Ethanol-induced alterations in beta-endorphin levels in specific rat brain regions: modulation by adenosine agonist and antagonist.
Previous studies in our laboratory have indicated that ethanol alters beta-endorphin (beta-EN) levels in specific rat brain regions. The present investigation was conducted to evaluate the effects of an adenosine agonist and an adenosine antagonist on these alterations. Male Sprague-Dawley rats weighing 150-200 g were used in this study. The animals were injected intraperitoneally at 11.00 h with ethanol (3 g/kg as a 22.5% w/v solution in saline), N6-cyclohexyladenosine (CHA; 0.1 mg/kg), theophylline (30 mg/kg), a combination of ethanol and CHA, or a combination of ethanol and theophylline. The control rats received saline. The animals were sacrificed 1 h after injection. Frontal cortex (CTX), hypothalamus (HY), hippocampus (HI), and midbrain (MB) were dissected, and their beta-EN levels were determined by radioimmunoassay. Ethanol administration significantly increased the beta-EN levels in HY (39% increase), HI (28% increase), and MB (19% increase), but had no effect in CTX. The adenosine agonist (CHA) produced similar significant increases in beta-EN levels in HY and MB, but did not alter these levels in CTX or HI. In contrast, the adenosine antagonist theophylline did not alter beta-EN levels in any brain region studied. However, theophylline pretreatment significantly reduced ethanol-induced changes in beta-EN levels in HY, completely blocked ethanol effects in HI, and reversed ethanol alterations in MB. On the other hand, CHA, concurrently administered with ethanol, potentiated ethanol-induced increases of beta-EN levels in HY and HI. These findings suggest that the ethanol-induced increases in beta-EN levels in specific rat brain regions may be modulated by adenosinergic compounds and that adenosine receptors may play a role in ethanol effects on rat brain levels of beta-EN.
Anwer
J
J
College of Pharmacy and Pharmaceutical Sciences, Florida A. & M. University, Tallahassee, USA.
Soliman
M R
MR
D000241:Adenosine / Q000008:administration & dosage / Q000819:agonists / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D004347:Drug Interactions; D000431:Ethanol / Q000008:administration & dosage / Q000633:toxicity*; D005625:Frontal Lobe / Q000187:drug effects / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D007274:Injections, Intraperitoneal; D008297:Male; D008636:Mesencephalon / Q000187:drug effects / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D013806:Theophylline / Q000008:administration & dosage / Q000494:pharmacology; D001615:beta-Endorphin / Q000378:metabolism*
C027513:N(6)-cyclohexyladenosine; D000431:Ethanol; D001615:beta-Endorphin; D013806:Theophylline; D000241:Adenosine