PROLONGED INCUBATION WITH NEUROPEPTIDE-Y UP-REGULATES BETA-ADRENOCEPTORS YET DOES NOT CAUSE SUPERSENSITIVITY OF BETA-ADRENOCEPTOR SIGNALING

In neonatal rat ventricular myocytes prolonged incubation with 1 mu M neuropeptide Y (2 h-48 h) increased beta-adrenoceptor density 16-24% (n = 4-8, all p < 0.05), an effect prevented by pertussis toxin pretreatment. Prolonged incubation with neuropeptide Y had no effect on adenylylcyclase activity stimulated by 5'-guanylylimidodiphosphate or (-)-isoprenaline, probably because of a neuropeptide Y-induced decrease in affinity of the beta-adrenoceptor for agonist. Thus, chronic incubation with an inhibitory agonist does not inevitably lead to supersensitivity of the adenylylcyclase pathway.