Prazosin blocks the glutamatergic effects of N-methyl-D-aspartic acid on lordosis behavior and luteinizing hormone secretion in the estrogen-primed female rat.
We have observed that intracerebroventricular (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 in lordosis. The interaction between LHRH and glutamate was previously explored by us and another groups. The noradrenergic 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 alpha1- and alpha2b-noradrenergic antagonist, was studied here by injecting it icv (1.75 and 3.5 microg/6 microL) prior to NMDA administration (1 microg/2 microL) 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 the lordosis/mount ratio at high doses (67.06 +/- 3.28, N = 28) when compared to saline controls (6 and 2 microL, 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 alpha-blockade than hormonal effects. These findings strongly suggest that the facilitatory effects of NMDA on both lordosis and LH secretion in this model are mediated by alpha-noradrenergic transmission.
Landa
A I
AI
Laboratorio de Neurociencias y Psicología Experimental, Facultad de Humanidades y Ciencias de la Educación, Universidad Católica Argentina, Mendoza, Argentina.
Cabrera
R J
RJ
Gargiulo
P A
PA
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D005260:Female; D007276:Injections, Intraventricular; D007986:Luteinizing Hormone / Q000097:blood* / Q000187:drug effects; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors; D009638:Norepinephrine / Q000378:metabolism; D010052:Ovariectomy; D011187:Posture / Q000502:physiology; D011224:Prazosin / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012726:Sexual Behavior, Animal / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects*
D000317:Adrenergic alpha-Antagonists; D016202:N-Methylaspartate; D007986:Luteinizing Hormone; D009638:Norepinephrine; D011224:Prazosin