Effect of chronic nicotine treatment against repeated immobilization stress.
Alpha 2 and beta adrenoceptors, and muscarinic cholinoceptors in 2 brain regions (cerebral cortex and hippocampus) were measured in rats which received either tap water or nicotine added to the drinking water (5-8 mg/kg/day) for 4 weeks, and immobilization stress (daily 2 hr) for the last 5 days. The repeated stress induced a reduction in the maximum number of binding sites (Bmax) for (3H)dihydroalprenolol (DHA) in the cerebral cortex of rats with tap water, without affecting (3H)clonidine binding. Nicotine-treatment also caused a decrease in the Bmax of cortical (3H)DHA binding comparable to the case of stress, and increased the (3H)clonidine binding. However, the combination of nicotine- and stress-treatments failed to induce further no changes in the 2 radioligands binding. The binding of (3H)quinuclidinyl benzilate in the cerebral cortex and of the 3 radioligands in the hippocampus was unaltered by nicotine- and/or stress-treatments. These results indicate that long-term administration of nicotine induces down-regulation of cortical beta adrenoceptors and seemingly attenuates the receptor alteration by repeated stress.
D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D003000:Clonidine / Q000378:metabolism; D004082:Dihydroalprenolol / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009538:Nicotine / Q000494:pharmacology*; D009928:Organ Specificity; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D012149:Restraint, Physical; D013315:Stress, Psychological / Q000378:metabolism*
D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D011976:Receptors, Muscarinic; D004082:Dihydroalprenolol; D011813:Quinuclidinyl Benzilate; D009538:Nicotine; D003000:Clonidine