Journal of Neuroendocrinology
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Insulin and Glucose Administration Stimulates Fos Expression in Neurones of the Paraventricular Nucleus That Project to Autonomic Preganglionic Structures Abstract Insulin and glucose play a key role in the control of body energy homeostasis. However, the anatomical organization of the network of central insulin and glucose sensitive areas is still unclear. In the present study, we used a multiple‐labelling technique combining retrograde tracing and Fos‐like immunohistochemistry, to analyse the anatomical projections from hypothalamic neurones activated by the combined stimulus of insulin and glucose. After intraperitoneal injections of a bolus of insulin plus glucose, Fos‐like immunoreactive neurones were observed in the paraventricular nucleus (PVN), ventromedial and arcuate nuclei, as well as the lateral hypothalamic area. In addition, neurones projecting to the autonomic preganglionic levels in the brainstem and spinal cord potentially involved in the control of glucose metabolism were identified by injections of fluorochrome tracers. Thus, Fluorogold was injected into the intermediolateral cell column of the lower spinal cord and Fast Blue was injected into the dorsal motor nucleus of the vagus. Perikarya of descending neurones were detected chiefly in the dorsal, medial and lateral parvocellular subnuclei and also in the posterior magnocellular subnucleus of the PVN. In contrast, insulin‐glucose activated neurones in the PVN were observed mainly in the medial parvocellular and posterior magnocellular subnuclei. Fluorogold/Fos double‐labelled neurones were only observed in the ventral zone of the medial parvocellular subnucleus. These data indicate that, within the PVN, there could be neurones responding to insulin‐glucose administration, which are involved in the sympathetic control of the classical regulatory structures of body energy homeostasis, such as the liver and pancreas, and which could play a role in the output of the neuronal circuitry controlling food intake.
Journal of Neuroendocrinology - Tập 13 Số 4 - Trang 339-346 - 2001
Progestins’ Rapid Facilitation of Lordosis When Applied to the Ventral Tegmentum Corresponds to Efficacy at Enhancing GABA<sub>A</sub>Receptor Activity Progestins may have actions in the midbrain though γ ‐aminobutyric acid (GABA)A /benzodiazepine receptor complexes (GBRs) that are relevant for sexual receptivity. The efficacy and time course of various progestins to enhance lordosis when applied to the ventral tegmental area (VTA), following progesterone to the ventral medial hypothalamus (VMH) was investigated. Ovariectomized, oestrogen‐primed rats and hamsters with contralateral VMH/VTA cannulae were tested for lordosis before and after implants of P to the VMH and progestins to the VTA. The progestins were P, 5α ‐pregnan‐3,20‐dione (DHP), 5α ‐pregnan‐3α ‐ol‐20‐one(3α ,5α ‐THP), 5α ‐pregnan‐3α ,21‐diol‐20‐one (THDOC), 5β ‐pregnan‐3α ‐ol‐20‐one(3α ,5β ‐THP), 17α ‐ol‐6‐methyl‐4,6‐pregnadiene‐3,20‐dione‐17‐acetate (megestrol acetate, MA), and 6‐chloro‐17‐ol‐4,6‐pregnadiene‐3,20‐dione‐17‐acetate (chlormadinone acetate, CA). Progestins’ effects on GABA‐mediated chloride influx and SR 95531 binding in cortical and midbrain tissue, respectively, were examined in rats and hamsters. 3α ,5α ‐THP and THDOC implants to the VTA were the most effective at immediately facilitating lordosis of rats and hamsters. Two hours later all other progestins, except MA and CA, increased lordosis in rats; only P, 3α ,5α ‐THP, and THDOC were effective in hamsters. The progestins’ effectiveness at facilitating lordosis were similar to their effects on GABA‐stimulated chloride influx and SR 95531 receptor binding (3α ,5α ‐THP and THDOC>P>DHP>3α , 5β ‐THP>MA and CA). These findings suggest that progesterone lordosis enhancing effects in the rodent VTA may be via GBRs.
Journal of Neuroendocrinology - Tập 11 Số 11 - Trang 829-837 - 1999
About Stress Hormones and Resilience to Psychopathology Neuroendocrinology links experience and behaviour to the action of hormones. This review focusses on the corticosteroids, released in hourly pulses and after stress, to illustrate the integration of body, brain and mind achieved by these hormones. Corticosteroids coordinate cell and organ function in concert with other mediators of the stress response over time spans from seconds to hours, days, weeks, or even permanently. The actions exerted by these stress hormones are mediated by two receptor types that control initial stress reactions and manage the later adaptive phases. How the balance between the stress and adaptive responses contributes to resilience and health is a conundrum to be resolved during the next two decades of the existence of the Journal of Neuroendocrinology .
Journal of Neuroendocrinology - Tập 20 Số 6 - Trang 885-892 - 2008
Melatonin: From Seasonal to Circadian Signal Abstract In mammals, the role of melatonin in the control of seasonality is well documented, and the sites and mechanisms of action involved are beginning to be identified. The exact role of the hormone in the circadian timing system remains to be determined. However, exogenous melatonin has been shown to affect the circadian clock. Identification of the molecular and cellular mechanisms involved in this well characterized chronobiotic effect will allow clarification of the role of endogenous melatonin in circadian organization
Journal of Neuroendocrinology - Tập 15 Số 4 - Trang 422-426 - 2003
Endocrine Disrupters: A Review of Some Sources, Effects, and Mechanisms of Actions on Behaviour and Neuroendocrine Systems Some environmental contaminants interact with hormones and may exert adverse consequences as a result of their actions as endocrine disrupting chemicals (EDCs). Exposure in people is typically a result of contamination of the food chain, inhalation of contaminated house dust or occupational exposure. EDCs include pesticides and herbicides (such as dichlorodiphenyl trichloroethane or its metabolites), methoxychlor, biocides, heat stabilisers and chemical catalysts (such as tributyltin), plastic contaminants (e.g. bisphenol A), pharmaceuticals (i.e. diethylstilbestrol; 17α‐ethinylestradiol) or dietary components (such as phytoestrogens). The goal of this review is to address the sources, effects and actions of EDCs, with an emphasis on topics discussed at the International Congress on Steroids and the Nervous System. EDCs may alter reproductively‐relevant or nonreproductive, sexually‐dimorphic behaviours. In addition, EDCs may have significant effects on neurodevelopmental processes, influencing the morphology of sexually‐dimorphic cerebral circuits. Exposure to EDCs is more dangerous if it occurs during specific ‘critical periods’ of life, such as intrauterine, perinatal, juvenile or puberty periods, when organisms are more sensitive to hormonal disruption, compared to other periods. However, exposure to EDCs in adulthood can also alter physiology. Several EDCs are xenoestrogens, which can alter serum lipid concentrations or metabolism enzymes that are necessary for converting cholesterol to steroid hormones. This can ultimately alter the production of oestradiol and/or other steroids. Finally, many EDCs may have actions via (or independent of) classic actions at cognate steroid receptors. EDCs may have effects through numerous other substrates, such as the aryl hydrocarbon receptor, the peroxisome proliferator‐activated receptor and the retinoid X receptor, signal transduction pathways, calcium influx and/or neurotransmitter receptors. Thus, EDCs, from varied sources, may have organisational effects during development and/or activational effects in adulthood that influence sexually‐dimorphic, reproductively‐relevant processes or other functions, by mimicking, antagonising or altering steroidal actions.
Journal of Neuroendocrinology - Tập 24 Số 1 - Trang 144-159 - 2012
Mating‐lnduced FOS‐Like Immunoreactivity in the Rat Forebrain: A Sex Comparison and a Dimorphic Effect of Pelvic Nerve Transection Abstract Previous research has shown that mating induces the expression of the immediate‐early gene, c‐fos , as detected by the increased presence of nuclear FOS‐like immunoreactivity (FOS‐IR), in specific forebrain regions of both male and female rats. In the male both olfactory/vomeronasal (O/V) and genital/somatosensory (G/S) inputs appear to contribute to the neural FOS response to mating whereas in the female G/S input carried by the pelvic nerves appears to mediate the forebrain FOS response. To date, however, no direct sex comparison of the mating‐induced forebrain FOS response has been made in rats maintained under the same steroidal conditions nor has the contribution of afferent sensory input from the pelvic nerves been assessed in males. We first compared the level of FOS‐IR in brain regions of mated and unpaired gonadectomized male and female rats given 5μg/kg estradiol benzoate (EB) for 7 days and 500 μg progesterone (P) 4 h prior to testing. One h after experiencing 1 ejaculation, both sexes showed increased FOS‐IR in the medial preoptic area (MPOA), bed nucleus of the stria terminalis (BNST), medial amygdala, the ventro‐lateral portion of the ventromedial nucleus of the hypothalamus (VMN), and the midbrain central tegmental field (CTF). This increase was significantly greater in the MPOA and medial amygdala of mated females than of males. Bilateral transection of the pelvic nerves significantly attenuated the increase in FOS‐IR after mating in the CTF of male rats and in the MPOA, BNST, VMN, medial amygdala and CTF of females. Thus, following mating there is no sex difference in the brain regions which express c‐fos , but there is a dimorphism in the contribution of afferent information conveyed by the pelvic nerves to the mating‐induced FOS response. The neural FOS response of the female to mating is heavily dependent upon the G/S afferent inputs carried by the pelvic nerves whereas the male's neural c‐fos response may depend on O/V input plus G/S input conveyed via other afferent pathways such as the pudendal nerves.
Journal of Neuroendocrinology - Tập 5 Số 5 - Trang 557-568 - 1993
Evidence that Orexin‐Containing Neurones Provide Direct Input to Gonadotropin‐Releasing Hormone Neurones in the Ovine Hypothalamus Abstract Orexins A and B (ORX) have been added recently to the growing list of neuropeptides implicated in feeding and drinking behaviour as well as neuroendocrine function. In the present study, we have used single and dual labelling immunohistochemistry and a rabbit polyclonal anti‐orexin‐A antibody, which recognizes both ORX A and B, to examine ORX pathways in the sheep hypothalamus. ORX immunoreactive cells were distributed in the dorsomedial hypothalamic nucleus, lateral hypothalamic area, zona incerta and perifornical area; a few cells were also observed in the anterior hypothalamic area. In contrast to distribution in the rat brain, most of the ORX immunoreactive cells are localized to the dorsomedial hypothalamic nucleus and perifornical area; scattered cells are found in lateral hypothalamic area. ORX immunoreactive fibres were widely distributed throughout the hypothalamus and preoptic area with dense innervation of the medial preoptic area and bed nucleus of stria terminalis. Dual labelling demonstrated widespread expression of the long form of the leptin receptor within all ORX cells that were examined. Thirty percent of the gonadotropin releasing hormone (GnRH) cells that were examined had ORX immunoreactive terminals in close contact with no regional or sex differences. FluoroGold injections into the preoptic area retrogradely labelled a subpopulation of ORX cells in the lateral hypothalamic/perifornical area, showing ORX cells of this region project to the preoptic and could potentially provide input to GnRH cells. These findings suggest an integral role for ORX in the regulation of GnRH cells in the sheep and thus provide evidence of a novel mechanism whereby leptin can influence reproductive neuroendocrine function.
Journal of Neuroendocrinology - Tập 13 Số 12 - Trang 1033-1041 - 2001
Hypothalamic‐Pituitary‐Adrenal Function in Chronic Intermittently Cold‐Stressed Neonatally Handled and Non Handled Rats Abstract Neonatally handled (H) animals, as adults, exhibit lower ACTH and corticosterone (B) responses to a number of acute stressors compared to their non‐handled (NH) counterparts. However, little is known about activity within the hypothalamic‐pituitary‐adrenal (HPA) axis of H and NH animals under conditions of chronic stress. We, therefore, examined HPA function in adult H and NH rats exposed to chronic intermittent cold stress (4 h of 4°C cold a day for 21 days; H CHR and NH CHR) and in control H and NH (H CTL and NH CTL) rats. H CTL and NH CTL animals displayed comparable ACTH and B responses to a single, acute exposure to cold. We found that H CHR animals exhibited lower levels of ACTH, but not B, during the 21st exposure to cold (the homotypic stressor) compared to the first exposure to cold in H CTL; however, ACTH and B levels in NH CHR were not different from those in NH CTL. In contrast, NH CHR animals hypersecreted ACTH and B in response to restraint (the novel, heterotypic stressor) compared to NH CTL and both H groups, whereas H CHR and H CTL animals did not differ in their responses to restraint. These endocrine responses were associated with increased basal median eminence levels of both CRH and AVP in H CHR and NH CHR relative to their control groups (with NH CHR exhibiting the highest absolute levels of each secretagogue), and with decreased glucocorticoid receptor densities in septum of both H CHR and NH CHR. In addition, the expected lower glucocorticoid receptor density in hippocampus and frontal cortex of NH rats compared to H rats was observed. We believe that the difference in glucocorticoid receptor density between H and NH animals in the hippocampus and frontal cortex aid the associated differences in secretagogue content in the median eminence are related to the hypersecretion of ACTH and B in the NH CHR relative to the other groups. Furthermore, we hypothesize that an active inhibitory process is involved in the adaptation of HPA responses of H CHR animals to the homotypic stressor, and present a working model of regulation of activity within the CRH/AVP neurons in the PVN.
Journal of Neuroendocrinology - Tập 7 Số 2 - Trang 97-108 - 1995
Coexpression of Leptin Receptor and Preproneuropeptide Y mRNA in Arcuate Nucleus of Mouse Hypothalamus
Journal of Neuroendocrinology - Tập 8 Số 10 - Trang 733-735 - 1996
Chronic Administration of Leptin into the Lateral Ventricle Induces Sexual Maturation in Severely Food‐restricted Female Rats In many species, delayed sexual maturation occurs when metabolic conditions are not satisfactory. Recently, leptin was shown to be involved in the regulation of food intake and body mass. Furthermore, leptin administration was shown to advance sexual maturation in mice and to rescue sexual function in adverse metabolic conditions. We examined plasma leptin levels in female rats during development and evaluated the role of leptin on sexual maturation in rats subjected to food restriction. In normal rats, plasma leptin levels were low at day 24 of life, then steadily increased during the juvenile period, reaching 740 ±56 pg/ml at 40 days at time of vaginal opening (VO) and further increasing by day 60 (957±73 pg/ml). Food restriction initiated at day 25 strongly impaired this increase, in proportion to the severity of the restriction. With a daily food intake reduced to 7–8 g/day, that permanently prevented VO, plasma leptin levels were very low at day 53 (169 ±67 pg/ml). Following switch to ad libitum feeding, plasma leptin reached high levels within 2 days (1577±123 pg/ml), and VO occurred 4 days later. If the severe food restriction was maintained and a central infusion of leptin (10 μg/day) was initiated, a significant decrease in body weight compared with vehicle‐infused controls was observed. In these conditions, VO occurred in eight out of the nine leptin‐treated rats, representing induction of the process of sexual maturation confirmed by increases in ovarian and uterine weights. This induction of sexual maturation exclusively results from a central effect of leptin because no leak of the icv administered leptin to the general circulation was observed. These data suggest that the rising plasma levels of leptin in the prepubertal period represent a signal to the brain indicating that the young animal is metabolically ready to go through the process of sexual maturation.
Journal of Neuroendocrinology - Tập 10 Số 8 - Trang 627-633 - 1998
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