The NMDA receptor complex modulates clonidine-induced increases in growth hormone levels in rats.
Intraperitoneal administration of clonidine (50 micrograms/kg) produced increases in growth hormone levels in male Wistar rats. Pretreatment with NMDA receptor antagonists including (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP/NMDA site), ifenprodril (polyamine site), and dizocilpine maleate (MK-801) or phencyclidine (PCP) (channel blockers) did not have any significant effect on clonidine-induced increases in growth hormone levels. In contrast, pretreatment with 5,7-dichlorokynurenic acid and 6,7-dinitroquinoxaline-2,3-dione (DNQX) (NMDA receptor-associated glycine site antagonists) significantly attenuated clonidine-induced increases in growth hormone levels. Attenuation of clonidine's effect on growth hormone levels by NMDA receptor-associated glycine site antagonists appears most likely due to an interaction between their effects on the NMDA receptor complex with growth hormone releasing factor.
Mazzola-Pomietto
P
P
Laboratory of Clinical Science, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA.
Aulakh
C S
CS
Murphy
D L
DL
D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D013006:Growth Hormone / Q000097:blood*; D007736:Kynurenic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018009:Receptors, Glycine / Q000037:antagonists & inhibitors; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*
D011810:Quinoxalines; D018009:Receptors, Glycine; D016194:Receptors, N-Methyl-D-Aspartate; C056723:FG 9041; D013006:Growth Hormone; D007736:Kynurenic Acid; D003000:Clonidine; C066192:5,7-dichlorokynurenic acid