Prazosin blocks the glutamatergic effects of N-methyl-D-aspartic acid on lordosis behavior and luteinizing hormone secretion in the estrogen-primed female rat.

LANDA, A.I.; CABRERA, R.J.; GARGIULO, P.A.

BRAZILIAN JOURNAL OF MEDICAL AND BIOLOGICAL RESEARCH

Associação Brasileira de Divulgação Científica.

Lugar: Ribeirao Preto. Sao Paulo. ; Año: 2006 vol. 39 p. 365 - 370

0100-879X

Landa, A.I.; Cabrera, R.J.; Gargiulo, P.A. Prazosin blocks NMDA glutamatergic effects of N-methyl-D-aspartic acid on lordosis behavior and luteinizing hormone secretion in the estrogen-primed female rat. Brazilian Journal of Medical and Biological Research (2006): 39: 365-370. We have observed that intracerebroventruicular (icv) injection of selective N-Methyl-D-Aspartic-Acid (NMDA)-type glutamatergic receptor antagonists inhibits lordosis in ovariectomized (OVX), estrogen-primed rats receiving progesterone or Luteinizing Hormone Releasing Hormone (LHRH). When NMDA was injected into OVX estrogen-primed rats, it induced a significant increase of lordosis. The intereacion between LHRH and glutamate was previously explored by us and another groups. The noredrenergic systems have a functional role in the regulation of LHRH release. The purpose of the present study was to explore the interaction between glutamatergic and noradrenergic transmission. The action of prazosin, an á1 and  á2b-noradrenergic antagonist, was studied here by injecting it icv (1.75 and 3.5 ìg/6 ìl) prior to NMDA  administration (1 ìg/2 ìl) in OVX estrogen-primed Sprague-Dawley rats (240-270 g). Rats manually restrained were injected over a period of 2 min, and tested 1.5 h later. The enhancing effect induced by NMDA on lordosis/mount ratio at high doses (67.06 ± 3.28, N=28) when compared to saline controls (6 and 2 , ìl, 16.59 ± 3.20, N=27) was abolished by prazosin administration (17.04 ± 5.52, N=17, and 9.33 ± 3.21, N=20, P<0.001 for both doses). Plasma LH levels decreased significantly only with the higher dose of prazosin (1.99 ± 0.24 ng/ml, N=18, compared to saline-NMDA effect, 5.96 ± 2.01 ng/ml, N=13, P<0.05). Behavioral effects seem to be more sensitive to the á–blockade than hormonal effects. These findings strongly suggest that the facilitatory effects of NMDA on both lordosis and LH secretion in this moedel are mediated by á-noradrenergic transmission. KEY WORDS: Sexual behavior, Glutamate, Luteinizing hormone, Noradrenergic transmission, Prazosin, N-methyl-D-aspartic acid