Calcium-dependent GABA release from brain slices of morphinized mice

Acute morphine administration had no effect on the spontaneous release of (³H)-GABA and the Ca²⁺-dependent release from mouse striatum and cerebellum. No effect on (³H)-GABA release also was detected in the morphine tolerant and the 24 hours morphine abrupt withdrawal animals. However, Ca²⁺-dependent (³H)-GABA release from striatal slices was significantly increased in the morphine 72 hr abrupt withdrawal mice. The increase of the release was dependent on Ca²⁺ concentration in the medium. Naloxone enhanced (³H)-GABA release from striatum in morphine tolerant mice. However, (³H)-GABA release from cerebellum did not change by any morphine treatment. These results suggest that striatal GABAergic neurons participate in morphine withdrawal.