Journal of neuroendocrinology
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J. Neuroendocrinol. · Jul 2009
ReviewGlial cells: indispensable partners of hypothalamic magnocellular neurones.
The hypothalamo-neurohypophysial system is comprised of magnocellular neurones that synthesise the neuropeptides oxytocin or vasopressin. As neurohormones, these peptides intervene in the regulation of vital functions such as parturition, lactation, osmotic and cardiovascular regulation. The release of these peptides in the general circulation depends on the electrical activity of their parent neurones, which in turn is regulated by the activity of their afferent inputs conveying distinct information. ⋯ An important gliotransmitter is the amino acid, d-serine, which, together with glutamate, activates NMDA receptors. Once activated, NMDA receptors govern the weight of individual inputs on magnocellular neurones and thus the impact of distinct types of information on neuronal activity. As reviewed here, numerous observations show that astrocytes must be considered as key elements in the functioning of the hypothalamo-neurohypophysial system.
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J. Neuroendocrinol. · Jul 2009
Ovarian-steroid modulation of locus coeruleus activity in female rats: involvement in luteinising hormone regulation.
The noradrenergic nucleus locus coeruleus (LC) has been reported to regulate luteinising hormone (LH) secretion in female rats. Both oestrogen and progestin receptors have been demonstrated in LC neurones, suggesting that these cells are possibly responsive to variations in circulating levels of ovarian steroids. We therefore evaluated changes in the activity of LC neurones during the oestrous cycle and after ovarian-steroid treatment in ovariectomised (OVX) rats, as determined by immunoreactivity to Fos-related antigens (FRA), which comprises all of the known members of the Fos family. ⋯ Bath application of progesterone significantly increased the spontaneous firing rate of OVX+E LC neurones. Our data suggest that ovarian steroids may physiologically modulate the activity of LC neurones in females, with possible implications for LH secretion. Moreover, oestradiol and progesterone appear to exert opposite and complementary effects (i.e. whereas oestradiol inhibits, progesterone, after oestradiol priming, stimulates LC activity).