Early experience alters limbic forebrain Fos responses to a stressful interoceptive stimulus in young adult rats

The present study examined whether manipulation of the early life experience of rat pups might alter the later ability of an interoceptive challenge to recruit central neural circuits that receive visceral sensory signals and generate stress responses. For this purpose, litters were exposed to daily maternal separation for either 15 min (MS-15) or 180 min (MS-180) from postnatal days (P)1 to P10. Pups in control litters were raised under standard conditions (i.e., no separations). Similar to previous reports in adult rats, adolescent rats (P35-45) with a developmental history of MS-15 displayed less anxiety-like behavior on the elevated plus maze compared to control and MS-180 rats. As young adults (P50-60), rats were anesthetized and perfused with fixative 90 min after viscerosensory stimulation via lithium chloride (LiCl, 0.15 M, 1% BW, i.p.) or saline control. In all three rearing groups, Fos activation within brainstem and forebrain regions of interest was significantly enhanced after LiCl vs. saline. MS-15 rats tended to display fewer LiCl-activated neurons in most brain regions compared with rats in the other two rearing groups. This trend reached significance within the dorsal bed nucleus of the stria terminalis. The ability of MS-15 to alter limbic forebrain activation in rats after an interoceptive challenge may contribute to the effect of early life experience to modulate physiological and behavioral stress responses more generally.     

Exercise training normalizes an increased neuronal excitability of NTS-projecting neurons of the hypothalamic paraventricular nucleus in hypertensive rats

Elevated sympathetic outflow and altered autonomic reflexes, including impaired baroreflex function, are common findings observed in hypertensive disorders. Although a growing body of evidence supports a contribution of preautonomic neurons in the hypothalamic paraventricular nucleus (PVN) to altered autonomic control during hypertension, the precise underlying mechanisms remain unknown. Here, we aimed to determine whether the intrinsic excitability and repetitive firing properties of preautonomic PVN neurons that innervate the nucleus tractus solitarii (PVN-NTS neurons) were altered in spontaneously hypertensive rats (SHR). Moreover, given that exercise training is known to improve and/or correct autonomic deficits in hypertensive conditions, we evaluated whether exercise is an efficient behavioral approach to correct altered neuronal excitability in hypertensive rats. Patch-clamp recordings were obtained from retrogradely labeled PVN-NTS neurons in hypothalamic slices obtained from sedentary (S) and trained (T) Wistar-Kyoto (WKY) and SHR rats. Our results indicate an increased excitability of PVN-NTS neurons in SHR-S rats, reflected by an enhanced input-output function in response to depolarizing stimuli, a hyperpolarizing shift in Na(+) spike threshold, and smaller hyperpolarizing afterpotentials. Importantly, we found exercise training in SHR rats to restore all these parameters back to those levels observed in WKY-S rats. In several cases, exercise evoked opposing effects in WKY-S rats compared with SHR-S rats, suggesting that exercise effects on PVN-NTS neurons are state dependent. Taken together, our results suggest that elevated preautonomic PVN-NTS neuronal excitability may contribute to altered autonomic control in SHR rats and that exercise training efficiently corrects these abnormalities.     

Central circuits regulating the sympathetic outflow to lumbar muscles in spinally transected mice by retrograde transsynaptic transport

Despite considerable interest in the mechanisms that control the hyperalgesia associated with muscle inflammation, the CNS descending pathways that coordinate autonomic circuits regulating lumbar muscles are not adequately understood. Here we used both pseudorabies virus (PRV)-614 retrograde transsynaptic tracing and spinally transected method in 33 C57BL/6J mice to map the polysynaptic pathways between lumbar muscle and CNS. Tissues were processed for dual-label immunocytochemical detection between PRV-614 and tryptophan hydroxylase (TPH) or tyrosine hydroxylase (TH)-expressing neurons in CNS. In intact mice, PRV-614 was transported to the intermediolateral column (IML) and ventral horn (VH) of spinal cord, with subsequent transport to many brain regions, including the medullary raphe nuclei, rostral ventrolateral medulla (RVLM), A5 cell group regions (A5), locus coeruleus (LC), the medullary and pontine reticular formation nucleus (MRN and PRN), paraventricular nucleus of the hypothalamus (PVN), and other central sites. However, PRV-614 in spinally transected mice produced retrograde infection of IML, with subsequent transport to main brain regions that have been shown to contribute to regulating sympathetic circuits, including RVLM, Lateral paragigantocellular reticular nucleus (LPGi), A5, LC, and PVN, whereas PRV-614 labeling in VH and MRN was eliminated in almost every case. In above five brain regions, dual-labeling immunocytochemistry showed coexpression of PRV-614/TPH and PRV-614/TH immunoreactive (IR) neurons involved in these regulatory circuits. Our results reveal a hierarchical organization of central autonomic circuits controlling the lumbar muscles, thus providing neuroanatomical substrates for the central catecholaminergic and serotonergic system to regulate the lumbar muscles.     

Intermittent activation of peripheral chemoreceptors in awake rats induces Fos expression in rostral ventrolateral medulla-projecting neurons in the paraventricular nucleus of the hypothalamus

Despite the well-established sympathoexcitation evoked by chemoreflex activation, the specific sub-regions of the CNS underlying such sympathetic responses remain to be fully characterized. In the present study we examined the effects of intermittent chemoreflex activation in awake rats on Fos-immunoreactivity (Fos-ir) in various subnuclei of the paraventricular nucleus of the hypothalamus (PVN), as well as in identified neurosecretory preautonomic PVN neurons. In response to intermittent chemoreflex activation, a significant increase in the number of Fos-ir cells was found in autonomic-related PVN subnuclei, including the posterior parvocellular, ventromedial parvocellular and dorsal-cap, but not in the neurosecretory magnocellular-containing lateral magnocellular subnucleus. No changes in Fos-ir following chemoreflex activation were observed in the anterior PVN subnucleus. Experiments combining Fos immunohistochemistry and neuronal tract tracing techniques showed a significant increase in Fos-ir in rostral ventrolateral medulla (RVLM)-projecting (PVN-RVLM), but not in nucleus of solitarii tract (NTS)-projecting PVN neurons. In summary, our results support the involvement of the PVN in the central neuronal circuitry activated in response to chemoreflex activation, and indicate that PVN-RVLM neurons constitute a neuronal substrate contributing to the sympathoexcitatory component of the chemoreflex.     

Acute nicotine activates c-fos and activity-regulated cytoskeletal associated protein mRNA expression in limbic brain areas involved in the central stress-response in rat pups during a period of hypo-responsiveness to stress

In adult rats, acute nicotine, the major psychoactive ingredient in tobacco smoke, stimulates the hypothalamic-pituitary-adrenal axis (HPA), resulting in activation of brain areas involved in stress and anxiety-linked behavior. However, in rat pups the first two postnatal weeks are characterized by hypo-responsiveness to stress, also called the 'stress non-responsive period' (SNRP). Therefore, we wanted to address the question if acute nicotine stimulates areas involved in the stress response during SNRP. To determine neuronal activation, the expression of the immediate-early genes c-fos and activity-regulated cytoskeletal associated protein (Arc) was studied in the central nucleus of the amygdala (CeA), bed nucleus stria terminalis (BST) and paraventricular hypothalamic nucleus (PVN), which are areas involved in the neuroendocrine and central stress response. Rat pups received nicotine tartrate (2 mg/kg) or saline by i.p. injection at postnatal days (P) 5, 7 and 10 and their brains were removed after 30 min. We used semi-quantitative radioactive in situ hybridization with gene specific antisense cRNA probes in coronal sections. In control pups, c-fos expression was low in most brain regions, but robust Arc hybridization was found in several areas including cingulate cortex, hippocampus and caudate. Acute nicotine resulted in significant induction of c-fos expression in the PVN and CeA at P5, P7 and P10, and in the BST at P7 and P10. Acute nicotine significantly induced expression of Arc in CeA at P5, P7 and P10, and in the BST at P10. In conclusion, acute nicotine age dependently activated different brain areas of the HPA axis during the SNRP. After P7, the response was more pronounced and included the BST, suggesting differential maturation of the HPA axis in response to nicotine.     

Early life experience alters behavior during social defeat: focus on serotonergic systems

Early life experience can have prolonged effects on neuroendocrine, autonomic, and behavioral responses to stress. The objective of this study was to investigate the effects of early life experience on behavior during social defeat, as well as on associated functional cellular responses in serotonergic and non-serotonergic neurons within the dorsal raphe nucleus, a structure which plays an important role in modulation of stress-related physiology and behavior. Male Long Evans rat pups were exposed to either normal animal facility rearing or 15 min or 180 min of maternal separation from postnatal days 2-14. As adults, these rats were exposed to a social defeat protocol. Differences in behavior were seen among the early life treatment groups during social defeat; rats exposed to 180 min of maternal separation from postnatal days 2-14 displayed more passive-submissive behaviors and less proactive coping behaviors. Analysis of the distribution of tryptophan hydroxylase and c-Fos-like immunoreactivity in control rats exposed to a novel cage and rats exposed to social defeat revealed that, independent of the early life experience, rats exposed to social defeat showed an increase in the number of c-Fos-like immunoreactive nuclei in serotonergic neurons in the middle and caudal parts of the dorsal dorsal raphe nucleus and caudal part of the ventral dorsal raphe nucleus, regions known to contain serotonergic neurons projecting to central autonomic and emotional motor control systems. This is the first study to show that the dorsomedial part of the mid-rostrocaudal dorsal raphe nucleus is engaged by a naturalistic stressor and supports the hypothesis that early life experience alters behavioral coping strategies during social conflict; furthermore, this study is consistent with the hypothesis that topographically organized subpopulations of serotonergic neurons principally within the mid-rostrocaudal and caudal part of the dorsal dorsal raphe nucleus modulate stress-related physiological and behavioral responses.     

c-Fos expression in the supraoptic nucleus is the most intense during different durations of restraint water-immersion stress in the rat

Restraint water-immersion stress (RWIS) can induce anxiety, hypothermia, and severe vagally-mediated gastric dysfunction. The present work explored the effects of different durations of RWIS on neuronal activities of the forebrain by c-Fos expression in conscious rats exposed to RWIS for 0, 30, 60, 120, or 180 min. The peak of c-Fos induction was distinct for different forebrain regions. The most intense c-Fos induction was always observed in the supraoptic nucleus (SON), and then in the hypothalamic paraventricular nucleus (PVN), posterior cortical amygdaloid nucleus (PCoA), central amygdaloid nucleus (CeA), and medial prefrontal cortex (mPFC). Moreover, body temperature was reduced to the lowest degree after 60 min of RWIS, and the gastric lesions tended to gradually worsen with the prolonging of RWIS duration. These data strongly suggest that these nuclei participate in the organismal response to RWIS to different degrees, and may be involved in the hypothermia and gastric lesions induced by RWIS.     

大鼠视交叉上核与室旁核的联系──病毒跨神经元顺行追踪研究

本实验采用假狂犬病毒（猪疱疹病毒）作为跨神经元追踪示踪物，对下丘脑视交叉上核与下丘脑室旁核的联系进行了研究．实验大鼠于摘除双侧颈上交感神经节后，向单侧眼球内注入假狂犬病毒，术后动物分别存活48、56、72及96h．结果显示：56h组仅在视交叉上核内有极少数的细胞被病毒感染；72h组机交叉上核内被病毒标记的细胞增多，定劳核内也出现了被病毒感染的神经元，主要集中在背内侧帽区；96h组在室旁核内被病毒感染的神经元增加，除背内侧帽区外，其它亚孩也出现了被病毒感染的神经元；各实验组的亚室旁带未见有被病毒标记的神经元．以上表明视交叉上核的传出纤维直接投射到室旁核，两核团神经无间可能存在有直接的突触联系．     

Identification of neuroanatomic circuits from spinal cord to stomach in mouse: retrograde transneuronal viral tracing study

To determine the spinal innervation and neuronal connections is important for studying gastric carbohydrate metabolism and motor responses. Neurons involved in the efferent control of the stomach were identified following visualization of pseudorabies virus (PRV)-614 retrograde tracing. PRV-614 was injected into the ventral stomach wall in 13 adult C57BL/6J strain male mice. On the fifth day postinjection, animals were humanely sacrificed, and spinal cords were removed and sectioned, and processed for PRV visualization. The virus injected into the ventral stomach wall was specifically transported to the thoracic spinal cord. At 5 d after injection of the PRV-614, stomach enlargement and tissue edema were found, and PRV-614 positive cells were found in the intermediolateral cell column, the intercalates nucleus or the central autonomic nucleus of spinal cord segments T3 to L1, and major PRV-614 labeled cells were focused in the T6-10 segment. Our results revealed neuroanatomical circuits between stomach and the spinal intermediolateral cell column neurons.     

Prenatal stress produces sex differences in nest odor preference

Prenatal stress (PS) and early postnatal environment may alter maternal care. Infant rats learn to identify their mother through the association between maternal care and familiar odors. Female Wistar rats were exposed to restraint stress for 30 min, 4 sessions per day, in the last 7 days of pregnancy. At birth, pups were cross-fostered and assigned to the following groups: prenatal non-stressed mothers raising non-stressed pups (NS:NS), prenatal stressed mothers raising non-stressed pups (S:NS), prenatal non-stressed mothers raising stressed pups (NS:S), prenatal stressed mothers raising stressed pups (S:S). Maternal behaviors were assessed during 6 postpartum days. On postnatal day (PND) 7, the behavior of male and female pups was analyzed in the odor preference test; and noradrenaline (NA) activity in olfactory bulb (OB) was measured. The results showed that restraint stress increased plasma levels of corticosterone on gestational day 15. After parturition, PS reduced maternal care, decreasing licking the pups and increasing frequency outside the nest. Female pups from the NS:S, S:NS, S:S groups and male pups from the S:S group showed no nest odor preference. Thus, at day 7, female pups that were submitted to perinatal interventions showed more impairment in the nest odor preference test than male pups. No changes were detected in the NA activity in the OB. In conclusion, repeated restraint stress during the last week of gestation reduces maternal care and reduces preference for a familiar odor in rat pups in a sex-specific manner.     

Effects of intracerebroventricular administration of neuropeptide W30 on neurons in the hypothalamic paraventricular nucleus in the conscious rat

We demonstrated that intracerebroventricular (i.c.v.) administration of NPW30 increases the arterial blood pressure (ABP), heart rate (HR), and plasma catecholamine concentrations in conscious rats. NPW has been reported to be an important stress mediator in the central nervous system that modulates the hypothalamus-pituitary-adrenal (HPA) axis and sympathetic outflow. To examine the effects of NPW30 on the neural activity of the hypothalamic paraventricular nucleus (PVN), which is an integrative center of the autonomic and endocrine functions relevant to stress responses, we simultaneously recorded the single-unit activity in the PVN, ABP, and HR in conscious freely moving rats. Of the non-phasic (irregular) PVN neurons (n=35) examined, NPW30 (i.c.v. 3 nmol) elicited excitation in 22 neurons, inhibition in 7 neurons, and no response in 6 neurons, accompanied with increases in ABP and HR, whereas low-dose NPW30 (i.c.v. 0.3 nmol) did not affect the unit activity, ABP, or HR. Neurons that were affected by NPW30 were then further examined for their responses to perturbation in ABP and systemic administration of cholecystokinin-8 (CCK). The majority of neurons also showed responses to CCK, phenylephrine (PE), or nitroprusside (SNP). Our data suggest that central NPW30 modulates PVN neuronal activities, which might be involved in the regulation of cardiovascular function and energy balance through the autonomic nervous system, particularly, under stress-related conditions.     

“Green odor” inhalation by rats down-regulates stress-induced increases in Fos expression in stress-related forebrain regions

In the present study, on rats, a quantitative analysis of Fos protein immunohistochemistry was performed as a way of investigating the effects of inhalation of green odor (a mixture of equal amounts of trans-2-hexenal and cis-3-hexenol) on the neuronal activations in stress-related forebrain regions induced by acute and repeated stress. Rats were exposed to restraint stress for 90 min each day for 1, 2, 4, 7, or 11 consecutive days. The hypothalamic paraventricular nucleus (PVN), amygdala, hippocampus and paraventricular thalamic nucleus (PVT) were examined. Both acute and repeated restraint stress increased Fos-positive cells in the entire hypothalamic PVN, in the central and medial amygdala, and in PVT, although these responses declined upon repeated exposure to such stress. The stress-induced Fos responses were much weaker in rats that inhaled green odor during each day's restraint. No increases in Fos-positive cells were observed in the hippocampus in acutely stressed rats. The Fos-immunoreactive response to acute stress shown by the piriform cortex did not differ significantly between the vehicle + stress and green + stress groups. Green odor had inhibitory effects on the stress-induced corticosterone response, body-weight loss, and adrenal hypertrophy. These results suggest that in rats, green odor inhalation may, in an as yet unknown way, act on the brain to suppress activity in the neuronal networks involved in stress-related responses (such as activation of the hypothalamo–pituitary–adrenocortical axis and activation of the sympathetic nervous system, as well as stress-induced fear responses).     

Central stress-integrative circuits: forebrain glutamatergic and GABAergic projections to the dorsomedial hypothalamus,medial preoptic area,and bed nucleus of the stria terminalis

Central regulation of hypothalamo-pituitary-adrenocortical (HPA) axis stress responses is mediated by a relatively circumscribed group of projections to the paraventricular hypothalamus (PVN). The dorsomedial hypothalamus (DMH), medial preoptic area (mPOA), and bed nucleus of the stria terminalis (BST) provide direct, predominantly inhibitory, innervation of the PVN. These PVN-projecting neurons are controlled by descending information from limbic forebrain structures, including the prefrontal cortex, amygdala, hippocampus, and septum. The neurochemical phenotype of limbic circuits targeting PVN relays has not been systematically analyzed. The current study combined retrograde tracing and immunohistochemistry/in situ hybridization to identify the specific sites of glutamatergic and GABAergic inputs to the DMH, mPOA, and BST. Following Fluoro-gold (FG) injections in the DMH, retrogradely labeled cells co-localized with vesicular glutamate transporter mRNA in the prefrontal cortex, ventral hippocampus, and paraventricular thalamus. Co-localization of FG and glutamic acid decarboxylase mRNA was present throughout the central and medial amygdaloid nuclei and septal area. In addition, the mPOA received predominantly GABAergic input from the septum, amygdala, and BST. The BST received glutamatergic projections from the hippocampus and basomedial amygdala, whereas, GABAergic inputs arose from central and medial amygdaloid nuclei. Thus, discrete sets of neurons in the hypothalamus and BST are positioned to summate limbic inputs into PVN regulation and may play a role in HPA dysfunction and stress-related illness.     

Mesolimbic dopaminergic activity responding to acute stress is blunted in adolescent rats that experienced neonatal maternal separation

Neonatal maternal separation (MS), stressful experience early in life, leads to the development of depression-like behaviors in the offspring later in life. This study was conducted to define the neural basis of depression-like behaviors observed in our MS model. Sprague–Dawley pups were separated from dam for 3 h daily during the first 2 weeks of birth (MS) or left undisturbed (NH). All pups were sacrificed on postnatal day 41 with/without 1 h of restraint stress. Restraint stress significantly increased c-Fos expression in the nucleus accumbens (NAcb) of NH pups, but not in MS. In NH pups, restraint stress increased dopamine levels not only in the NAcb but also in the midbrain dopamine neurons; however, these increases were not observed in MS. Gene expression of tyrosine hydroxylase (TH) in the ventral tegmental area (VTA) was increased by acute restraint in NH pups, but not in MS pups. The raphe serotonin level was lower in MS than in NH, and not significantly changed by acute restraint neither in NH nor in MS. Results reveal that experience of neonatal MS may lead to a long-term suppression in the mesolimbic dopamine system of the offspring later in life, in which an epigenetic control may be implicated, such as suppressed gene expression of TH in the midbrain. We conclude that a decreased activity of the mesolimbic dopamine system may play a role in the pathophysiology of depression-like behaviors by neonatal MS, in addition to a decreased serotonin level in the raphe nucleus.     

A subset of presympathetic-premotor neurons within the centrally projecting Edinger–Westphal nucleus expresses urocortin-1

Numerous motivated behaviors require simultaneous activation of somatomotor and autonomic functions. We have previously characterized the organization of brain circuits that may mediate this integration. Presympathetic premotor neurons (PSPMNs) that are part of such circuits are distributed across multiple brain regions, which mediate stress-elicited behavioral and physiological responses, including the Edinger–Westphal nucleus (EW). Based on its connectivity and function, EW has recently been re-classified into a preganglionic (EWpg) and a centrally projecting (EWcp) population. Neurons within EWcp are the major source of urocortin 1 (Ucn-1), an analog of the corticotropin-releasing factor that binds the CRFR1 and CRFR2 receptors and has been implicated in mediating homeostatic responses to stress. We hypothesized that a subset of EWcp PSPMNs expresses Ucn-1. Utilizing dual-label immunofluorescence, we initially mapped the distribution of Ucn-1 and cholinergic neurons within EW in colchicine pre-treated rats. Based on this labeling we divided EWcp into three neuroanatomical levels. To examine connections of EWcp neurons to the gastrocnemius muscle and the adrenal gland, we next employed trans-synaptic tract-tracing in a second group of rats, utilizing two pseudorabies virus (PRV) recombinants that express unique reporter proteins. Using multi-label immunofluorescent staining, we identified the presence of Ucn-1-positive PSPMNs, dually labeled with PRV and present throughout the entire extent of EWcp and intermingled with Ucn-1 neurons infected with one or neither of the viral recombinants. Compared to rats pretreated with colchicine, we observed significantly fewer Ucn-1 neurons in animals that received PRV injections. Post hoc analyses revealed significantly fewer Ucn-1 neurons at the rostral level as compared to the caudal and middle levels. These data suggest functional and anatomic heterogeneity within EWcp; this organization may coordinate various aspects of stress-elicited and emotionally salient behaviors.     

Chronic social stress in the visible burrow system modulates stress-related gene expression in the bed nucleus of the stria terminalis

Prolonged social subjugation produces physiological indices of chronic stress in rats. In the current study, we examined the impact of social stress on glutamic acid decarboxylase (GAD) isoforms, corticotropin-releasing hormone (CRH) and vasopressin mRNA expression in forebrain stress circuitry, using the visible burrow system model of dominance-subordination. Subordinate male rats develop behavioral and neuroendocrine changes consistent with exposure to chronic stress, including marked loss of body weight and elevation of basal plasma corticosterone relative to dominant rats. Forebrain GAD65, GAD67, CRH and vasopressin mRNA expression in central stress-regulatory circuits were examined by in situ hybridization. Elevated CRH mRNA was observed in the oval nucleus of the bed nucleus of the stria terminalis (BST) of subordinate males. In contrast, GAD67 expression was decreased in the interfascicular nucleus of the BST in both the subordinate and dominant rats compared to non-burrow control rats. No changes in CRH, GAD or vasopressin were observed in amygdaloid nuclei, other BST nuclei or in the hypothalamic paraventricular nucleus. Collectively, these data suggest that exposure to the visible burrow system attenuates BST GAD expression regardless of social status, whereas the enhanced physiological responses to social stress seen in subordinates may be associated with enhanced CRH expression in the oval nucleus of the BST.     

Topographic architecture of stress-related pathways targeting the noradrenergic locus coeruleus.

Peripheral sympathetic nerves and brainstem noradrenergic neurons of the locus coeruleus (LC) respond in parallel to a variety of stress-related stimuli which results in norepinephrine release both peripherally and centrally. Elucidation of central pathways subserving modulation of LC neurons point to extranuclear noradrenergic dendrites of LC somata that extend into peri-coerulear areas as a major target of afferents that participate in behavioral and physiological responses to stress. Anterograde tract tracing combined with immunoelectron microscopic detection of the catecholamine synthesizing enzyme tyrosine hydroxylase (TH) has demonstrated that the nucleus of the solitary tract (NTS) and the ventrolateral aspect of the periaqueductal gray (PAG), regions that participate in coordinating autonomic and motor behavior in response to stress, preferentially target the rostral ventromedial aspect of the peri-LC. In contrast, limbic forebrain afferents including the central nucleus of the amygdala (CNA) and the bed nucleus of the stria terminalis (BNST), regions that coordinate emotional responses to external stressors, provide direct synaptic input to noradrenergic dendrites that extend into rostral dorsolateral peri-coerulear areas. Neurochemical identification of transmitter systems impinging on LC indicate that the CNA provides corticotropin-releasing factor (CRF), a peptide essential for integrated physiological responses to stress, to the dorsolateral LC. Endogenous opioid peptides that originate from medullary sources, however, target primarily the "core" of the LC. Our physiological data suggest that stress engages CRF and opioid afferents to the LC, which have opposing influences on this noradrenergic system. The balance between opioid and CRF influences acting in the LC may, in part, maintain the balance of active and passive coping behaviors in response to stress. Understanding the afferent and neurochemical organization of the LC may help elucidate adaptations in neural circuits associated with stress which impact on central noradrenergic function.     

幼鼠中枢神经系统FOS蛋白表达升高与母婴分离相关

 目的 探讨幼鼠中枢神经系统下丘脑室旁核(PVN)及前皮质扣带回(ACC)内FOS蛋白表达与母婴分离(MS)的相关性。方法 按析因设计,32只SD新生大鼠分成4组,每组8只。A1B1组、A1B2组均为MS组,A1B1组在6周龄时接受结直肠扩张刺激(CRD),A1B2组在6周龄时未给予CRD;A2B1组、A2B2组均未给予MS,同为对照组,A2B1组在6周龄时接受CRD,A2B2组在6周龄时未给予CRD。A1B1、A2B1组幼鼠在接受CRD刺激后2 h和A1B2、A2B2组幼鼠一起处死。之后采用SABC免疫组化法检测不同脑区（包括PVN和ACC）内FOS蛋白免疫阳性（FLI）细胞表达情况。结果 新生期MS和幼鼠在6周龄时接受CRD刺激均可使PVN内FLI细胞数显著升高(F分别为7.033、35.212,P＜0.01)。也均使ACC内FLI细胞数显著升高(F分别为22.745、15.106,P＜0.01);两者对FOS蛋白表达的影响无交互作用。结论 幼鼠中枢神经系统（PVN和ACC）FOS蛋白表达升高与新生期MS明显相关。     

Differential neuronal activation in the hypothalamic paraventricular nucleus and autonomic/neuroendocrine responses to I.C.V. endotoxin

The paraventricular nucleus (PVN) of the hypothalamus is a key site for regulating neuroendocrine and autonomic activities. To study the role of the PVN activation in brain inflammation-induced autonomic/endocrine responses, lipopolysaccharide (LPS; 0.5 or 5 microg) was administered i.c.v. and rats were killed 1, 3 or 6 h after the injection. I.c.v. LPS-0.5 microg did not cause changes in mean arterial pressure (MAP) over 6 h, whereas LPS-5 micro induced a temporary decrease in MAP approximately 30 min after the injection. LPS at either dose increased heart rate. Whereas induction of Fos-like immunoreactivity was confined to the dorsal medial parvocellular division (mpd) of the PVN with the lower dose, labeling was found throughout the PVN with the higher dose. At 3 h, LPS-5 microg also stimulated increases in arginine vasopressin (AVP) heteronuclear RNA levels in the posterior magnocellular and dorsal parvocellular divisions of the PVN at 3 h, and activation of catecholaminergic neurons in the hypothalamus and brainstem. Increases in tyrosine hydroxylase (TH) mRNA levels were found in the locus coeruleus at 6 h. LPS at both doses elevated plasma ACTH levels and corticotropin-releasing factor gene expression in the mpd of the PVN. I.c.v. LPS induced IL-1beta mRNA in the meninges and ventricular ependymal lining at 1 h, and in the periventricular PVN at 3 h. Induction of IL-1beta mRNA was found in the lung at 1 h, and a significant increase in plasma LPS binding protein occurred at 3 h.These findings suggest that PVN activation induced by the lower dose of LPS is related primarily to increases in activity of the HPA axis, whereas the higher dose of LPS more widely activates autonomic regulatory centers including the PVN and also stimulates changes in sympathetic output and hypothalamic AVP synthesis. Activation of the PVN by i.c.v. LPS likely occurs through both central and systemic routes. Differential neuronal activation in the PVN is functionally related to autonomic/endocrine responses elicited by brain inflammation.