Serotonin induces gonadotrophin release through stimulation of LH-releasing hormone release from the median eminence

Abstract

The effects of serotonin (5-HT) on the release of gonadotrophins and LH-releasing hormone (LHRH) were examined in an in-vitro perifusion system using median eminences and/or anterior pituitaries obtained from male or pro-oestrous female rats. Animals were killed by decapitation between 12.00 and 13.00 h. A serial double-chamber perifusion system was employed. Three types of experiments were performed. In the first, median eminences were placed in the first chamber and one anterior pituitary in the second chamber. In the second group, only the anterior pituitary was perifused. In the third group, only five median eminences were perifused. In the first and second experiments, LH, FSH and prolactin were determined in the perifusion efflux by radio-immunoassay (RIA). In the third experiment, LHRH was determined by RIA. Addition of 5-HT (final concentrations 0.06, 0.6 and 6.0 mumol/l) into the first chamber containing the median eminences stimulated the release of LH and FSH from the pituitary, but did not affect the levels of prolactin in the effluent in the same experiment (pro-oestrous rats). The stimulatory effect of 5-HT was blocked by the addition of cyproheptadine (l mumol/l) in the perifusion fluid. The introduction of 5-HT (0.6 mumol/l) into the tube connecting the first and second chambers did not modify the release of LH, nor did 5-HT added to the pituitaries perifused alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Dorsal Raphe Lesion Alters the Estrous Cycle and the Preovulatory Gonadotropin Release

“…This interpretation is in agreement with previous results showing a stimulation of LH-RH release when ME from proestrous rats are perifused with 5-HT [24], A decrease in the 5-HT content of the ME was also found in animals sac rificed on the first proestrus immediately after the lesion (48-72 h). However, a slight but significant increase in LH and FSH surges was detected; this is opposed to the result observed in long-term lesioned animals.…”

“…The decline of 5-HT content and the increase of 5-HT turnover in the median eminence (ME) in the afternoon of proestrus led us to propose the ME as a site where this stimulatory influence takes place [22]. This assumption was supported by an in vitro approach in which the addition of 5-HT to perifused ME from proestrous rats significantly increased LH-RH re lease [23,24].There is clear evidence that the 5-HT content of the ME largely depends upon dorsal raphe nucleus (DR) projec tions [12,13,20]. The DR has been shown to participate in Received: October 17, 1986 Accepted after revision: March 20.…”

Effects of DPDPE (a specific delta-opioid receptor agonist) and naloxone on hypothalamic monoamine concentrations during the pre-ovulatory LH surge in the rat

“…Their stimulatory effects are thought to be mediated in the MPOA in particular (31)(32)(33)(34). NA may also be stimulatory in the ME and ARN (32) and 5HT in the ME (35). Our own findings support the stimulatory effects of 5HT in the MPOA and ME and NA in the ARN, since the ratio of metabolite to neurotransmitter was greater in those animals showing an LH surge than in those where the LH surge was absent.…”

Estrogenic environmental endocrine-disrupting chemical effects on reproductive neuroendocrine function and dysfunction across the life cycle

“…Notably, the pubertal increase in pulsatile GnRH release is driven at least in part by alterations in afferent inputs from numerous neuropeptides, neurotrophic factors, and neurotransmitters [1]. Among these neurotransmitters is serotonin, which modulates LH secretion through actions on hypothalamic GnRH neurons [52]. Activity of the ratelimiting enzyme in serotonin synthesis, tryptophan hydroxylase (TPH) was reduced in the hypothalamus of pubertal male rats acutely exposed to A1254 [53], suggesting that the stimulatory effect of serotonin on GnRH-induced LH secretion may be disrupted by PCB inhibition of TPH.…”