Abstract
Previous indicate results that the dopaminergic system in the anterior media zona incerta (ZI) exerts effect on LH release. In this report changes in dopamine (DA) turnover in the ZI, preoptic area (POA) and arcuate/median eminence area (ARC/ME) (as assessed by the rate of decline in DA concentration after γ-methyl- p-tyrosine) have been noted each afternoon (16.00–18.00 h) of the 4 days of the oestrous cycle and also on the morning (9.00–11.00 h) of proestrus (P) and second day of dioestrus (D 2). Over the time of the preovulatory LH surge on P, a significant rise in DA turnover was observed in the ZI. As this area contains components of the dopaminergic incerto-hypothalamic (I-H) tract, this studyprovides evidence to implicate the I-H tract in the physiological stimulation of the preovulatorysurge of LH on proestrus. Selective destruction of DA nerve terminals (with 6-hydroxydopamine plus desmethylimipramine) and the various cell bodies (with ibotenic acid) in the ZI both induced a period of dioestrus (9–11 days). The similarity of effect of these two types of lesion indicate that the DA nerve terminals in the ZI stimulate a stimulatory pathway ultimately to induce LH release.
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