ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00491.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA stereotaxic surgical method was developed for interrupting the nerve fibres running through the rat pituitary stalk to the posterior pituitary gland without obliterating the hypothalamo‐pituitary portal circulation. The pituitary stalk was compressed by the blunt tip of an L‐shaped rotating knife. Successful operations produced mild diabetes insipidus, disappearance of arginine vasopressin from the neural lobe, accumulation of arginine vasopressin and neurosecretory material in the pituitary stalk and no infarction in the anterior lobe of the pituitary gland. In female rats, the oestrous cycle was only temporarily disturbed. Plasma prolactin and corticosterone levels were high during the first 24 h after the stalk compression but returned to normal baseline levels from the second day after the operation. One week after the operation plasma adrenocorticotropin and prolactin levels were in the control range while plasma a‐melanocyte‐stimulating hormone was elevated. Denervation of the posterior pituitary gland may help in studying the neural control of intermediate lobe function and the role of the neural lobe in various endocrine conditions, and may serve as a model for lesions of the pituitary stalk and formation of ectopic neurohypophysis in th

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00492.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractTo test the hypothesis that synaptic inputs to the paraventricular nucleus mediate stress‐induced increases in corticotropin‐releasing peptide expression in the paraventricular nucleus of the hypothalamus (PVH), relative levels of the mRNAs encodingv corticotropin‐releasing factor (CRF) and arginine vasopressin (AVP) were followed,in situ, in animals subjected to chronic footshock stress and concurrent local administration of tetrodotoxin or vehicle. Consistent with previous findings, a 7‐day exposure to chronic footshock resulted in a 2.1‐fold increase in CRF mRNA levels in the parvocellular division of the PVH. The footshock paradigm also resulted in at least a 41% increase in AVP transcripts in this same region; this effect was localized predominantly to CRF‐immunoreactive neurons. The Stressor did not significantly alter AVP mRNA levels in the magnocellular division of the PVH. Tetrodotoxin, administered to the PVH via osmotic minipump, blocked the stress‐induced rise in CRF and AVP mRNAs, but had no significant effect on basal levels of these transcripts. The results support the view that maintenance of the enhanced central drive on pituitary‐adrenal activity seen in response to chronic stress is mediated via neural in

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00493.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe compartmental interrelationships of the metabolically related amino‐acids glutamate, GABA and glutamine and the metabolically unrelated amino‐acids taurine and glycine in the rodent pituitary, were investigated by light microscopic immunocytochemistry using highly specific antisera. Glutamate‐like immunoreactivity was abundant in astrocytes in the posterior pituitary. Glutamine immunoreactivity was present only at low levels in the posterior pituitary, but was abundant in astrocytes within the intermediate lobe. Other glia‐like ceils in the anterior pituitary were also glutamine‐immunoreactive. GABA immunoreactivity was abundant in the intermediate lobe but absent from anterior and posterior lobes. The GABA immunoreactivity mainly took the form of small punctata, the majority of which were in intimate apposition to the glutamine‐immunoreactive glia. Strong taurine immunoreactivity was present in astrocytes in the posterior pituitary but only weak labelling was present in intermediate and anterior lobes of the pituitary. Specific glycine immunoreactivity was not detected in the pituitary. These results suggest that glutamate‐immunoreactive astrocytes in the posterior pituitary, unlike glia in loci such as the retina, do not convert much, if any, of their glutamate content into glutamine (or if they do, it is rapidly further metabolized to another compound), whereas those astrocytes in the intermediate lobe do contain glutamine. The spatial association of GABAergic fibres with glutamine‐positive astrocytes raises the possibility that astrocytes in the intermediate lobe receive a GABAergic innervation. Glutamate, glutamine and taurine (or their metabolites) may have roles as neuroactive substances regulating pitu

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00494.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractExpression of β‐tubulin mRNA was examined in androgen‐sensitive motoneurons of the spinal nucleus of the bulbocavernosus (SNB) in adult male rats by in situ hybridization histochemistry using cDNA encoding mouse β‐tubulin. Hybridizable β‐tubulin mRNA was localized in the somata and proximal dendrites of SNB motoneurons. Removal of androgen by castration significantly reduced the expression level of β‐tubulin mRNA in the SNB motoneurons, whereas the change was prevented by testosterone treatment. On the contrary, castration or testosterone treatment did not induce any changes in the expression level of β‐tubulin mRNA in the androgen‐insensitive motoneurons of the retrodorsolateral nucleus. These results suggest that androgen regulates the expression of β‐tubulin gene in the SNB motoneurons and may provide evidence for the molecular mechanisms of hormonally‐induced neuronal plasticity

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00495.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractEffects of novel environmental stimuli on vasopressin and oxytocin secretion by the pituitary were studied in dehydrated male rats. As the novel environmental stimuli, rats were transferred to an experimental room, placed in a box painted black and given a pure tone auditory stimulus of 2 kHz. Exposure of rats to the novel environmental stimuli for a period of 2 min decreased plasma concentrations of vasopressin and increased plasma levels of adrenocorticotrophic hormone (ACTH) and prolactin, but did not significantly change the plasma level of oxytocin. The stimuli, however, became ineffective for producing the suppressive vasopressin response as the period of exposure was prolonged to more than 5 and up to 30 min, although the prolonged stimuli were still effective for inducing facilitatory ACTH and prolactin responses. After repeated exposures of rats to the environmental stimuli once a day for 5 or 10 days, the stimuli became disabled from producing the suppressive vasopressin response. However, the rats were still capable of responding to the novel stimuli of another kind. All these data suggest that novelty stress suppresses vasopressin secretion but does not change oxytocin secretion. In order to test the possibility that glucocorticoids expectedly secreted by the adrenals in response to the stress might have suppressed vasopressin secretion, a large amount of dexamethasone was administered to the rat before testing. Dexamethasone pretreatment depressed plasma levels of ACTH and vasopressin as reported previously and blocked the facilitatory ACTH response to the novelty stress. However, dexamethasone treatment did not affect the suppressive vasopressin response to the novelty stress. Thus, it is likely that the suppressive vasopressin response to novelty stress does not primarily depend upon endogenous glucocorticoids.

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00496.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn rats, opioidergic β‐endorphin (βEP1–31) is produced and released from neurons of arcuate nuclei in the hypothalamus. Although the neuropeptide has been implicated in sexual maturation and stress‐induced reproductive dysfunction, the intra‐hypothalamic regulation of βEP neurons remains unclear. Employing long‐term monolayer cultures of neonatal rat hypothalamic cells, we report here that 4 days of treatment with 10 μM forskolin increased approximately 3‐fold (P<0.01) the proportion of immunoreactive (ir)‐ βEP positive neurons bearing neurites. In addition, treatment of forskolin also enhanced ir‐βEP release (634 ± 59 pg/well; mean β SE, n = 4, P<0.01) by 14‐fold and ir‐βEP content (119±13 pg/well; P<0.01) by 2‐fold above that of vehicle‐treated cultures; in both instances, the EC50and the Emax, of forskolin were approximately 10μM and 100 μM, respectively. The forskolin‐stimulated release of ir‐βEP was mimicked by cholera toxin and (Bu)2cAMP treatment in a dose‐related manner, but not by pertussis toxin. Although by itself 3‐isobutyl‐1‐methyl‐xanthine (100μM) only doubled ir‐βEP secretion, it markedly potentiated the stimulatory effect of forskolin. This forskolin‐induced stimulation was reversible and in cultures re‐exposed to the same drug within the first 24 h period, there was a marked increase in the stimulated release of ir‐βEP (P<0.05); re‐challenge of forskolin at later stages, however, induced a smaller but significant secretion of ir‐βEP (P<0.01) compared to that of vehicle‐treated control cultures. Sephadex G‐50 gel Chromatographie profile of the media prepared from forskolin‐treated cultures revealed a major ir‐βEP peak of 3 K M. Highperformance liquid chromatography analysis showed that ir‐βEP of the 3 K M, species was eluted with a retention time similar to that of synthetic rat βEP1–31.We thus conclude that the adenylyl cyclase‐cAMP system plays an important role in the modulation of βEP1–31production and release from hypothalamic βEP neurons in culture. Furthermore, the functional responsiveness and the orphological development of these neurons are af

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00497.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractNeuropeptide Y (NPY) is a 36 amino‐acid peptide. It is localized within the brain but is also present peripherally. It is a well substantiated orexigenic peptide with several other endocrine and behavioural effects. In this study NPY mRNA levels were measured, using the polymerase chain reaction amplification technique, in the hypothalamus of pre‐obese (unweaned 13‐day‐ old), young (weaned 28‐day‐old) and adult (11‐week‐old) obesefa/farats and compared to those of lean age‐matched controls. Before weaning, pre‐obese pups had the same NPY mRNA levels as controls. After weaning NPY mRNA levels were increased 2‐fold in young 28‐day‐old and 4‐fold in adult obese rats, relative to corresponding controls. When adult obese rats were intracerebroventricularly‐treated with ovine corticotropin‐releasing hormone (oCRF) for 7 days, they stopped gaining body weight elative to vehicle‐infused obese controls. Upon measuring NPY mRNA levels in the hypothalamus of these two groups of animals, it was shown that the high NPY mRNA levels of vehicle‐treated (control) obese rats were decreased by 3‐fold following the intracerebroventricular oCRF administration. It is proposed that: 1) hypothalamic NPY may play a role in the establishment and maintenance of the genetic obesity syndrome of thefa/farat, and 2) hypothalamic NPY cou

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00498.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractNeural input to the hypothalamic luteinizing hormone‐releasing hormone (LHRH) neurons was investigated in male starlings (Sturnus vulgaris) using electron microscopy combined with immunocytochemistry. Birds (4 to 6 in each group) were sampled at four stages of a photoperiodically induced reproductive cycle: (a) sexually immature but photosensitive, under short days; (b) during sexual maturation after 7 to 25 long days; (c) during gonadal regression after 35 to 50 long days; and (d) when fully photorefractory after 11 months exposure to long days. The length of the perikaryal membrane, the number and length of axo‐somatic terminals in contact with it and the number and length of synaptic modifications within the terminals were measured for a minimum of six LHRH neurons in each brain. The number of axo‐somatic terminals per neuron and the number per unit length of perikaryal membrane did not differ in birds of groups (a), (b) and (c), but was significantly greater (P<0.05) in the fully refractory birds (group d). Similarly, the number of synaptic modifications was significantly greater (P<0.05) in group (d) than in the other groups. These results are consistent with increased neural input to the LHRH perikarya in photorefractory birds after prolonged exposure to long days, although there was no indication of a change in input at the time of gonadal regre

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00499.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractVaginal‐cervical stimulation (VCS), provided by mating or manual probing, induces many reproductive behavioral and endocrine changes in female rats. These changes include an increase in lordosis duration, heat termination and pseudopregnancy. Electro‐physiological and [14C]2‐deoxy‐D‐glucose studies collectively show that neurons in the medial preoptic area, ventromedial hypothalamus and midbrain central gray respond to manual VCS. In the present study we immunocytochemically labeled brain sections for Fos, the protein product of the immediate early gene c‐fos, to detect VCS‐responsive neurons in hormone‐primed animals receiving VCS by mating or manual probing. In Experiment 1, females receiving mounts and intromissions were compared to: 1) vaginally‐masked females receiving mounts but no VCS, 2) females exposed to an intact anesthetized male or 3) females not exposed to males or the testing arena. Those animals receiving VCS showed a dramatic increase in the number of Fos‐immunoreactive cells in the medial preoptic area, posterodorsal portion of the medial amygdala and bed nucleus of the stria terminalis, as well as the dorsomedial hypothalamus, ventromedial hypothalamus and midbrain central gray. These effects of VCS were confirmed in Experiment 2 in animals receiving manual vaginal‐cervical probing. These findings extend previous electrophysiological and [14C]2‐deoxy‐D‐glucose studies by providing evidence that additional brain areas respond to VCS by mating

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1993.tb00500.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY