B. Xu et al., AN INTERACTIVE PHYSIOLOGICAL-ROLE OF NEUROPEPTIDE-Y AND GALANIN IN PULSATILE PITUITARY LUTEINIZING-HORMONE SECRETION, Endocrinology, 137(12), 1996, pp. 5297-5302
Both neuropeptide Y (NPY) and galanin (GAL) systems have been implicat
ed in the excitatory regulation of pulsatile LH secretion in the ovari
ectomized rat. The present studies were designed to examine the possib
le interaction of these two neuropeptides in controlling episodic LH r
elease by testing the effects of central infusion:of antibodies (Ab) t
o 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, implant
ed with a cannula in the third ventricle, and used in experiments 2 we
eks later. Central infusion, via Alter osmotic minipumps, of IgG purif
ied 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 re
duced by central injection of antisense NPY ODN compared to those in v
ehicle- or missense ODN-treated controls. Similar dose-related inhibit
ory effects oh the parameters of LH Secretion were seen after central
infusion of GAL Ab. Furthermore, infusion of a combination of NPY Ab a
nd GAL Ab, each at the ineffective dilution of 1:10, resulted in a pro
found inhibition of LH Secretion equivalent to the pattern seen with t
he maximally effective 1:1 Ab dilution. These results strengthen the i
dea of a physiological role for both NPY and GAL systems in the mechan
ism underlying the LHRH pulse generator activity and further Suggest t
hat these two excitatory neuropeptides act in concert to generate puls
atile LHRH release.