Effect of long-term ethanol feeding on brainstem alpha(2)-receptor binding in Wistar-Kyoto and spontaneously hypertensive rats.
Our previous studies have shown that ethanol attenuates baroreflex function in Wistar-Kyoto (WKY) but not in spontaneously hypertensive rats (SHRs). The present study determined the effects of chronic ethanol administration on alpha(2)-binding sites in brainstem areas that modulate baroreflexes. In vitro autoradiography was utilized to evaluate the effect of a 3-month ethanol feeding on the density (B(max)) and affinity (K(D)) of alpha(2)-adrenoceptors in the middle (mNTS) and rostral (rNTS) portions of the nucleus tractus solitarius of SHRs and WKY rats. Autoradiographic examination of brainstem sections preincubated with [125I]p-iodoclonidine revealed no inter-strain differences in alpha(2)-binding in control rats. Ethanol feeding caused strain-dependent changes in alpha(2)-binding activity, which comprised significant (P<0.05) decreases in the density of alpha(2)-binding sites in both areas of the NTS in SHRs versus no effect in WKY rats. These findings do not favor a role for brainstem alpha(2)-adrenoceptors in ethanol-induced attenuation of baroreflexes. Interestingly, the ethanol-evoked reduction in the NTS alpha(2)-receptor density in SHRs may explain reported findings that ethanol abolishes the hypotensive effect of the alpha(2)-adrenoceptor agonist clonidine in this rat model.
El-Mas
M M
MM
Department of Pharmacology, School of Medicine, East Carolina University, Greenville, NC 27858-4353, USA.
Abdel-Rahman
A A
AA
D000818:Animals; D001345:Autoradiography; D001665:Binding Sites / Q000187:drug effects; D001933:Brain Stem / Q000378:metabolism*; D004334:Drug Administration Schedule; D000431:Ethanol / Q000008:administration & dosage* / Q000494:pharmacology; D006973:Hypertension / Q000378:metabolism*; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR / Q000378:metabolism*; D011921:Rats, Inbred WKY / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D012016:Reference Values; D017552:Solitary Nucleus / Q000378:metabolism; D013045:Species Specificity
D011942:Receptors, Adrenergic, alpha; D000431:Ethanol