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Sustained Intermittent Release of Gonadotropin-Releasing Hormone in the Prepubertal Male Rhesus Monkey Induced by N-Methyl-DL-Aspartic Acid

 

作者: Vernon L. Gay,   Tony M. Plant,  

 

期刊: Neuroendocrinology  (Karger Available online 1988)
卷期: Volume 48, issue 2  

页码: 147-152

 

ISSN:0028-3835

 

年代: 1988

 

DOI:10.1159/000125002

 

出版商: S. Karger AG

 

关键词: Luteinizing hormone;Gonadotropin-releasing hormone;Puberty;Rhesus monkey;Hypothalamic Stimulation;Neuroexcitatory amino acid

 

数据来源: Karger

 

摘要:

The purpose of the present study was to determine whether gonadotropin-releasing hormone (GnRH) neurons in the hypothalamus of the prepubertal monkey may be prematurely provoked into producing a sustained train of intermittent GnRH release. N-methyl-DL-aspartic acid (NMA), an analog of the putative excitatory neurotransmitter aspartate, was used to stimulate the hypothalamus. In order to utilize pituitary luteinizing hormone (LH) secretion as a bioassay of hypothalamic GnRH release, juvenile males were castrated and the responsiveness of their gonadotrophs to GnRH was enhanced prior to the study with a chronic intermittent intravenous infusion of the synthetic decapeptide (0.1 µg/min for 3 min every hour). Treatment with this regimen of GnRH, which appears to provide the pituitary gonadotrophs with a hypophysiotropic stimulus similar to that produced by the hypothalamus of castrated adults, elicited a pattern of pulsatile LH secretion in prepubertal animals similar to that observed in the open-loop situation in adults. This episodic pattern of LH release was sustained without decrement following termination of GnRH priming and initiation of an intermittent intravenous infusion of NMA (4.5–6.5 mg NMA/kg body weight/pulse, administered over 1 min) delivered at a frequency of 1 pulse/1 h for 50 h. In contrast, an intermittent infusion of the vehicle employed to administer NMA (saline) failed to maintain LH secretion. Administration of the same dose of NMA at a slower frequency of 1 pulse/2 h for 52 h, while also sustaining LH secretion without decrement, resulted in an exaggeration in the LH response. Since it has been previously established that NMA-induced release of LH is mediated by hypothalamic GnRH, these results demonstrate that in the monkey GnRH neurons possess the potential for sustaining an adult-like pattern of intermittent GnRH release well before the onset of puberty. The foregoing findings are discussed in the context of current understanding of the neuroendocrine mechanisms underlying the prepubertal hiatus in gonadotropin secretion in primat

 

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