RESUMEN
This study investigated the influence of diazepam on the binding characteristics of adrenoceptor, muscarinic and benzodiazepine receptors in rat parotid gland membrane using a radioligand binding assay. At a concentration of >10(-6)M, diazepam competed with [(3)H]dihydroalprenolol for ß-adrenoceptor, but not [(3)H]prazosin for α-adrenoceptor or [(3)H]quinuclidinyl benzilate for muscarinic receptor. Continuous administration of diazepam at doses of 0.4mg/kg/day, i.p. for 7days in rat significantly decreased pilocarpine (4.0mg/kg, i.p.)-induced parotid salivary flow. Diazepam also produced a significant increase in the dissociation constant (Kd) value for [(3)H]dihydroalprenolol binding, but no change in the maximal binding capacity (Bmax) value, and a decrease in the Kd value for [(3)H]diazepam binding to benzodiazepine receptors, but no change in the Kd or Bmax values for [(3)H]prazosin or [(3)H]quinuclidinyl benzilate binding. These results suggest that continuous administration of diazepam modifies affinity for ß-adrenoceptor and benzodiazepine receptor binding sites in parotid gland membrane and that changes in these binding sites may be closely related to diazepam-induced suppression of salivary secretion.