in the medial portion of the PVN, in axonal distensions in the external zone of the median eminence and in the extrahypothalamic projection sites of the PVN in the lateral septum and in the amygdala. In the pregnant animals neurovascular contacts of vasopressinergic perikarya and fibers were abundant in the PVN; in the lateral septum and in the amygdala vasopressinergic terminals appeared to contact neurons of other types. It is suggested from the present immunocytochemical results that activation of neurons in the medial portion of the PVN and the increased number of vasopressinergic terminals and preterminals in the lateral septum and in the amygdala might be functionally involved in fever suppression at the term of pregnancy.     

Microarray analysis reveals interleukin-6 as a novel secretory product of the hypothalamo-neurohypophyseal system

Physiological activation of the hypothalamo-neurohypophyseal system (HNS) by dehydration results is a massive release of vasopressin (VP) from the posterior pituitary. This is accompanied by a functional remodeling of the HNS. In this study we used cDNA arrays in an attempt to identify genes that exhibit differential expression in the hypothalamus following dehydration. Our study revealed nine candidate genes, including interleukin-6 (IL-6) as a putative novel secretory product of HNS worthy of further analysis. In situ hybridization and immunocytochemistry confirmed that IL-6 is robustly expressed in the supraoptic (SON) and the paraventricular (PVN) nuclei of the hypothalamus. By double staining immunofluorescence we showed that IL-6 is largely co-localized with VP in the SON and PVN. In situ hybridization, immunocytochemistry, and Western blotting all revealed IL-6 up-regulation in the SON and PVN following dehydration, thus validating the array data. The same dehydration stimulus resulted in an increase in IL-6 immunoreactivity in the axons of the internal zone of the median eminence and a marked reduction in IL-6-like material in the posterior pituitary gland. We thus suggest that IL-6 takes the same secretory pathway as VP and is secreted from the posterior pituitary following a physiological stimulus.     

Fos protein expression in mouse hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei upon osmotic stimulus: colocalization with vasopressin, oxytocin, and tyrosine hydroxylase

The quantity and topography of activated vasopressin (AVP), oxytocin (OXY), and tyrosine hydroxylase (TH) neurons were studied immunohistochemically in the anterior, middle, and posterior portions of the PVN and SON in mice 60 min after a single injection of hypertonic saline (HS, 400 microl 1.5M, i.p.). Fos-neuropeptide double-stainings revealed: (1) Fos expression in each portion of the PVN and SON; (2) maximal number of Fos-AVP (79 cells) and Fos-OXY (50 cells) double-labelings in the middle portion of the PVN; (3) low number of Fos-TH perikarya in the PVN and their lack in the SON; (4) similar incidence (around 50%) of Fos-AVP and Fos-OXY perikarya in the SON; and (5) presence of activated AVP, OXY, and TH neurons in the periventricular, subependymal, and sub-PVN zones of the PVN. Topographic analysis revealed that the majority of AVP neurons expressing Fos occupied the dorsolateral and central part of the middle portion of the PVN. In the same PVN portion, Fos-OXY neurons occurred in similar frequency, however, they were primarily distributed along the lateral and medial margins of the PVN. In the SON, Fos-OXY cells occupied mainly its dorsal, while Fos-AVP cells predominated in its ventral part. The data clearly indicate that HS is not a selective stimulus neither for PVN nor SON itself and provide evidence that both PVN and SON AVP and OXY cells play important role in the mediation of signals induced by HS. In addition, the limited number of AVP, OXY, and TH neurons activated by HS may account for their differential functional specializations selective for stress/osmotic circuits activated by HS.     

Catecholamine biosynthesis and vasopressin and oxytocin secretion in the spontaneously hypertensive rat: an in vitro study of localized brain regions

The in vitro synthesis of catecholamines and the secretion of vasopressin (AVP) and oxytocin (OT) was measured in localized regions of the hypothalamo-neurohypophyseal system in the spontaneously hypertensive rat (SHR). The posterior pituitary (PP), median eminence (ME) and supraoptic (SON) and paraventricular (PVN) nuclear regions were incubated in vitro in media containing 3H-tyrosine. Media and tissue levels of AVP and OT were measured as well as norepinephrine and dopamine content and biosynthesis. There were no differences in peptide release in either the PP, ME or SON. However, there was a marked increase in peptide release from the PVN of the SHR. Media AVP levels were 0.3 pg/ml/micrograms protein in the WKY as compared to 2.1 pg/ml/micrograms protein in the SHR. OT release was increased 2 fold, from 0.85 to 1.7 pg/ml/micrograms protein. PVN content of both AVP and OT was significantly lower in the SHR. ME and SON peptide levels were not changed, while neurohypophyseal AVP levels were increased in the SHR. With regard to the catecholamines appreciable norepinephrine synthesis was measured in the PVN and SON while there was little 3H-norepinephrine in the ME or PP. In the hypertensive rat, there was an increase in norepinephrine synthesis in the PVN with no change in the SON. These results provide further support for fundamental changes in the catecholaminergic and peptidergic systems of the hypothalamo-neurohypophyseal axis of the SHR.     

巴基斯坦旁遮普中部横斑腹小鸮的食性

横斑腹小鸮(Athene brama)是巴基斯坦旁遮普中部农业生态系统中最常见但研究匮乏的猛禽。我们通过分析吐弃块(n=498)以了解其季节性和地域性食性变化。结果显示:小型哺乳类占所有食物生物量的98.4%,而昆虫类在数量上占据绝对优势(56.4%)。在小型哺乳类食物中,鼠类(38.8%)是稳定的食物成分。而在昆虫食物中,甲虫最多(42.8%)。横斑腹小亦捕食鼩鼱类(2.3%)和鸟类(1.7%)。昆虫类食物还有蟑螂(6.4%)、臭虫(3.3%)、蝗虫(6.7%)和蚂蚁(3.2%)。小家鼠(Mus musculus)和柔毛鼠(Rattus meltada)在鼠类食物中出现频次最多。不同地区中,Hafizabad的食物多样性最高(2.07),而秋季的食物多样性最高(1.99)。     

Neural Connections Between Prosencephalic Structures Involved in Vasopressin Release

1. The diagonal band (DB) and the lateral septal area (LSA) are two prosencephalic structures, which were implicated in vasopressin release.2. The present experiment was designed to investigate neural connections between the DB and the LSA and from these nuclei to the paraventricular (PVN) and supraoptic (SON) nuclei, which could be related to vasopressin release.3. For the above purpose the bidirectional neuronal tracer biotinylated dextran amine (BDA) was injected into the DB or the LSA of male Wistar rats. Five days later the animals were sacrificed and brain slices were processed and analyzed to determine neuronal projections efferent from as well as afferent to these structures.4. Neuronal staining was more prominent in regions ipsilateral to the BDA injection site.5. After BDA injections into the DB, efferent projections from the DB were observed at the LSA, the PVN, the prefrontal cortex, the mediodorsal thalamic nucleus, and throughout the anterior hypothalamus, but not at the SON. At the PVN, labeled varicose fibers were observed at the magnocellular portion. The DB was found to receive a massive input from the LSA. More discrete projections to the DB were originated at the prefrontal cortex and from hypothalamic neurons outside the PVN and the SON.6. After BDA injections into the ventral portion of the LSA, efferent projections from the LSA were intense at the DB and throughout the hypothalamus. Labeled fibers were observed at the structures surrounding the SON or the PVN but not within those nuclei.7. The results indicate a massive neural output from the LSA to the DB and the existence of a direct neural connection from the DB to the PVN. No direct connections were observed between the LSA and the magnocellular nuclei (PVN and SON) or between the DB and the SON.     

The paraventriculo-infundibular corticotropin releasing factor (CRF) pathway as revealed by immunocytochemistry in long-term hypophysectomized or adrenalectomized rats

The immunocytochemical localization of corticotropin releasing factor (CRF)-containing pathways projecting from the paraventricular nucleus (PVN) to the external layer of the median eminence (ME) in long-term hypophysectomized or adrenalectomized rats is described. Immunocytochemistry was followed by silver intensification of the diaminobenzidine end-product. In comparison with untreated control rats, both hypophysectomy and adrenalectomy resulted in a dramatic increase in immunostaining of the CRF-containing perikarya and fibers, particularly those originating from the PVN and terminating in the ME. The staining was more intense in adrenalectomized than in hypophysectomized rats. The CRF-positive fibers emerging from the PVN form a medial, an intermediate and a lateral fiber pathway. The lateral and intermediate CRF tracts leave the dorsolateral part of the PVN and course laterally and medially of the fornix, respectively, then ventrally toward the optic tract. Just dorsal to the optic tract they turn in caudal direction and run parallel with and very close to the basal surface of the hypothalamus; individual fibers then turn medially to terminate in the external layer of the ME. Only a few fibers originate from the medial-ventral part of the PVN (medial pathway). These fibers run in ventral direction along the walls of the 3rd ventricle and terminate in the ME. Thus the majority of CRF fibers, similarly to other peptidergic systems, reach the medial basal hypothalamus from the anterolateral direction.     

中国树鼩下丘脑视上核和室旁核内加压素和催产素能神经元的比较分布

应用PAP-PAAP双重免疫组化染色程序在同一切片上进行两种肽能物质的定位,观察了中国树鼩下丘脑视上核和室旁核内VP能和OT能神经元的比较解剖学分布,发现:视上核被视束分成主部和交叉后部。在视上核主部,其头侧部几乎仅含OT能神经元胞体,中间部VP能胞体出现并逐渐增多,尾侧部VP能胞体数目明显超过OT能胞体。在明显含有两种胞体的中间部和尾侧部,OT能胞体多位于背内侧,VP能胞体多位于腹外侧;在视上核交叉后部,其头侧部以VP能胞体为主,且多位于背外侧,OT能胞体多位于腹内侧。中间部OT能胞体多位于内侧,VP能胞体多位于外侧。尾侧部OT能胞体多位于背、腹两侧,VP能胞体则多位于中间;在室旁核,其头侧部几乎全由OT能胞体构成。中间部,VP能胞体出现并逐渐增多,OT和VP能胞体分别主要位于内、外侧。尾侧部两种神经元胞体较明显地分为内、外两群,内侧群主要为OT能胞体,外侧群几乎全为VP能胞体,该群的头侧半又可分为背腹两个亚群,至尾侧半,此二亚群渐合并。本文讨论了OT和VP能神经元在中国树鼩和大鼠视上核和室旁核内的比较分布。     

Osmotic regulation of substance P and neurokinin A peptide content and substance P binding sites in distinct hypothalamic nuclei of the rat.

Quantitative receptor autoradiography using Bolton-Hunter iodinated substance P (SP) was used to localize specific sites in the rat hypothalamus. The amount of SP and neurokinin A (NkA) in extracts from discrete areas of the hypothalamus was measured using specific radioimmunoassays. A high density of SP binding sites was observed in the perimeter of the magnocellular paraventricular and supraoptic nuclei, while the magnocellular nuclei themselves possessed a low receptor density. In control animals, the number of SP binding sites was also low in the arcuate nucleus and the median eminence. Substance P and NkA peptide concentrations were highest in the paraventricular nucleus (PVN), decreasing in the following order: arcuate nucleus (Arc) greater than median eminence (ME) greater than supraoptic nucleus (SON) greater than subfornical organ (SFO). In animals given 340 mmol/l NaCl instead of tap water to drink for 12 days, significant increases in the number of SP binding sites occurred in the medial parvocellular subdivision of the PVN, periamygdaloid cortex, medial preoptic nucleus, Arc, and ME, but other hypothalamic areas were unaffected. In saline-treated animals, significant increases in SP and NkA peptide concentrations were observed in the ME, while in the SFO only the concentration of NkA increased significantly. In the SON, substance P and neurokinin A levels were doubled, whereas in the PVN and Arc no changes in peptide levels were observed. Chronic osmotic stimulation is associated with lowered circulating levels of adrenocorticotropin releasing hormone (ACTH), and the present data further substantiate the hypothesis that hypothalamic tachykinin-containing neuronal terminals are centrally involved in the inhibition of anterior pituitary ACTH release observed during chronic osmotic stimulation.     

Colchicine Treatment Differently Affects Releasable Thyrotropin-Releasing Hormone (TRH) Pools in the Hypothalamic Paraventricular Nucleus (PVN) and the Median Eminence (ME)

1. Hypophysiotropic thyrotropin-releasing hormone (TRH) is synthesized in the hypothalamic paraventricular nucleus (PVN) and transported to the median eminence (ME) where it enters the hypophyseal portal blood. TRH in the ME is situated exclusively in nerve terminals, whereas TRH in the PVN and septum is of extrinsic (nerve terminals) as well as intrinsic (perikarya) origin. 2. To determine the source and possible differential regulation of TRH release from these structures, we blocked TRH axonal delivery by i.c.v. administration of colchicine into the lateral cerebral ventricle of euthyroid or hypothyroid rats in doses of 7.5 μg or 7.5, 75 and 100 μg, respectively, two days prior to the evaluation of the TRH secretion from the PVN, ME and the septum in vitro. 3. In euthyroid rats a low dose of colchicine did not significantly affect plasma TSH. The secretory response to both ethanol in an isosmolar medium and a high K⁺ in the ME as well as the PVN explants was well preserved. However, colchicine treatment resulted in the significant increase of basal secretion of TRH from the PVN. 4. Hypothyroidism induced by 200 mg/l methimazole in drinking water for two weeks resulted in growth arrest, elevated plasma thyrotropin and decreased TRH content in the PVN and the ME. Colchicine partially decreased elevated plasma thyrotropin and increased the TRH content in the PVN and its basal release in vitro which was independent of extracellular Ca²⁺. Interestingly, a TRH release from the PVN could not be further stimulated either by K⁺ membrane depolarization or by ethanol. TRH responsiveness to the stimulation remained unaffected in the ME. The effect of colchicine on the septal TRH secretion was intermediate between the effect observed in the PVN and the ME. 5. In conclusion, the absence of a TRH secretory response to stimuli in the PVN after colchicine disruption of the microtubules and Golgi system suggests that stimulated TRH release observed from the PVN explants in vitro occurs from nerve terminals projecting to the PVN from other brain regions. The independence from extracellular calcium implies that TRH released under the non-stimulating conditions occurs most likely via the constitutive secretory pathway from dendrites and/or perikarya. Regulation of septal TRH is markedly different from the hypophysiotropic one. An erratum to this article is available at .     

Distribution pattern in the human pituitary and hypothalamus of a new neuropeptide: The C-terminal glycoprotein-fragment of human pro-pressophysin (CPP)

Summary The distribution pattern of CPP-containing neurons and fibers in the human pituitary and hypothalamus was studied with a specific antiserum to human CPP and the unlabeled antibody technique. Immunoreactive CPP was found in the magnocellular neurons of the supraoptic nucleus (SON), the paraventricular nucleus (PVN) and in neurons scattered in the supraoptic hypophyseal tract. CPP-containing parvocellular neurons were found in the suprachiasmatic nucleus (SCN). The CPP-containing fibers from the magnocellular neurons formed a tract coursing through the median eminence and the pituitary stalk to the posterior lobe of the hypophysis. In contrast, no such fibers from the SCN projected to SON, PVN and the median eminence. This pattern is identical to that of vasopressin and its associated neurophysin-containing neurons and fibers and strongly supports the concept that CPP is a part of the common precursor for vasopressin and neurophysin II. The biological importance of human CPP other than being a precursor fragment remains to be elucidated.To whom requests for reprints should be addressed     

Activation of vasopressinergic and oxytocinergic neurons during aging in the Wistar rat

The activity of the hypothalamo-neurohypophyseal system (HNS) was determined in male Wistar rats from 3 to 32 months of age. Plasma levels of vasopressin (AVP) and oxytocin (OXT) were measured by means of a radioimmunoassay. In addition, the distribution of the Golgi apparatus marker enzyme thiamine-pyrophosphatase (TPP-ase) was measured as a parameter for neurosecretory activity in the hypothalamic supraoptic and paraventricular nuclei (SON and PVN). Plasma levels of radioimmunoassayable AVP were increased in the 32-month-old animals. Plasma levels of radioimmunoassayable OXT in 32-month-old animals did not differe from the levels found in the youngest group, but were higher than in 11-month-old animals. Neurosecretory activity in the SON was similar in 3- and 32-month-old animals, whereas in the PVN neurosecretory activity was increased in the 32-month-old animals. Urine excretion decreased between 6 and 11 months of age and remained on the same level until 32 months of age. In other words, instead of a loss of HNS function as has been suggested in the literature, an increased neurosecretory activity was observed in aged rats.     

Ultrastructural immunohistochemical localization of vasopressin in the hypothalamic-neurohypophysial system of three murids

Vasopressin was immunohistochemically localized at the electron microscopic (EM) level in the hypothalamic-neurohypophysial system (HNS) of three murids. Antiserum to vasopressin was produced in rabbits injected with lysine vasopressin (LVP) conjugated to egg albumin (EA), anti-EA being precipitated prior to staining. Sternberger's unlabeled antibody peroxidase technique was employed, immunoreactivity being designated by peroxidase anti-peroxidase (PAP) molecules and electron opacity. Immunoreactive neurosecretory granules (NSG) were found in the perikarya of the supraoptic nucleus (SON) in all three murids investigated, although far more profusely in the two wild strains. Immunoreactive axonal NSG were observed in the inner and outer zones of the median eminence (ME), and within most of the axons and terminals in the neurohypophysis. The concentration of primary serum effective for staining the SON (110–150) was far higher than that required for the ME and the neurohypophysis (1:500–1:1,200). AntiLVP also induced electron opacity of granules in cells of the pars intermedia (PI). Discussion centers on the significance of immunoreactive NSG in the neurosecretory (NS) perikarya, on the possibility of an extragranular pool of hormone, and on speculation about the electron opacity of the PI granules.     

Distribution of beacon immunoreactivity in the rat brain

Beacon is a novel peptide isolated from the hypothalamus of Israeli sand rat. In the present study, we determined the distribution of beacon in the rat brain using immunohistochemical approach with a polyclonal antiserum directed against the synthetic C-terminal peptide fragment (47-73). The hypothalamus represented the major site of beacon-immunoreactive (IR) cell bodies that were concentrated in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON). Additional immunostained cells were found in the septum, bed nucleus of the stria terminalis, subfornical organ and subcommissural organ. Beacon-IR fibers were seen with high density in the internal layer of the median eminence and low to moderate density in the external layer. Significant beacon-IR fibers were also seen in the nucleus of the solitary tract and lateral reticular formation. The beacon neurons found in the PVN were further characterized by double label immunohistochemistry. Several beacon-IR neurons that resided in the medial PVN were shown to coexpress corticotrophin-releasing hormone (CRH) and most labeled beacon fibers in the external layer of median eminence coexist with CRH. The topographical distribution of beacon-IR in the brain suggests multiple biological activities for beacon in addition to its proposed roles in modulating feeding behaviors and pituitary hormone release.     

Somatostatin-containing fibers and neurophysin-containing fibers in the median eminence of the fox, as seen with a double staining cytoimmunoenzyme technique]

In the external layer of the median eminence of the fox, the somatostatin-containing fibers and neurophysin-containing fibers of the hypothalamo-infundibular tract are located in distinct areas. In the neural lobe, somatostatin-positive areas are simultaneously neurophysin-positive. Outside the SON and PVN, some somatostatin-positive and neurophysin-negative perikarya are scattered close to the third ventricle. These facts suggest the existence of two somatostatin systems: a hypothalamo-infundibular (neurophysin-negative) one and a hypothalamo-neurohypophyseal (neurophysin-positive) one.     

Regulatory mechanism of the arginine vasopressin-enhanced green fluorescent protein fusion gene expression in acute and chronic stress

Various kinds of stress cause neuroendocrine responses such as corticotropin-releasing hormone (CRH) or arginine vasopressin (AVP) release from parvocellular division of the paraventricular nucleus (PVN) and activation of the hypothalamo-pituitary adrenal (HPA) axis. We examined the effects of acute and chronic stress on the expression of the AVP-enhanced green fluorescent protein (eGFP) fusion gene in the hypothalamus, using chronic salt loading as an osmotic stimulation, intraperitoneal administration of lipopolysaccharide (LPS) as acute inflammatory stress and adjuvant arthritis (AA) as chronic inflammatory/nociceptive stress. Salt loading caused a marked increase in the eGFP gene expression and eGFP fluorescence in the supraoptic nucleus, magnocellular division of the PVN and internal layer of the median eminence (ME). Administration of LPS caused increased fluorescence in parvocellular division of the PVN and external layer of the ME. AA rats revealed an increased expression of the eGFP gene and eGFP fluorescence in both magnocellular and parvocellular divisions of the PVN and both internal and external layers of the ME. On the other hand, the levels of the CRH gene expression in parvocellular division of the PVN were significantly decreased as AA developed, though plasma concentrations of corticosterone were significantly increased. These results indicate that AVP-eGFP transgenic rats enable the detection of changes in AVP expression more easily than by using procedures such as immunohistochemistry. We propose that AVP-eGFP transgenic rats represent a useful animal model for further understanding of the physiology of AVP expression in the hypothalamo-pituitary system under various physiological conditions, including various kinds of stress.     

Oxytocin and vasopressin involved in restraint water-immersion stress mediated by oxytocin receptor and vasopressin 1b receptor in rat brain

Aims

Vasopressin (AVP) and oxytocin (OT) are considered to be related to gastric functions and the regulation of stress response. The present study was to study the role of vasopressinergic and oxytocinergic neurons during the restraint water-immersion stress.

Methods

Ten male Wistar rats were divided into two groups, control and RWIS for 1h. The brain sections were treated with a dual immunohistochemistry of Fos and oxytocin (OT) or vasopressin (AVP) or OT receptor or AVP 1b receptor (V_1bR).

Results

(1) Fos-immunoreactive (Fos-IR) neurons dramatically increased in the hypothalamic paraventricular nucleus (PVN), the supraoptic nucleus (SON), the neucleus of solitary tract (NTS) and motor nucleus of the vagus (DMV) in the RWIS rats; (2) OT-immunoreactive (OT-IR) neurons were mainly observed in the medial magnocellular part of the PVN and the dorsal portion of the SON, while AVP-immunoreactive (AVP-IR) neurons mainly distributed in the magnocellular part of the PVN and the ventral portion of the SON. In the RWIS rats, Fos-IR neurons were indentified in 31% of OT-IR neurons and 40% of AVP-IR neurons in the PVN, while in the SON it represented 28%, 53% respectively; (3) V_1bR-IR and OTR-IR neurons occupied all portions of the NTS and DMV. In the RWIS rats, more than 10% of OTR-IR and V_1bR-IR neurons were activated in the DMV, while lower ratio in the NTS.

Conclusion

RWIS activates both oxytocinergic and vasopressinergic neurons in the PVN and SON, which may project to the NTS or DMV mediating the activity of the neurons by OTR and V_1bR.