Chronic treatment with nifedipine does not change the number of [3H]nitrendipine and [3H]dihydroalprenolol binding sites.
Possible receptor changes occurring after withdrawal of chronic nifedipine treatment or chronic propranolol treatment were examined by administering nifedipine (100 mg/kg per day) or propranolol (45 mg/kg per day) to rats for 2 weeks and then withdrawing treatment [3H]Nitrendipine and [3H]DHA binding were measured in membrane fragments of the ventricle. In propranolol-treated rats, 8 h after the last administration, the maximum binding for [3H]DHA was significantly increased from 79.9 +/- 8.0 to 139.8 +/- 12.8 fmol/mg protein (mean +/- S.E.); the dissociation constant was significantly increased from 4.9 +/- 0.7 to 10.7 +/- 1.2 nM. On the other hand, in nifedipine-treated rats, 12 and 48 h after the last administration, [3H]nitrendipine binding and [3H]DHA binding had not changed significantly. These results indicate that the mechanism of the calcium antagonist withdrawal syndrome may be different from that of beta-blocker withdrawal syndrome.
D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D015220:Calcium Channels; D008297:Male; D009543:Nifedipine / Q000008:administration & dosage / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism*
D015220:Calcium Channels; D011943:Receptors, Adrenergic, beta; D011978:Receptors, Nicotinic; C028413:dihydroalprenolol receptor; D011433:Propranolol; D009543:Nifedipine