Regional differences of L-type high voltage-gated calcium channel subunit expression in the mouse brain after chronic morphine treatment

As functional changes in L-type high voltage-gated calcium channels (HVCCs) are recognized to be one of the major neurochemical modifications occurring in brains of animals with morphine physical dependence, this study attempts to examine whether regional difference in the expressions of HVCC subunits are produced in the brains under such pathological conditions. Scatchard analysis of [(3)H]PN200-110 binding showed increased Bmax values in the cerebral cortex and the mesolimbic region including the nucleus accumbence, which are brain regions participating in the development of morphine physical dependence, but not in the cerebellum. In the former two brain regions, alpha1C and alpha1D subunits of L-type HVCCs and alpha2/delta1 subunit increased, although decreases of alpha1B and alpha2/delta1 subunits were observed in the cerebellum. A single dose of morphine did not change the expression of any of the HVCC subunits. These results indicate that the increased L-type HVCC subunits in the cerebral cortex and mesolimbic region participate in the development of morphine physical dependence.