侧脑室注射肾上腺髓质素增加大鼠心血管相关核团中c-fos的表达并激活脑内一氧化氮神经元

本研究利用Fos蛋白和一氧化氮合酶(nNOS)双重免疫组化方法,观察侧腑脑室注射肾上腺髓质素(adrenomedullin,ADM)对大鼠心血管相关核中c-fos表达及一氧化氮神经元的影响,以探讨ADM在中枢的作用部位并研究其在中枢的作用是否有NO神经元参与。侧脑室注射ADM(1nmol／kg,3nmol／kg)诱发脑干的孤束核、最后区、蓝斑核、臂旁核和外侧巨细胞旁核,下丘脑的室旁核、视上核才腹内侧核以及前脑的中央杏仁核和外侧缰核等多个部位的心血管中枢出现大量Fos样免疫反应神经元。侧脑室注射ADM(3nmol／kg),引起脑干的孤束核、外侧巨细胞旁核,下丘脑的室旁核、视上核内的Fos-nNOS双标神经元增加;ADM(1nmol／kg)亦可引起室旁核、视上核内的Fos-nNOS双标神经元增加,而对孤束核、外侧巨细胞旁核内的Fos-nNOS双标神经元无影响。降钙素基因相关肽(calcitonin gene—related peptide,CGRP)受体拈抗剂CGRP8-37(30nmol／kg)可明显减弱此效应。以上结果表明,ADM可兴奋脑内多个心血管相关核闭的神经元并激活室旁核、视上核、孤束核及外侧巨细胞核内一氧化氮神经元,此效应可能部分山CGRP受体介导。     

Evidence that NPY Y1 receptors are involved in stimulation of feeding by orexins (hypocretins) in sated rats

Neuropeptide Y (NPY) produced in the arcuate nucleus (ARC) of the hypothalamus stimulates feeding both directly by activating NPY receptors and indirectly through release of the orexigenic peptides, galanin and beta-endorphin (beta-END), in the paraventricular nucleus (PVN) and surrounding neural sites. Orexin A and orexin B, produced outside the ARC in the lateral hypothalamic area (LH), have recently been shown to stimulate feeding. In the present studies we tested the hypothesis that NPYergic signaling may mediate feeding stimulated by orexins. In adult male rats injected intracerebroventricularly (i.c.v.) with orexin A (3, 10, 15 nmol) or orexin B (3, 10, 30 nmol) feeding was stimulated in a dose-dependent manner; maximal feeding was seen after 15 nmol orexin A and 30 nmol orexin B. To determine whether NPY may mediate this orexin stimulated feeding, we used 1229U91, a selective NPY Y1 receptor antagonist (NPY-A). Whereas NPY-A on its own was ineffective, it suppressed NPY-induced feeding. Furthermore, NPY-A completely blocked the feeding evoked by either orexin A (15 nmol) or orexin B (30 nmol). These results show that orexin A and B stimulate feeding and further suggest that these excitatory effects may be mediated by NPYergic signaling through Y1 receptors. These findings are in accord with the view that the orexin-NPY pathway may comprise a functional link upstream from NPY within the hypothalamic appetite regulating network.     

Actions of neuropeptide W in paraventricular hypothalamus: implications for the control of stress hormone secretion

Neuropeptide W (NPW) is produced in neurons located in hypothalamus and brain stem, and its receptors are present in the hypothalamus, in particular in the paraventricular nucleus (PVN). Intracerebroventricular (ICV) administration of NPW activated, in a dose-related fashion, the hypothalamic-pituitary-adrenal axis, as determined by plasma corticosterone levels in conscious rats but, at those same doses, did not stimulate the release of oxytocin or vasopressin into the peripheral circulation or alter blood pressure or heart rate. The ability of ICV-administered NPW to stimulate the hypothalamic-pituitary-adrenal axis in conscious male rats was blocked by intravenous pretreatment with a corticotropin-releasing hormone antagonist. This suggested an action of NPW in the parvocellular division of the PVN. Indeed, in hypothalamic slice preparations (whole cell patch recording), bath application of NPW depolarized and increased the spike frequency of the majority of electrophysiologically identified putative neuroendocrine PVN neurons. Effects on membrane potential were maintained in the presence of TTX, suggesting them to be direct postsynaptic actions on these neuroendocrine cells. Our data suggest that endogenous NPW, produced in brain, may play a physiologically relevant role in the neuroendocrine response to stress.     

Possible inhibitory role of prolactin-releasing peptide for ACTH release associated with running stress

Exercise around the lactate threshold induces a stress response, defined as "running stress." We have previously demonstrated that running stress is associated with activation of certain regions of the brain, e.g., the paraventricular hypothalamic nucleus (PVN) and supraoptic nucleus, that are hypothesized to play an integral role in regulating stress-related responses, including ACTH release during running. Thus we investigated the role of prolactin-releasing peptide (PrRP), found in the ventrolateral medulla and the nucleus of the solitary tract, which is known to project to the PVN during running-induced ACTH release. Accumulation of c-Fos in PrRP neurons correlated with running speeds, reaching maximal levels under running stress. Intracerebroventricular injection of neutralizing anti-PrRP antibodies led to increased plasma ACTH level and blood lactate accumulation during running stress, but not during restraint stress. Exogenous intracerebroventricular administration of low doses of PrRP had the opposite effects. Therefore, our results suggest that, during running stress, PrRP-containing neurons are activated in an exercise intensity-dependent manner, and likewise the produced endogenous PrRP attenuates ACTH release and blood lactate accumulation during running stress. Here we provide a novel perspective on understanding of PrRP in the endocrine-metabolic response associated with running stress.     

Orexin depolarizes rat hypothalamic paraventricular nucleus neurons

Orexins, also called hypocretins, are newly discovered hypothalamic peptides that are thought to be involved in various physiological functions. In spite of the fact that orexin receptors, especially orexin receptor 2, are abundant in the hypothalamic paraventricular nucleus (PVN), the effects of orexins on PVN neurons remain unknown. Using a whole cell patch-clamp recording technique, we investigated the effects of orexin-B on PVN neurons of rat brain slices. Bath application of orexin-B (0.01-1.0 microM) depolarized 80.8% of type 1 (n = 26) and 79.2% of type 2 neurons tested (n = 24) in the PVN in a concentration-dependent manner. The effects of orexin-B persisted in the presence of TTX (1 microM), indicating that these depolarizing effects were generated postsynaptically. Addition of Cd(2+) (1 mM) to artificial cerebrospinal fluid containing TTX (1 microM) significantly reduced the depolarizing effect in type 2 neurons. These results suggest that orexin-B has excitatory effects on the PVN neurons mediated via a depolarization of the membrane potential.     

Diminished feeding responsiveness to orexin A (hypocretin 1) in aged rats is accompanied by decreased neuronal activation

Orexin A is produced in caudal lateral, posterior, perifornical, and dorsomedial hypothalamic areas. Orexin A in the rostro-dorsal lateral hypothalamic area (rLHa) stimulates feeding and activates several feeding-regulatory brain areas. We hypothesized that aging diminishes feeding and c-Fos-immunoreactivity (c-Fos-ir; marker of neuronal activation) response to orexin A. Young (3 mo), middle-aged (12 mo), and old (24 mo) male Fischer 344 rLHa-cannulated rats were injected with orexin A (0.5, 1, and 2 nmol). Food intake was measured at 1, 2, and 4 h. c-Fos-ir in hypothalamic, limbic, and hindbrain regions was measured in two additional sets of rLHa-orexin A injected rats. In a separate study, orexin A effects on feeding and c-Fos-ir were measured in 6-mo-old rats. Orexin A significantly elevated feeding in rats aged 3, 6, and 12 mo in the 0-1 and 1-2- h time intervals, whereas in old rats this was significant in the 1-2 h time interval only. At 1 h, 6-8 (of 14) brain areas showed elevated c-Fos-ir in response to orexin A in 3- and 6-mo-old rats, but 24-mo-old rats exhibited attenuated or absent c-Fos-ir response in all brain regions except the hypothalamic paraventricular nucleus (PVN) and rostral nucleus of the solitary tract (rNTS). Orexin A did not elevate c-Fos-ir in 3-mo-old rats at 2 h after injection, whereas the PVN and mediodorsal thalamic nucleus (MD) showed elevated c-Fos-ir at 2 h in 24-mo-old rats. These data suggest that delayed and diminished feeding responses in old animals may be due to ineffective neural signaling and implicate the orexin A network as one feeding system affected by aging.     

Angiotensin depolarizes parvocellular neurons in paraventricular nucleus through modulation of putative nonselective cationic and potassium conductances

Neurosecretory parvocellular neurons in the hypothalamic paraventricular nucleus (PVN) exercise considerable influence over the adenohypophysis and thus play a critical role in neuroendocrine regulation. ANG II has been demonstrated to act as a neurotransmitter in PVN, exerting significant impact on neuronal excitability and also influencing corticotrophin-releasing hormone secretion from the median eminence and, therefore, release of ACTH from the pituitary. We have used whole cell patch-clamp techniques in hypothalamic slices to examine the effects of ANG II on the excitability of neurosecretory parvocellular neurons. ANG II application resulted in a dose-dependent depolarization of neurosecretory neurons, a response that was maintained in tetrodotoxin (TTX), suggesting a direct mechanism of action. The depolarizing actions of this peptide were abolished by losartan, demonstrating these effects are AT(1) receptor mediated. Voltage-clamp analysis using slow voltage ramps revealed that ANG II activates a voltage-independent conductance with a reversal potential of -37.8 +/- 3.8 mV, suggesting ANG II effects on a nonselective cationic current. Further, a sustained potassium current characteristic of I(K) was significantly reduced (29.1 +/- 4.7%) by ANG II. These studies identify multiple postsynaptic modulatory sites through which ANG II can influence the excitability of neurosecretory parvocellular PVN neurons and, as a consequence of such actions, control hormonal secretion from the anterior pituitary.     

Orexin A (hypocretin 1) injected into hypothalamic paraventricular nucleus and spontaneous physical activity in rats

In humans, nonexercise activity thermogenesis (NEAT) increases with positive energy balance. The mediator of the interaction between positive energy balance and physical activity is unknown. In this study, we address the hypothesis that orexin A acts in the hypothalamic paraventricular nucleus (PVN) to increase nonfeeding-associated physical activity. PVN-cannulated rats were injected with either orexin A or vehicle during the light and dark cycle. Spontaneous physical activity (SPA) was measured using arrays of infrared activity sensors and night vision videotaped recording (VTR). O(2) consumption and CO(2) production were measured by indirect calorimetry. Feeding behavior was assessed by VTR. Regardless of the time point of injection, orexin A (1 nmol) was associated with dramatic increases in SPA for 2 h after injection (orexin A: 6.27 +/- 1.95 x 10(3) beam break count, n = 24; vehicle: 1.85 +/- 1.13 x 10(3), n = 38). This increase in SPA was accompanied by compatible increase in O(2) consumption. Duration of feeding was increased only when orexin A was injected in the early light phase and accounted for only 3.5 +/- 2.5% of the increased physical activity. In a dose-response experiment, increases in SPA were correlated with dose of orexin A linearly up to 2 nmol. PVN injections of orexin receptor antagonist SB-334867 were associated with decreases in SPA and attenuated the effects of PVN-injected orexin A. Thus orexin A can act in PVN to increase nonfeeding-associated physical activity, suggesting that this neuropeptide might be a mediator of NEAT.     

Myricetin Facilitates Potassium Currents and Inhibits Neuronal Activity of PVN Neurons

The effects of myricetin on hypothalamic paraventricular nucleus (PVN) neurons in rats were investigated. By whole-cell patch clamp detection in hypothalamic brain slices, we showed that the action potential frequency in type-I PVN neurons dose-dependently decreased after myricetin treatment. Further studies demonstrated that myricetin may enhance potassium currents and shifts the voltage-dependence of activation of potassium currents to more negative potentials by 6.07 mV. Using calcium free/cadmium perfusion solution could reverse myricetin-induced enhancement of potassium currents in PVN neurons. These results suggested that inhibition of hypothalamic PVN neurons by myricetin might be attributed to the enhancement of potassium currents.     

Hypothalamic paraventricular injections of ghrelin: effect on feeding and c-Fos immunoreactivity

The paraventricular hypothalamic nucleus (PVN) appears to integrate orexigenic properties of a novel peptide, ghrelin. Thus, we examined central mechanisms underlying feeding generated by intra-PVN ghrelin. We established that 0.03 nmol of PVN-injected ghrelin was the lowest dose increasing food consumption and it induced c-Fos immunoreactivity (a marker of neuronal activation) in the PVN itself, as well as in other feeding-related brain areas, including the hypothalamic arcuate and dorsomedial nuclei, central nucleus of the amygdala, and nucleus of the solitary tract. We conclude that the PVN, as part of larger central circuitry, mediates orexigenic properties of ghrelin.     

Neuropeptide FF and neuropeptide VF inhibit GABAergic neurotransmission in parvocellular neurons of the rat hypothalamic paraventricular nucleus

Neuropeptide FF (NPFF) and neuropeptide VF (NPVF) are octapeptides belonging to the RFamide family of peptides that have been implicated in a wide variety of physiological functions in the brain, including central autonomic and neuroendocrine regulation. The effects of these peptides are mediated via NPFF1 and NPFF2 receptors that are abundantly expressed in the rat brain, including the hypothalamic paraventricular nucleus (PVN), an autonomic nucleus critical for the secretion of neurohormones and the regulation of sympathetic outflow. In this study, we examined, using whole cell patch-clamp recordings in the brain slice, the effects of NPFF and NPVF on inhibitory GABAergic synaptic input to parvocellular PVN neurons. Under voltage-clamp conditions, NPFF and NPVF reversibly and in a concentration-dependent manner reduced the evoked bicuculline-sensitive inhibitory postsynaptic currents (IPSCs) in parvocellular PVN neurons by 25 and 31%, respectively. RF9, a potent and selective NPFF receptor antagonist, blocked NPFF-induced reduction of IPSCs. Recordings of miniature IPSCs in these neurons following NPFF and NPVF applications showed a reduction in frequency but not amplitude, indicating a presynaptic locus of action for these peptides. Under current-clamp conditions, NPVF and NPFF caused depolarization (6-9 mV) of neurons that persisted in the presence of TTX but was abolished in the presence of bicuculline. Collectively, these data provide evidence for a disinhibitory role of NPFF and NPVF in the hypothalamic PVN via an attenuation of GABAergic inhibitory input to parvocellular neurons of this nucleus and explain the central autonomic effects of NPFF.     

Adrenalectomy enhances endotoxemia-induced hypophagia: higher activation of corticotrophin-releasing-factor and proopiomelanocortin hypothalamic neurons

Inflammatory and infectious processes evoke neuroendocrine and behavioral changes known as acute-phase response that includes activation of the hypothalamo-pituitary-adrenal (HPA) axis and reduction of food intake. Besides its action as the most important ACTH secretagogue, corticotrophin-releasing factor (CRF), synthesized in the paraventricular nucleus (PVN), is also involved in the control of food intake. Alpha-melanocyte stimulating hormone (α-MSH) in the arcuate nucleus also plays a role in the energy homeostasis, possessing anorexigenic effects. To investigate the participation of neuropeptides involved in the regulation of food intake during endotoxemia, we administrated lipopolysaccharide (LPS) in sham-operated and adrenalectomized (ADX) male Wistar rats to evaluate food intake, hormone responses and Fos-CRF and Fos-α-MSH immunoreactivity in the PVN and arcuate nucleus, as well as CRF and POMC mRNA expression in these hypothalamic nuclei. In sham-operated rats, treatment with LPS (100 µg/kg) showed lower food intake, higher plasma ACTH and corticosterone levels, as well as an increase in Fos-CRF double labeled neurons and CRF mRNA expression in the PVN, with no changes in Fos-α-MSH immunoreactivity and POMC mRNA expression in the arcuate nucleus, compared to saline treated rats. After LPS treatment, ADX rats showed further increase in plasma ACTH levels, marked decrease of food intake, higher Fos-CRF immunoreactive neurons in the PVN and CRF mRNA expression, as well as an increase in Fos-α-MSH immunoreactivity and POMC mRNA expression in the arcuate nucleus, compared to sham-operated rats treated with LPS. In conclusion, the present data indicate that the marked hypophagia during endotoxemia following ADX is associated with an increased activation of CRF and POMC neurons in the hypothalamus and an increased mRNA expression of these neuropeptides.     

A short note on oxytocin and stress attenuation

Stress is integral part of life and it initiates appropriate response at times of adversities to promise survival. Stress could be either physiological or psychogenic. Stress is often psychogenic in nature and it induces the release of cortisol from adrenal cortex into circulation by activating Hypo thalamo-pituitary-adrenal axis (HPA). Cortisol thus released mediates the stress response by its catabolic effects to enhance the activity of vital organs during emergency. However, prolonged activation of the HPA axis can lead to physical and mental illness as an outcome of persistent stress. Nature has bestowed the biological system with an array of endogenous mechanisms to buffer stress. Oxytocin, a nano-peptide released by the magno-cellular neurons of hypothalamic paraventricular nucleus (PVN) is an efficient stress buffering neuro-peptide. This hormone mediates many physiological and behavioural functions get released during stress. It attenuates the stress axis initiated by the release of corticotropin releasing hormone (CRH) from the parvocellular neurons of the same hypothalamic nucleus. Oxytocin released by PVN exerts an inhibitory effect on the release of CRH by down-regulating the expression of the gene that transcribes for this hypothalamic hormone. Thus, it inhibits the release of adreno cotico trophic hormone (ACTH) and cortisol, exerting an overall suppressive modulation of the stress axis and attenuates stress.     

Oxytocin actions within the supraoptic and paraventricular nuclei: differential effects on peripheral and intranuclear vasopressin release

In response to forced swimming (FS), AVP is released somato-dendritically within the supraoptic nucleus (SON) and paraventricular nucleus (PVN), but not from neurohypophyseal terminals into blood. Together with AVP, oxytocin (OXT) is released within the SON and PVN. Here, we studied the role of intra-SON and intra-PVN OXT in the regulation of local AVP release and into the blood in male rats. Within the SON, bilateral retrodialysis of an OXT receptor antagonist (OXT-A) increased local AVP release in response to FS [60 s, 21 degrees C, vehicle twofold, not significant (ns); OXT-A: 15-fold increase, P < 0.05] without significantly affecting basal AVP release. In addition, local OXT-A elevated plasma AVP secretion under basal conditions (twofold increase, P < 0.05) without further elevation after FS. Within the PVN, exposure to FS elevated local AVP release, reaching significance only in the OXT-A group (vehicle: 1.4-fold, ns; OXT-A: 1.6-fold increase, P = 0.050). Bilateral OXT-A into the PVN did not affect peripheral AVP secretion either under basal or stress conditions. Basal ACTH concentrations tended to be elevated by local OXT-A within the PVN (1.7-fold increase, P = 0.076). In contrast, the swim-induced ACTH secretion was attenuated after retrodialysis of OXT-A within both the SON (at 5 min) and PVN (at 15 min) (P < 0.05 both) compared with vehicle. The results demonstrate a receptor-mediated effect of OXT within the SON and PVN on local and neurohypophyseal AVP release, which depends upon the activity conditions. Further, while exerting an inhibitory effect on hypothalamo-pituitary-adrenal axis activity under basal conditions, hypothalamic OXT is essential for an adequate acute ACTH response.     

Hypocretin/orexin type 1 receptor in brain: role in cardiovascular control and the neuroendocrine response to immobilization stress

Hypocretin/orexin acts pharmacologically in the hypothalamus to stimulate stress hormone secretion at least in part by an action in the hypothalamic paraventricular nucleus, where the peptide's receptors have been localized. In addition, orexin acts in the brain to increase sympathetic tone and, therefore, mean arterial pressure and heart rate. We provide evidence for the role of endogenously produced hypocretin/orexin in the physiological response to immobilization stress and identify the receptor subtype responsible for this action of the peptide. Antagonism of the orexin type 1 receptor (OX(1)R) in the brain prevented the ACTH-stimulating effect of centrally administered hypocretin/orexin. Furthermore, pretreatment of animals with the OX(1)R antagonist blocked the ACTH response to immobilization/restraint stress. The OX(1)R antagonist did not, however, block the pharmacological or physiological release of prolactin in these two models. Antagonism of the OX(1)R also blocked the central action of orexin to elevate mean arterial pressures and heart rates in conscious rats. These data suggest receptor subtype-selective responses to hypocretin/orexin and provide further evidence for the importance of endogenously produced peptide in the physiological control of stress hormone secretion.     

Gastrin-releasing peptide mediated regulation of 5-HT neuronal activity in the hypothalamic paraventricular nucleus under basal and restraint stress conditions

The purpose of this study was to examine the gastrin-releasing peptide (GRP) mediated regulation of 5-HT neuronal activity in the paraventricular nucleus of the hypothalamus under basal and restraint stress conditions. Intracerebroventricular (icv) administration of GRP (1, 10, 100 ng/rat) increased 5-HIAA concentrations in the paraventricular nucleus (PVN) of the hypothalamus, but was without effect in the accumbens, suprachiasmatic and arcuate nuclei. Administration of (Leu(13)-psi-CH(2)NH-Leu(14)) Bombesin (10, 100 and 1000 ng/rat; icv), a GRP antagonist, had no effect by itself on PVN serotonergic activity; however, a dose of 1 microg/rat of this compound, completely blocked the increase of 5-HIAA concentrations induced by GRP (10 ng). Restraint stress increased serotonergic activity -as shown by an elevation of 5-HIAA in the PVN- as well as plasma ACTH and corticosterone. This stress-induced activation of both the serotonergic neurons and the hypothalamus-pituitary-adrenal axis was blocked by CRF and GRP antagonists. Interestingly, when the activation of hypothalamic 5-HT neurons was induced by GRP administration, alpha-helical (9-41) CRF was ineffective.These data suggest that GRP, by acting on GRP receptors but not via CRF receptors, increases 5-HT neuronal activity in the PVN. In turn, it appears that endogenous GRP and CRF receptor ligands are both simultaneously involved in the regulation of the increase in 5-HT neuronal activity, ACTH and corticosterone secretion, under stress conditions.     

Neuropeptide-Y and ACTH-immunoreactive innervation of corticotropin releasing factor (CRF)-synthesizing neurons in the hypothalamus of the rat. An immunocytochemical analysis at the light and electron microscopic levels

Corticotropin releasing factor (CRF), synthesized in neurons of the hypothalamic paraventricular nucleus (PVN), is one of the main regulators of the pituitary-adrenal cortex endocrine axis. In order to elucidate the possible involvement of the central neuropeptide-Y (NPY)- and adrenocorticotroph hormone (ACTH)-immunoreactive (IR) systems in the innervation of hypophysiotrophic CRF-synthesizing neurons, immunocytochemical double labelling studies were conducted in the hypothalamus of the rat to localize CRF-synthesizing neurons, as well as neuronal fibers exhibiting NPY and ACTH-immunoreactivity, respectively. The parvocellular subnuclei of the PVN received an intense NPY- and ACTH-IR innervation. At the light microscopic level, these peptidergic axons were associated with the dendrites and perikarya of CRF-IR neurons. Ultrastructural analysis revealed that NPY- and ACTH-IR axons established synaptic specializations with parvocellular neurons expressing CRF-immunoreactivity. These findings indicate that both neuropeptide-Y and adrenocorticotroph hormone containing neuronal systems of the brain are capable of influencing adrenal function via synaptic interactions with hypophysiotrophic CRF-synthesizing neurons. The data also support the concept that NPY and ACTH might be utilized as neuromodulators within the PVN.     

Plasticity of neuroendocrine transducers under the combined influence of the radiation and light exposure

The structural changes of neurons of the rat hypothalamic supraoptic (SON) and of paraventricular (PVN) nucleus after 48 h of bright light exposure, of 5 Gy whole-body X-irradiation and of their combination subjected to the analysis by means of light-optic and of electron microscopy for the estimation of radimodificated effect of light exposure lasted 24 h a day and plasticity of neuroendocrine transducers interacted with the optic sensory system. The structural changes of neurons of the SON after combined action are less considerable and more prolonged in comparison with the PVN that loas defermined by their direct connection with the optic sensory system via the retinohypothalamic tract.     

Anatomical evidence for interaction of ACTH1-39 immunostained fibers and hypothalamic paraventricular neurons that project to the dorsal vagal complex

Anatomical evidence is presented for an interaction of ACTH1-39 immunostained fibers and a specific population of hypothalamic paraventricular (PVN) neurons; these neurons project to the dorsal vagal complex (DVC) of brainstem medulla. Bilateral injection of 10% HRP-WGA into DVC is incorporated into nerve terminals and transported retrogradely to cell bodies in the parvocellular subdivision of PVN, as revealed by standard HRP-WGA histochemistry or antibody to wheatgerm agglutinin followed by immunocytochemical techniques. Labeled cells are localized predominantly in the ventral portion of the caudal medial parvocellular subdivision and ventrolaterally in the posterior subnucleus of PVN. Few labeled cells are seen in the anterior parvocellular PVN, rostrally in the medial parvocellular component and in the dorsal cap. HRP-WGA cells are rarely observed in the magnocellular divisions of PVN. Dual-staining immunocytochemical-retrograde tracing techniques in the same tissue section demonstrate ACTH1-39 fibers in intimate anatomical proximity to parvocellular PVN neurons that project to DVC. It is suggested that this interaction may partially account for the known cardiovascular effects of opiocortins and supports the role of the paraventricular nucleus in hypothalamic integration and modulation of cardiovascular control.