Median Eminence Serotonin Involved in the Proestrus Gonadotropin Release

Ml, Vitale; M, de las Nieves Parisi; Chiocchio,; Jh, Tramezzani

doi:10.1159/000123969

Cited by 34 publications

(17 citation statements)

References 31 publications

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“…The DR has a serotonergic projection to the ME [20] and ME-5-HT content has been described to decrease in the af ternoon of proestrus [22]. The present report shows that after DR lesion, 5-HT in the ME drops by about 50%: in these animals 5-HT does not further decrease during proestrous afternoon.…”

Section: Discussionsupporting

confidence: 43%

“…However, recently, a stimulatory role of 5-HT on preovulatory gonadotropin release at the level of the hypo thalamus has been suggested [6,25,26]. 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].…”

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confidence: 99%

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

Vitale

Villar²,

Chiocchio³

et al. 1987

Neuroendocrinology

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The purpose of this study was to examine the role that the dorsal raphe (DR)-median eminence (ME) serotonergic projection may have in the proestrous gonadotropin and prolactin (PRL) release. DR electrolytic lesions were performed in cycling rats during the first day of diestrus. The effect of DR lesions after 48–72 h of survival (short-term lesioned animals) or after 35–40 days of survival (long-term lesioned animals) on estrous cyclicity, preovulatory gonadotropin and PRL releasing pattern, ovulation and serotonin (5-HT) content of the ME were studied. Following DR lesions the estrous cycle became irregular, remaining in the diestrus phase for several days. Preovulatory gonadotropin release in short-term lesioned animals was increased; on the contrary, in long-term lesioned rats a delay in the surge of these two hormones and a decrease in LH secretion were detected. Long-term lesioned animals also showed a diminished secretion of PRL. The number of ova did not differ between control and lesioned animals. DR lesions in both short- and long-term lesioned rats reduced 5-HT levels in the ME by about 50% and nullified the normal 5-HT decline during the afternoon of proestrus. Our results suggest that the DR exerts a stimulatory influence on the provulatory gonadotropin release by means of its 5-HT projection to the ME. As the pattern of hormonal secretion in lesioned animals remains similar to that of controls, it may be suggested that this pathway acts as a fine modulator of the mechanisms involved in the regulation of LH and FSH release in cycling rats. Our results also indicate that the DR plays a role in the release of PRL on proestrus.

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Section: Discussionsupporting

confidence: 43%

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confidence: 99%

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

Vitale

Villar²,

Chiocchio³

et al. 1987

Neuroendocrinology

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“…Others have suggested that the dual effect of 5HT is due to its exerting opposite effects at different sites. Recent evidence based on changes in 5HT turnover indi cates that the POA and ME are sites for the stimulatory action of 5HT on LH release [6,22,25,48,50] while it is inhibitory to both gonadotrophin release and sexual behaviour in the ARC [9,12] and the VMN [10,21,22], Alternatively, these dual effects may reflect the activation of different 5HT recep tors. Indeed, there is some evidence that 5HT is inhibitory to female sexual behaviour via 5HT| receptors and stimulatory via 5HT: receptors [2,32,33,55].…”

Section: Discussionmentioning

confidence: 99%

Differential Involvement of 5-Hydroxytryptamine (5HT) in Specific Hypothalamic Areas in the Mediation of Steroid-Induced Changes in Gonadotrophin Release and Sexual Behaviour in Female Rats

1989

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Ovariectomised rats were treated with either oestradiol benzoate (OB) alone or OB followed by progesterone (P). The effects of the steroid treatments were noted on plasma LH concentration, lordosis quotient and concentration of 5-hydroxytryptamine (5HT) and 5-hydroxyindole acetic acid (5HIAA) in microdissected hypothalamic areas, i.e. the preoptic area (POA), arcuate nucleus (ARC), median eminence (ME), ventromedial nucleus (VMN), suprachiasmatic nucleus (SCN) and zona incerta (ZI). The ratio of 5HIAA:5HT or parallel changes in the concentrations of 5HT and 5HIAA were taken as indices of 5HT neuronal activity. 5 µg OB alone reduced LH release and had no effect on receptivity. This treatment reduced 5HT activity in the SCN and raised it in the ZI. After 5 µg OB plus 0.5 mg P, all the rats exhibited an LH surge and full sexual receptivity. 5HT activity was significantly raised in the ME and reduced in the ARC, VMN and ZI. By using submaximal steroid regimes (2 µg OB plus 0.05 mg P, or 50 µg OB alone) correlations could be made between sexual behaviour, LH release and 5HT activity. There was no correlation between LH release and receptivity indicating that the two functions are controlled by different systems. Correlating 5HT activity in the various sites with the two physiological parameters indicated whether the changes seen after the maximal steroid treatment were concerned with behaviour, LH release or both. The results indicate that the changes seen in the VMN, ARC and ME are correlated with sex behaviour and those in the VMN and ZI with increased LH release. Oestrogen appears to stimulate behaviour by reducing 5HT activity in the ARC and P by reducing 5HT activity in the VMN and increasing it in the ME. Oestrogen seems to exert its feedback effects on LH by altering a stimulatory 5HT system in the SCN and an inhibitory one in the ZI. P stimulates LH release by reducing 5HT in the VMN and the ZI.

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“…The responsiveness of each neurotransmitter system to gonadal steroids in conjunction with its specific 1 A preliminary report of this work was given at the Society for Neuroscience Annual Meeting, Anaheim, California, October 10-14, 1984. Received: February 6, 1985 Accepted after revision: May 9, 1985 function in a given area of the hypothalamus and related brain areas is thought to provide the necessary mechanism through which these steroids modify numerous reproduc tive functions from sexual behavior to ovujation [31].Changes in 5-hydroxytryptamine (5HT; serotonin) con centrations [28, 29,38,45], 5HT| receptor binding [4] and 5HT uptake [32] have been demonstrated in various brain regions including the hypothalamus during the course of the estrous cycle in rats and mice. Concurrent with the surge in serum LH levels following the sequential adminis tration of estradiol (E^) and progesterone (P) to ovariecto mized rats [25,41], an increase both in 5HT concentration and 5HT synthesis is seen in the dorsal raphé nuclei [8].…”

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Effect of Ovarian Steroids to Stimulate Region-Specific Hypothalamic 5-Hydroxytryptamine Synthesis in Ovariectomized Rats

King

Steger

Morgan³

1986

Neuroendocrinology

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Accumulations of 5-hydroxytryptophan (5HTP) and L-dihydroxyphenylalanine (L-DOPA) following decarboxylase inhibition as indices for 5-hydroxytryptamine (5HT) and catecholamine (dopamine and/or norepinephrine) synthesis, respectively, were both increased in the preoptic area-anterior hypothalamus (POA-AH) of ovariectomized rats treated with a combination of 17β-estradiol benzoate (E2) and progesterone (P). Similarly, an increased accumulation of L-DOPA was seen in the mediobasal hypothalamus (MBH) and median eminence (ME) of these animals although no change was observed in 5HTP accumulation in the MBH or ME of these rats. Hypophysectomy negated these steroid-induced effects on L-DOPA accumulation. However, hypophysectomy had no apparent effect on steroid-stimulated 5HTP accumulation in the POA-AH of these rats. Under the experimental conditions of our study, the results suggest (1) that the stimulatory effect of ovarian steroids on hypothalamic catecholamine synthesis is dependent on an intact pituitary gland, (2) that the stimulatory effect of ovarian steroids on 5HT synthesis in the POA-AH is not dependent on an intact pituitary gland, and (3) that ovarian steroids do not seem to influence 5HT synthesis in the ME or MBH. The significance of these results may lie in the function of these hypothalamic monoaminergic neurotransmitter systems to regulate gonadotrophin release and subsequent steroid feedback modulation of such central regulatory mechanisms.

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Median Eminence Serotonin Involved in the Proestrus Gonadotropin Release

Cited by 34 publications

References 31 publications

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

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

Differential Involvement of 5-Hydroxytryptamine (5HT) in Specific Hypothalamic Areas in the Mediation of Steroid-Induced Changes in Gonadotrophin Release and Sexual Behaviour in Female Rats

Effect of Ovarian Steroids to Stimulate Region-Specific Hypothalamic 5-Hydroxytryptamine Synthesis in Ovariectomized Rats

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