Isradipine is able to separate morphine-induced analgesia and place conditioning

The effect of isradipine, a dihydropyridine calcium antagonist, on morphine-induced place preference and analgesia in rats and mice was studied. Isradipine (0.6-5.0 mg/kg s.c.) inhibited an acquisition of morphine-induced place preference in rats and mice in a dose-related manner. Isradipine did not affect or strengthen morphine-induced analgesia as measured by tail-clip and hot-plate tests in mice and tail-clip and tail-flick tests in rats. The results suggest that analgesic and reinforcing effects of morphine might be pharmacologically separated by isradipine.