Askew W E, Charalampous K D
Experientia. 1976 Nov 15;32(11):1454-6. doi: 10.1007/BF01937430.
An increase in mouse cerebellar C-GMP levels during acute morphine treatment was observed, which was possibly related to the decrease in C-GMP phosphodiesterase levels also observed in acute treatment. Chronic treatment lowered C-GMP levels as did abrupt withdrawal without naloxone.