Endogenous morphine and codeine Possible role as endogenous anticonvulsants

Exogenously administered morphine can have both convulsive or anticonvulsiv e effects, depending on the dose and species. The levels of the endogenous opiate alkaloids morphine and codeine were significantly elevated in specif ic rat brain regions by the convulsive drug, pentylenetetrazole, as well as by the anticonvulsant drugs, carbamazepine and phenytoin. Morphine and cod eine levels in peripheral tissues (heart, lung, spleen and adrenal) were un affected by these drugs. Maximal increases in morphine levels were seen in the hypothalamus and striatum (2-10-fold), while lesser increases occurred in the midbrain and brain stem (2-4-fold). Codeine levels were also markedl y increased in hypothalamus (5-10 fold), In contrast to morphine, codeine l evels were also increased in the hippocampus (2-10-fold), but were unchange d in the striatum. These studies suggest that the endogenous alkaloids morp hine and codeine are involved in the modulation of convulsions and that mor phine and/or codeine may act as an endogenous anticonvulsant. (C) 2001 Else vier Science BY. All rights reserved.