Reversal by estrogen of the effect of dorsal raphe stimulation on release of LH but not prolactin

Kitts, C S; Johnson, James H.

doi:10.1002/jnr.490150214

Cited by 13 publications

(13 citation statements)

References 19 publications

(4 reference statements)

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“…The present results are consistent with previous reports of inhibitory effects of serotonin administration [15,19] or of activation by electrical stimulation of inhibitory path ways [1,8,17] on tonic LH release in gonadectomized rats, as well as with suggested stimulatory influences of seroto nin in the presence of estrogen [7,11,17], Unmasking of an inhibitory response to 5MEODMT by antagonism of 5HT: receptors provides evidence for activities in the ovariectomized animal of opposing modulatory influences mediated by 5FIT) and 5HTj receptors, both of which appear to be activated by systemic administration of 5MEODMT. Sim ilarly, the fact that in EB-primed animals morphine signifi cantly stimulated LH release only following the blockade of 5HTt receptors by KET provides further evidence for this dual receptor system, and suggests that the balance be tween them is shifted markedly by the steroid in favor of the stimulatory influence.…”

Section: Discussionsupporting

confidence: 83%

“…This phenomenon may be invoked to explain the differences in results observed in EB-primed animals versus unprimed ovariectomized animals: the can cellation of a significant morphine-induced decline in LH, and a reversal of a downward trend and replacement with a significant increase in response to 5MEODMT. The net stimulatory influence of 5HTagonism on LH release in EBprimed animals is in agreement with steroid modulation of responses to stimulation of the arcuate nucleus of the hypo thalamus [7] or dorsal raphe nucleus [17], and might suggest a common mechanism. Unfortunately, the magnitude of the estrogen-induced increase in sensitivity of the stimulatory mechanism precludes a definitive conclusion concerning which species of 5HT receptor might mediate the stimula tory effects of 5MEODMT in the presence of estrogen.…”

Section: Discussionsupporting

confidence: 59%

“…Estrogen was found to re verse the direction of the response to electrical stimulation of the arcuate nucleus, perhaps mediated by serotonin [7], as well as to stimulation of the dorsal raphe nucleus [17], Morphine has long been known to inhibit tonic LH release [5] as well as to block the preovulatory surge [2], and release of LH following administration of naloxone has been shown to involve serotonin [12]. In the present experiments we have explored interactions between opiate and seroton ergic systems by studying effects on LH release of various Received: February 13, 1985 Accepted after revision: March 19, 1986 combinations of a 5HT agonist or antagonist with the op iate agonist morphine.…”

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confidence: 99%

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Evidence for Multiple Serotonergic Influences on LH Release in Ovariectomized Rats and for Modulation of Their Relative Effectiveness by Estrogen

1986

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Both opiates and serotonin (5HT) are known to inhibit LH release in ovariectomized rats, and estrogen has been shown to reverse certain serotonergic effects. Therefore studies were undertaken to compare the effects of morphine and the serotonin agonist 5-methoxy-NN-dimethyltryptamine (5MEODMT) on LH release in ovariectomized rats with and without estrogen priming. Serial blood samples were collected via jugular cannulae before and 5, 15, 30 and 60 min after intravenous administration of morphine, 5MEODMT or both to rats receiving no pretreatment, or a serotonin receptor antagonist (methysergide, METH; or ketanserin, KET) 60 min earlier. In the absence of estrogen, morphine inhibited LH release, and the response was delayed by METH or abolished by KET, suggesting mediation by serotonin₂ (5HT₂) receptors. 5MEODMT alone failed to alter the release of LH significantly, but apparently activated both stimulatory and inhibitory serotonergic systems. Blockade of 5HT₂ receptors with KET enabled an inhibitory system to prevail. No significant changes in LH concentrations were observed following combined administration of morphine and 5MEODMT. Similarly, in estrogen-primed rats morphine appeared to activate both inhibitory (5HT₂) and stimulatory (5HT₁) systems, resulting in no net change unless the inhibitory system had been antagonized by KET. Administration of 5MEODMT alone or in combination with morphine resulted in a strong stimulatory effect which appeared to be mediated by 5HT₁ receptors. These results suggest the existence of a multiplicity of serotonergic influences on the release of LH in the rat, not only in terms of particular species of 5HT receptors, but also in neuronal connectivity. Finally, it is clear that the responses to morphine and 5MEODMT are not only not equivalent, but are mediated by different mechanisms whose effects are integrated downstream in order to produce the observed effects on LH release.

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Section: Discussionsupporting

confidence: 83%

Section: Discussionsupporting

confidence: 59%

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confidence: 99%

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Evidence for Multiple Serotonergic Influences on LH Release in Ovariectomized Rats and for Modulation of Their Relative Effectiveness by Estrogen

1986

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“…In fact, the resumption of estrous cycles was accompanied by a delay in the preovulatory surges of LH and FSH and by a decrease in their serum concentrations. Similar changes have been observed in other experimental models [5,8,19].…”

Section: Discussionsupporting

confidence: 75%

“…The DR has been shown to participate in Received: October 17, 1986 Accepted after revision: March 20. 1987 the control of luteinizing hormone (LH) release [1,5,8,10,19,27], However, because of the wide variety of experimen tal models and strategies used in these studies, its physio logical role deserves further clarification. Moreover, the hypothalamic region through which the DR projections exert this control is still unknown.…”

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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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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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Comparative study of the sources of neuronal projections to the site of gonadotrophin-releasing hormone perikarya and to the anteroventral periventricular nucleus in female rats

Hahn

Coen

2005

J. Comp. Neurol.

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The rat ovulatory cycle is dependent on the preoptic region encompassing the gonadotrophin-releasing hormone (GnRH) perikarya and the anteroventral periventricular nucleus (AVPV). Retrograde tract tracing was used to identify and compare the sources of inputs to these sites in female rats. Within the telencephalon and diencephalon, the incidence of retrograde labelling from both sites was moderate to abundant in the ventral lateral septum, posteromedial bed nucleus of the stria terminalis, amygdalohippocampal area and the periventricular, medial preoptic, anterodorsal preoptic, dorsomedial suprachiasmatic, arcuate, and posterior ventrolateral ventromedial hypothalamic nuclei. In these regions, the incidence of retrograde labelling was either greater from the AVPV than from the GnRH perikarya site or similar from both sites. In the medial amygdaloid, parastrial, striohypothalamic, and ventral premammillary nuclei, the retrograde labelling from the AVPV greatly exceeded the sparse incidence from the GnRH perikarya site. In contrast, retrograde labelling from the GnRH perikarya site predominated in the median preoptic, lateroanterior and dorsomedial hypothalamic nuclei, subparaventricular zone, and retrochiasmatic area; it was abundant in the AVPV. Caudal to the diencephalon, retrograde labelling from either site was sparse, except in the lateral parabrachial nucleus, which displayed a particularly high incidence from the GnRH perikarya site. Other mesencephalic regions labelled from either site included the periaqueductal gray and dorsal and median raphe nuclei. The most caudal labelling was found in the ventrolateral medulla and region of the solitary tract nucleus; this was almost exclusively from the GnRH perikarya site. These findings further elucidate the neuroanatomical connections underlying the control of the ovulatory cycle.

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Reversal by estrogen of the effect of dorsal raphe stimulation on release of LH but not prolactin

Cited by 13 publications

References 19 publications

Evidence for Multiple Serotonergic Influences on LH Release in Ovariectomized Rats and for Modulation of Their Relative Effectiveness by Estrogen

Evidence for Multiple Serotonergic Influences on LH Release in Ovariectomized Rats and for Modulation of Their Relative Effectiveness by Estrogen

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

Comparative study of the sources of neuronal projections to the site of gonadotrophin-releasing hormone perikarya and to the anteroventral periventricular nucleus in female rats

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