The LHRH system in normal and neonatally androgenized female rats

King, Joan C.; Tobet, Stuart A.; Snavely, F.L.; Arimura, Akira

doi:10.1016/0196-9781(80)90106-0

Cited by 65 publications

(26 citation statements)

References 26 publications

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“…The lack of a detectable alteration in immunoreactive LHRH fiber staining has also been observed for persistent estrous rats induced by neonatal androgenization (King et al, 1980) or by aging (Merchenthaler et al, 1980b). Furthermore, in our study there was no concentration of LHRH perikarya or fibers in the MPN, although some perikarya and fibers were distributed in the areas lateral and dorsal to the MPN.…”

Section: Discussionmentioning

confidence: 37%

The LHRH neuronal system in female rats: Relation to the medial preoptic nucleus.

Terasawa¹,

Davis²

1983

Endocrinol Japon

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Previously we have found that small lesions confined to the medial preoptic nucleus (MPN) or the suprachiasmatic nucleus (SCN) blocked the cyclic release of gonadotropins in the female rat, inducing a persistent estrous state. Since the MPN is located just caudal to the organum vasculosum of the lamina terminalis (OVLT) where LHRH cell bodies are most concentrated, we applied an immunocytochemical technique to examine the possibility that the lesions had simply disrupted LHRH neurons or fibers.Using a new anti-LHRH provided by Dr. V. D. Ramirez, we found that the distribution pattern of immunoreactive LHRH cell bodies and fibers was similar to that previously reported, although the staining was more intense and extensive with low background.There was no concentration of LHRH cell bodies and fibers in the MPN or SCN and, in fact, these nuclei generally showed a lower density of stained elements than did sorrounding tissue. In persistent estrous animals with lesions confined to the MPN there was no detectable reduction of staind fibers in the median eminence.These results, along with the results of other workers, suggest that persistent estrus following lesions of the MPN or SCN is not due to reduction of LHRH neurons or fibers. Rather, they support the hypothesis that these nuclei are critical for triggering the ovulatory release of LHRH.

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Section: Discussionmentioning

confidence: 37%

The LHRH neuronal system in female rats: Relation to the medial preoptic nucleus.

Terasawa¹,

Davis²

1983

Endocrinol Japon

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“…However, proges tin-concentrating neurons of the rostral hypothalamus are found predominantly within the prcoptic portion of the su prachiasmatic region. Therefore, anovulatory persistent es trus and blockade of P-positive feedback observed follow ing MPN-L and similar lesions might be due to destruction of an intermediary population of P-sensitive neurons affer ent to the more diffusely organized GnRH system [17,18]. SCN lesions were also associated with anovulatory per sistent estrus.…”

Section: Discussionmentioning

confidence: 98%

“…completely block ovulation and P-induced LH release in the hamster [29], another rodent that, like the rat, has a 4-day ovulatory cycle in which the preovulatory gonadotropin surge is entrained by environmental illumination. Finally, recent lesion and immunocytochemical studies [14,[16][17][18] have demonstrated that GnRH-containing fibers, although located near midline at the level of the preoptic recess, do not pass through the SCN but lateral and dorsal to this nu cleus. Taken together, these observations suggest that defic its in reproductive function observed following lesions rea-sonably well restricted to the SCN are not due to direct in volvement of the preopticoinfundibular GnRH fiber system but are a consequence of destruction of the SCN perse.…”

Section: Discussionmentioning

confidence: 99%

Discrete Lesions Reveal Functional Heterogeneity of Suprachiasmatic Structures in Regulation of Gonadotropin Secretion in the Female Rat

Wiegand¹,

Terasawa²

1982

Neuroendocrinology

335

192

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The present study examines the function of several cytologically distinct suprachiasmatic structures in the regulation of ovulation and positive feedback effects of estrogen and progesterone on gonadotropin release in the rat. Small (0.6–0.8 mm dia.) electrolytic lesions were placed at four loci along the rostrocaudal extent of the suprachiasmatic region in regularly cycling female rats. Anovulatory persistent estrus occurred only when lesions were located either in the suprachiasmatic nucleus (SCN) or the medial preoptic nucleus (MPN), a small periventricular cell group lying immediately caudal to the organum vasculosum lamina terminalis (OVLT). Lesions restricted to the OVLT and adjacent ventral prechiasmatic region (VPC-L), or the anterior suprachiasmatic region (ASR) between the MPN and SCN resulted in irregular estrous cycles frequently marked by periods of prolonged diestrus. Following administration of 50 µg estradiol benzoate (EB) a daily afternoon surge of gonadotropin was observed in control animals. This circadian release of gonadotropins was completely abolished by SCN, ASR and MPN lesions. EB-induced gonadotropin surges were also greatly attenuated by VPC-L lesions. Subsequent administration of 1.5 mg progesterone (P) induced large surges of luteinizing hormone and follicle-stimulating hormone in VPC-L and ASR lesioned animals as well as controls. P administration also elicited gonadotropin surges in SCN lesioned animals, although surges were markedly attenuated in magnitude compared to controls. Only lesions that destroyed the MPN and immediately adjacent periventricular tissue completely and invariably eliminated P-induced gonadotropin release. Thus, anovulatory persistent estrus appears to be associated specifically with lesions that interfere with the positive feedback effect of P (MPN and SCN lesions). Animals with lesions that block or attenuate EB effects without interfering with P sensitive neural substrates can maintain long-term spontaneous ovulation (VPC-L and ASR lesions). An hypothesis is advanced to account for the differential effect of MPN and SCN lesions on P-induced gonadotropin release.

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“…The ceil bodies of some of these neuroendo crine factors, such as growth hormone releasing hormone and the prolactin inhibiting factor, dopamine, are concentrated in the ARC [3][4][5]. In other cases, the somata of the neuroendo crine cells are located in other hypothalamic nuclei or are dis tributed throughout the hypothalamus and preoptic area [6][7][8][9][10]. Reciprocal pathways between the ARC and these neuro secretory areas have been documented [for review see I ].…”

mentioning

confidence: 99%

Neurons in the Rat Arcuate Nucleus Are Hyperpolarized by GABA<sub>B</sub> and μ-Opioid Receptor Agonists: Evidence for Convergence at a Ligand-Gated Potassium Conductance

Loose

Rønnekleiv

Kelly³

1991

Neuroendocrinology

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Both γ-aminobutyric acid (GABA) and the endogenous opioid peptides have pervasive effects on neuroendocrine function. This study examined the effects of selective activation of GABAB and/or µ-opioid receptors on neurons of the arcuate nucelus (ARC) of the rat hypothalamus using intracellular recording of cells in a hypothalamic slice. Some recorded neurons were filled with biocytin allowing subsequent identification and immunocytochemical evaluation for the presence of β-endorphin. ARC neurons exhibited a broad array of active and passive conductances. Tyr-D-Ala-Gly-MePhe-Gly-ol (DAGOL), a µ-opioid receptor agonist, inhibited spontaneous firing, hyperpolarized 68% of ARC cells in a dose-dependent manner and increased cell conductance. Baclofen, a GABAB receptor agonist, hyperpolarized all cells tested. The reversal potentials for both the DAGOL- and baclofen-induced currents were near that of a potassium conductance. Maximal activation by either of the agonists blocked the effects of the other agonist. Identified β-endorphin cells were inhibited by both DAGOL and baclofen. The results of these in vitro studies suggest that GABAB and µ-opioid receptors are coupled to the same set of potassium channels and that these channels directly and powerfully inhibit most ARC cells, including β-endorphin neurons. We propose that convergence of inhibitory influences at the ligand-gated potassium conductance described here may be an important site of interaction for opioidergic, GABAergic and other putative neurotransmitter systems in the control of neuroendocrine circuits by the ARC.

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The LHRH system in normal and neonatally androgenized female rats

Cited by 65 publications

References 26 publications

The LHRH neuronal system in female rats: Relation to the medial preoptic nucleus.

The LHRH neuronal system in female rats: Relation to the medial preoptic nucleus.

Discrete Lesions Reveal Functional Heterogeneity of Suprachiasmatic Structures in Regulation of Gonadotropin Secretion in the Female Rat

Neurons in the Rat Arcuate Nucleus Are Hyperpolarized by GABA<sub>B</sub> and μ-Opioid Receptor Agonists: Evidence for Convergence at a Ligand-Gated Potassium Conductance

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