摘要:

Conventional light and confocal microscopy of thick vibratome sections of the hypothalamus of adult male and female rats immunostained for the astrocytic marker glial fibrillary acidic protein (GFAP) revealed that the supraoptic nucleus (SON) contains two morphologically distinct types of astrocytes. One has a stellate form, similar to that of most astrocytes in the adult CMS. The other has a morphology reminiscent of radial glia in the developing CNS: from their cell bodies, located along the ventral glia lamina (VGL), arise one long thick process that spans the SON in the coronal plane, several horizontally‐oriented processes that form a dense network in the VGL, and a short process oriented towards the pia. The latter astrocytes are immunoreactive for vimentin, an intermediate filament protein of immature glial cells and a marker for radial glia. The stellate astrocytes showed no vimentin immunoreactivity. The functional significance of each type of supraoptic astrocyte is at present unknown but the presence of radial glia‐like cells in this hypothalamic region suggests that the SON retains a certain degree of immaturity during adulthood, that may be linked to its well known capacity to undergo neuronal‐glial plasticity under physiological and experimental stimul

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00357.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The neuropeptide oxytocin has long been known as a potent contractor of the uterus. However, it has remained difficult to attribute a definite role for neurohypophysial oxytocin in either the initiation or continuation of labour (1). Most recently, Lefebvre and colleagues (2) have suggested that oxytocin produced in the uterus, rather than in the hypothalamus, may be more important in parturition since at term the uterus of the rat contains 70‐fold more mRNA for oxytocin than the hypothalamus, and this disappears at about the time of parturition. Despite the high levels of mRNA the uterus contains only nanogram quantities of immunoreactive oxytocin per gram wet weight at term (2), compared to microgram quantities present in the pituitary (3,4). Here we show that activation of the neurohypophysial oxytocin system occurs, as reflected by expression of immunoreactivity for Fos in the hypothalamic supraoptic nucleus, and that this activation is indeed critical for normal parturition, since its inhibition results in a significant prolongation of parturition. In addition, we present evidence that pulsatile delivery of oxytocin into the circulation is important for the efficient progress of parturition, indicating that a major role of the neuronal circuits regulating oxytocin secretion for parturition, as is already known for suckling, is to produce an appropriately patterned hormonal output for efficient biological actio

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00358.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn vivomicrodialysis and retrodialysis were used to investigate the role of oxytocin (OXY) release in the mediobasal hypothalamus (MBH) of the ewe in the control of sexual receptivity. Initial experiments showed that OXY release was significantly increased in ovariectomized animals treated with progesterone and oestradiol when they were sexually receptive towards males and received intromissions. No such increases were seen during tests where the ewes were receptive but the males were prevented from achieving intromission. By contrast, OXY release was significantly reduced in tests where the ewes were not receptive to the male. In a second experiment artificial vaginocervical stimulation (VCS) was found to significantly increase OXY release when the animals were treated with oestradiol and this effect was potentiated by progesterone priming. OXY release in the MBH was not significantly altered by VCS in the presence of progesterone priming alone. Plasma OXY concentrations were significantly increased by VCS following all three hormone treatments but no one treatment was significantly more effective than another. Noradrenaline release in the MBH was only significantly increased following VCS when progesterone priming was given before oestradiol treatment. No effects of VCS on release of GABA, glutamate or dopamine were seen but their basal concentrations were significantly increased by the combined steroid treatment compared to oestradiol alone. In a third experiment it was found that OXY (10 μM) infused bilaterally into the MBH of receptive ewes, by retrodialysis, significantly decreased sexual receptivity and increased the release of noradrenaline and GABA. Finally, in a fourth experiment is was shown that multiple intromissions significantly reduced sexual receptivity.These results show that OXY release in the MBH is increased by natural or artificial VCS and that this is modulated by sex steroids. The inhibitory action of OXY infusions into the MBH on sexual receptivity suggests that a functional role of this peptide within this brain region might be to mediate decreases in sexual receptivity which we observed following multiple intromissions. It is probable that the behavioural effects of this peptide are primarily mediated directly rather than through a modulation of noradrenaline and GABA release

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00359.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractArginine vasopressin (AVP) has been shown to have a unique sensitization effect whereby repeated injection of AVP into a lateral cerebral ventricle or a mediobasal region of the rat forebrain below the lateral septum and including the anterior hypothalamus referred to as the ventral septal area, causes enhanced motor responses to the ligand. To elucidate possible neuronal mechanisms responsible for AVP sensitization, 1) we determined the dose and the time required for the development and expression of AVP sensitization, and 2) we tested the hypotheses that AVP sensitization may result in a) alteration of septal AVP V1 receptor affinity or number, and/or b) alteration of septal AVP V1 receptor signal transduction (phosphatidylinositol hydrolysis) mechanisms. Our behavioral data show that the magnitude of AVP sensitization varies with dose and time, and the effect is dependent on the time interval between injections, in that an initial intracerebroventricular AVP injection enhances the sensitivity of the animals to the motor effects of similar AVP injections given 6 h to 6 days later but not to injections given hourly or weekly. No changes in septal AVP binding site density and affinity, as measured by [3H]AVP binding to septal synaptic plasma membrane, were found in sensitized animals; [3H]inositol monophosphate stimulation in response to AVP in septal slices, however, was found to be significantly enhanced. This enhanced [3>H]inositol monophosphate stimulation appears specific to a V1‐type receptor because it was significantly reduced in the presence of the V1 receptor antagonist, d(CH2)5Tyr(Me)AVP, and was not found using oxytocin or the V2 receptor agonist, DDAVP. Our results therefore indicate that receptor binding, while critical to peptide neurotransmitter action, is not the sole factor for determining responsiveness. Rather, an appropriate schedule of AVP administration, which may cause changes in postreceptor effector system(s) such as inositol phosphate hydrolysis, appears most importan

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00360.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe recent observation that the central oxytocin (OT) receptor has high affinity for both OT and arginine vasopressin (AVP) raises the possibility that it may be involved in some of the central actions of AVP. Repeated intracerebroventricular (icv) injections of AVP in rats evoke an unusual sensitization phenomenon in that a first exposure to the peptide enhances the sensitivity (sensitization) of the brain to a second exposure. This report investigates the possibility that the OT receptor may be involved in the mediation of the phenomenon of sensitization, using OT, a specific OT receptor agonist, [Thr4, Gly7]OT, and a specific OT receptor antagonist, d(CH2)5, [Tyr(Me)2, Thr4, Tyr‐NH29]OVT (compound 6; cpd 6), as well as a V1 AVP receptor antagonist, d(CH2)5Tyr(Me)AVP. Peptides were injected icv in conscious, adult male Sprague‐Dawley rats. The data showed that: 1) a first icv AVP injection (10 pmol/5μl) enhanced the sensitivity of the rat brain to the motor response of a second AVP injection (10 pmol/5 μl) given 24 h later; 2) injection of d(CH2)5Tyr(Me)AVP (100 pmol/5 μl icv) but not cpd 6, (100 pmol/5 μl icv) 2 min prior to the first AVP injection, blocked AVP‐induced sensitization; 3) a first injection of OT or [Thr4, Gly7]OT (10 pmol/5 μl) enhanced the sensitivity of the brain to the motor actions of a subsequent AVP injection given 24 h later; 4) the magnitude of this cross‐sensitization induced by OT pretreatment varied with dose and appeared to be ten times more potent than the sensitization induced by a first AVP injection; 5) injection of cpd 6 (100 pmol/5 μl) but not d(CH2)5Tyr(Me)AVP (100 pmol/5 μl icv) 2 min prior to the first OT injection (1 pmol/5 μl) blocked the cross‐sensitization induced by OT; 6) an injection of OT (100 to 1,000 pmol/5 μl) or [Thr4, Gly7]OT (10 pmol/5 μl) in rats that had been cross‐sensitized with OT or [Thr4, Gly7]OT pretreatment did not evoke enhanced motor responses; 7) OT injected 2 min prior to the second AVP injection in AVP‐sensitized rats did not block the enhanced AVP‐induced motor responses; 8) AVP‐induced [3H]inositol monophosphate accumulation in septal slices was also enhanced in rats cross‐sensitized by OT pretreatment.These results suggest that while pre‐exposure of the rat brain to both AVP and OT alters the responsiveness of the rat brain to subsequent AVP exposures, AVP sensitization appears to be mediated via the V1 AVP receptor, whereas cross‐sensitization by OT may be mediated via the OT receptor. The ability of OT to alter the responsiveness of the rat brain to subsequent AVP injection suggests a role for this peptide

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00361.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn pubertal, but not prepubertal, monkeys ovariectomy (OVX) results in an elevation of circulating luteinizing hormone (LH) levels. To determine if the castration‐induced LH increase in pubertal monkeys is due to an increase in pulsatile LH‐releasing hormone (LHRH) release, effects of OVX onin vivoLHRH release in the stalk‐median eminence were examined in fully conscious monkeys using a push‐pull perfusion method. The average ages (± SEM) of female rhesus monkeys in each group at OVX were 14.5±0.6 months (n = 6; prepubertal), 25.0±1.3 months (n = 5; early pubertal) and 37.8 ± 2.1 months (n = 6; midpubertal). Perfusate samples from the stalk‐median eminence were obtained in 10‐min fractions for 6 h in the morning (0600 to 1200 h) and 6 h in the evening (1800 to 2400 h), from the same subjects before OVX, and at 29 days and approximately 100 days after OVX. LHRH levels in perfusates were measured by radioimmunoassay. LH levels throughout the experiment were monitored by periodic blood sampling.OVX resulted in a significant LH increase in early and midpubertal monkeys (P>0.001 for both), but not in prepubertal monkeys. Similarly, OVX in early and midpubertal monkeys increased mean LHRH release when examined 29 days after surgery (P>0.05 and P>0.01, respectively). The OVX‐induced LHRH increases in early and midpubertal monkeys remained elevated at approximately 100 days postcastration. Furthermore, it was found that effects of OVX on the increased LHRH release were primarily due to the elevation of basal release and pulse amplitude, but not pulse frequency. In contrast, OVX did not cause any significant effects on pulsatile LHRH release in prepubertal monkeys.The results indicate that an increase in LHRH release and a concomitant increase in circulating LH occurs after OVX in pubertal monkeys, but not in prepubertal monkeys. These data are consistent with the hypothesis that the low level of LH in circulation before the onset of puberty is due to a low amount of LHRH release which is independent of ovarian steroid feedback and that the maturity of the neuronal control system for the pulsatile LHRH release is responsible for the onset of puberty. After the onset of puberty, the negative feedback of ovarian steroid hormones becomes important to the regulation of gon

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00362.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractLipocortin 1 (LC1: also called annexin 1) was first described as a putative second messenger protein for the anti‐inflammatory steroids in peripheral tissues. In the present study,in vitroandin vivomethods were used to examine its potential role within the hypothalamus as a mediator of the regulatory actions of the glucocorticoids on the hypothalamo‐pituitary‐adrenocortical axis of the rat.In thein vitrostudies, the effects of human recombinant LC1 (hu‐r‐LC1) on the concomitant release of the two major corticotrophin‐releasing factors (CRF‐41 and arginine vasopressin, AVP) from isolated hypothalami removed from chronically adrenalectomized rats were compared with those of dexamethasone in the presence and absence of appropriate secretagogues, namely phospholipase A2(PLA2), interleukin‐6 (IL‐6) and a non‐specific depolarizing agent, K+(56 mM). The spontaneous release of CRF‐41in vitrowas unaffected by either hu‐r‐LC1 (5 to 100 ng/ml) or dexamethasone (1 μM). Both compounds however reduced the release of the neuropeptide evoked by IL‐6 (5 ng/ml) but failed to modify the secretory responses to PLA2(25 U/ml) or K+(56 mM). Dexamethasone (1 μM) had no effect on the basal release of AVP but effectively blocked the secretion of the peptide induced by either IL‐6 (10 ng/ml) or PLA2(25 U/ml). In complete contrast, hu‐r‐LC1 (5 to 100 ng/ml) stimulated the release of AVP and potentiated the secretory responses to IL‐6 (10 ng/ml) and PLA2(25 U/ml) but not to K+(56 mM). The hypothalamic responses to PLA2stimulation (25 U/ml) were associated with significant (P<0.01) increases in prostaglandin E2release which, in some instances, were potentiated by hu‐r‐LC1 (5 to 20 ng/ml).In vivo, administration of histamine (0.6 mg/100 g body wt, ip) produced significant (P<0.01) increases in the serum corticosterone concentration and in the hypothalamic LC1 content. Neither hu‐r‐LC1 (0.6 to 1.2 μg) nor a polyclonal anti‐LC1 antibody (3 μl, diluted 1:200), injected intracerebroventricularly (icv), influenced either the resting serum corticosterone concentration or the hypersecretion of the steroid evoked by histamine stress. A lower dose of the recombinant protein (0.3 μg icv) also failed to alter basal corticosterone release but, in contrast to the higher doses, potentiated the pituitary‐adrenocortical responses to histamine.The results suggest that LC1 may contribute to some aspects of peptide release in the hypothalamus but that its actions are not

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00363.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractUsing immunocytochemical techniques, cells containing estrogen and progestin receptors have been observed in many discrete regions of the guinea‐pig forebrain, including the mediobasal hypothalamus and preoptic area. While most reaction product is located within cell nuclei, we have reported abundant reaction product in perikaryal cytoplasm and neuronal processes as well. Ultrastructural analysis has revealed the presence of estrogen and progestin receptors in atypical subcellular sites within the hypothalamus, including dendrites and axon terminals. In order to determine if microtubule‐dependent intracellular transport is involved in intraneuronal transport of steroid hormone receptors, ovariectomized guinea‐pigs were injected intracerebroventricularly with the microtubule inhibitor, colchicine, and brain sections at the level of the hypothalamus were immunostained for estrogen receptors. This treatment resulted in the appearance of estrogen receptor immunoreactivity in the paraventricular and mediodorsal thalamic region, areas typically devoid of estrogen receptor‐immunoreactive cells in guinea‐pigs. In a second study on progestin receptors, we observed the colchicine‐induced accumulation of progestin receptor immunoreactivity in the paraventricular thalamic, mediodorsal thalamic and lateral dorsal thalamic areas as well as in the medial amygdala, all areas typically devoid of progestin receptor immunoreactivity. While estradiol injection induced progestin receptor immunoreactivity in the hypothalamus and preoptic area as described previously, it had no effect on the colchicine‐induced accumulation in the thalamus and amygdala. These results provide evidence that in some neurons, progestin receptors and estrogen receptors are transported intracellularly, apparently at a rapid enough rate that they do not ordinarily accumulate within t

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00364.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe aim of this study was to characterize further the transmitter content and the location of the parent cells of tyrosine hydroxylase‐immunoreactive boutons terminating on luteinizing hormone‐releasing hormone‐ and glutamic acid decarboxylase‐immunoreactive neurons in the rat medial preoptic area. Electron microscopic immunostaining for luteinizing hormone‐releasing hormone, tyrosine hydroxylase or glutamic acid decarboxylase was performed on desipramine‐pretreated (to protect norepinephrine and epinephrine axons) rats which received a stereotaxic injection of 6‐hydroxydopamine into the medial preoptic area anteroventral periventricular nucleus 48 h prior to sacrifice. This treatment induced acute degeneration of dopamine axon terminals characterized by the development of autophagous cytolysosomes, an early morphological sign of catecholamine axon degeneration. To further define the cells of origin of these dopamine boutons, the anterograde markerPhaseolus vulgarisleucoagglutinin was iontophoretically applied to the zona incerta. Six days later, rats received a 6‐hydroxydopamine injection into the zona incerta or the lateral ventricle, and 48 h later, double immunostaining was performed forPhaseolus vulgarisleucoagglutinin and tyrosine hydroxylase, luteinizing hormone‐releasing hormone, or glutamic acid decarboxylase on preoptic area vibratome sections.Following the 6‐hydroxydopamine injection into the anteroventral periventricular nucleus, autophagous cytolysosome‐containing degenerated axons were found in synaptic contact with both luteinizing hormone‐releasing hormone and GABA neurons in the medial preoptic area, confirming that these are dopaminergic connections. Following the double injection treatment, 6‐hydroxydop‐amine‐induced degenerated,Phaseolus vulgarisleucoagglutinin‐labeled dopamine axons originating in the zona incerta were not found to contact luteinizing hormone‐releasing hormone‐containing or GABA cells. Instead, many degenerated,Phaseolus vulgarisleucoagglutinin‐immunopositive boutons were observed in the dorsomedial and paraventricular nuclei of the hypothalamus. These observations indicate that tyrosine hydroxylase‐immunoreactive fibers terminating on the medial preoptic area luteinizing hormone‐releasing hormone and GABA cells are dopaminergic and most probably originate from dopamine neurons located in anterior

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00365.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effects of steroid hormones on sexual dimorphisms in the brain, behavior and accessory sex structures were investigated in two species of whiptail lizards. The studies were conducted both in adults and hatchlings of a sexually reproducing species (Cnemidophorus inornatus) and an all‐female species (C. uniparens) which displays ‘sexual’ behaviors typical of males and females. Adults were gonadectomized and approximately 3 months later given either a Silastic capsule filled with sex steroid or an empty capsule. Young animals of both species were left intact and given a capsule on the day of hatching. An additional group ofC. uniparenswas ovariectomized on the day of hatching. Following treatment, measures of oviduct (estrogen‐dependent), renal sex segment (androgen‐dependent) and wolffian duct (androgen‐dependent) hypertrophy were taken in some experiments. Animals were also tested for sexual behavior in some of the studies. The volumes of the anterior hypothalamus‐preoptic area and ventromedial hypothalamus were measured in each individual. Estrogen, testosterone and dihydrotestosterone stimulated peripheral structures at both time periods in both sexes and species. The hormones also stimulated courtship and copulatory behaviors in many of the adult animals. However, testosterone in the anterior hypothalamus‐preoptic area of maleC. inornatuswas the only treatment which produced parallel effects on the volume of a brain area and the behaviors which it controls. These data add whiptail lizards to the list of species in which steroid hormones affect the volume of brain regions in adulthood, but suggest that such changes in morphology are not necessarily predictive of functio

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00366.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY