Endocrinology, Vol 137, 5297-5302, Copyright © 1996 by Endocrine Society

ARTICLES

An interactive physiological role of neuropeptide Y and galanin in pulsatile pituitary luteinizing hormone secretion

B Xu, S Pu, PS Kalra, JF Hyde, WR Crowley and SP Kalra
Department of Neuroscience, University of Florida College of Medicine, Gainesville 32610, USA.

Both neuropeptide Y (NPY) and galanin (GAL) systems have been implicated in the excitatory regulation of pulsatile LH secretion in the ovariectomized rat. The present studies were designed to examine the possible interaction of these two neuropeptides in controlling episodic LH release by testing the effects of central infusion of antibodies (Ab) to NPY and GAL, alone or in combination; additional studies tested the effects of central administration of an antisense oligodeoxynucleotide (ODN) to NPY and GAL messenger RNA. Rats were ovariectomized, implanted with a cannula in the third ventricle, and used in experiments 2 weeks later. Central infusion, via Alzet osmotic minipumps, of IgG purified from an NPY Ab produced a dose-related suppression of pulsatile LH secretion. Although an Ab dilution of 1:10 was ineffective, a maximal inhibitory effect was obtained using an NPY Ab dilution of 1:1, which decreased the mean levels, pulse frequency, and pulse amplitude of LH. These parameters of episodic LH secretion were also significantly reduced by central injection of antisense NPY ODN compared to those in vehicle- or missense ODN-treated controls. Similar dose-related inhibitory effects on the parameters of LH secretion were seen after central infusion of GAL Ab. Furthermore, infusion of a combination of NPY Ab and GAL Ab, each at the ineffective dilution of 1:10, resulted in a profound inhibition of LH secretion equivalent to the pattern seen with the maximally effective 1:1 Ab dilution. These results strengthen the idea of a physiological role for both NPY and GAL systems in the mechanism underlying the LHRH pulse generator activity and further suggest that these two excitatory neuropeptides act in concert to generate pulsatile LHRH release.

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