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Cátedras de Fisiología y Fisiopatología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 1113 Buenos Aires, Argentina
The existence of
endothelin binding sites on the catecholaminergic neurons of the
hypothalamus suggests that endothelins (ETs) participate in the
regulation of noradrenergic transmission modulating various
hypothalamic-controlled processes such as blood pressure, cardiovascular activity, etc. The effects of ET-1 and ET-3 on the
neuronal release of norepinephrine (NE) as well as the receptors and
intracellular pathway involved were studied in the rat anterior hypothalamus. ET-1 (10 nM) and ET-3 (10 nM) diminished neuronal NE
release and the effect blocked by the selective ET type B receptor antagonist BQ-788 (100 nM).
N
-nitro-L-arginine methyl ester
(10 µM), methylene blue (10 µM), and KT5823 (2 µM), inhibitors of
nitric oxide synthase activity, guanylate cyclase, and protein kinase
G, respectively, prevented the inhibitory effects of both ETs on
neuronal NE release. In addition, both ETs increased nitric oxide
synthase activity. Furthermore, 100 µM picrotoxin, a
GABAA-receptor antagonist, inhibited ET-1 and ET-3
response. Our results show that ET-1 as well as ET-3 has an inhibitory
neuromodulatory effect on NE release in the anterior hypothalamus
mediated by the ET type B receptor and the involvement of a nitric
oxide-dependent pathway and GABAA receptors. ET-1 and ET-3
may thus diminish available NE in the synaptic gap leading to decreased
noradrenergic activity.
endothelin receptor; soluble guanylyl cyclase; BQ-610; BQ-788; GABAA receptor, nitric oxide, norepinephrine
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