DOWN-REGULATION OF PHOSPHOLIPASE C-BETA(1) FOLLOWING CHRONIC MUSCARINIC RECEPTOR ACTIVATION

To determine whether prolonged activation of a phospholipase C-coupled receptor can lead to a down-regulation of its effector enzyme, SH-SY5 Y neuroblastoma cells were incubated for 24 h with the muscarinic rece ptor agonist, oxotremorine-M. Under these conditions, significant redu ctions (46-53%) in muscarinic cholinergic receptor density, G(alpha q/ 11) and phospholipase C-beta(1) (but not the beta(3)-or gamma(1) isofo rms) were observed. These results suggest that a selective down-regula tion of phospholipase C-beta(1) may play a role in adaptation to chron ic muscarinic receptor activation. (C) 1998 Elsevier Science B.V.