Alteration of alpha and muscarinic receptors in rat brain and heart following chronic nicotine treatment.
Adrenergic and muscarinic binding sites in 4 brain regions (cerebral cortex, corpus striatum, hypothalamus/thalamus and brainstem) and in heart ventricles were measured in rats chronically treated with nicotine added to the drinking water in doses ranging from 6 to 8 mg/kg/day, for 4 weeks. Control rats received only tap water. The nicotine treatment led to increases in the specific binding of both [3H]prazosin and [3H]clonidine in the cerebral cortex. An increase in [3H]prazosin binding was also observed in the hypothalamus/thalamus of nicotine-treated rats. These changes were all due to an increase of about 23% in Bmax. In the brainstem and heart left ventricle, respectively, an increase and a decrease in the affinity of [3H]quinuclidinyl benzilate binding were observed. There were no changes of the binding parameters for the 3 radioligands in other regions tested, and no alteration of [3H]dihydroalprenolol binding was detected in any region examined. These results indicate that chronic administration of nicotine causes an increase in the density of alpha 1- and alpha 2-binding sites in some brain regions and reciprocal changes of the affinity of muscarinic binding sites in the brain and in the heart.
D000818:Animals; D001921:Brain / Q000378:metabolism*; D001933:Brain Stem / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D003000:Clonidine / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009538:Nicotine / Q000008:administration & dosage*; D011224:Prazosin / Q000378:metabolism; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D011976:Receptors, Muscarinic / Q000187:drug effects*; D013788:Thalamus / Q000378:metabolism; D013997:Time Factors
D011942:Receptors, Adrenergic, alpha; D011976:Receptors, Muscarinic; D011813:Quinuclidinyl Benzilate; D009538:Nicotine; D003000:Clonidine; D011224:Prazosin