Jy. Seong et al., EFFECT OF GABAERGIC COMPOUNDS ON GONADOTROPIN-RELEASING-HORMONE RECEPTOR GENE-EXPRESSION IN THE RAT, Endocrinology, 136(6), 1995, pp. 2587-2593
Using a competitive reverse transcription-polymerase chain reaction (R
T-PCR), the amounts of GnRH receptor (GnRHR) transcript in a discrete
nucleus micropunched from rat brain slices were determined. GnRHR tran
script was highly expressed in anterior pituitary >> median eminence >
posterior mediobasal hypothalamus (pMBH) > preoptic area (POA) but no
t in cortex and posterior pituitary, which were used as control tissue
s. To examine the effect of GABA on GnRHR transcript level, 10 nmol of
muscimol, a GABA-A receptor agonist, or baclofen, a GABA-B receptor a
gonist, was microinjected into the lateral ventricle of ovariectomized
rats. Two hours after an intraventricular injection, rats were decapi
tated. Blood was collected 1 h before and after drug administration an
d used for LH determination. Serum LH levels were significantly reduce
d by muscimol but not by baclofen within 2 h. The activation of GABA-A
receptors with muscimol resulted in a significant inhibition in GnRHR
transcript level in both the pMBH and POA but not in the pituitary: T
he activation of GABA-B receptors with baclofen, however, did not prod
uce any effect on GnRHR transcript level in the pMBH and POA, as well
as the pituitary. This experiment demonstrates for the first time that
GABAergic neurotransmission, through GABA-A receptors, is involved in
the regulation of GnRHR transcript level in the rat hypothalamus. Thi
s suggests that GABAergic neurotransmission regulates GnRHR gene expre
ssion in a coordinated, yet complex, fashion in the control of the neu
roendocrine function of GnRH-LH axis.