Effects of opiates on cAMP in homogenates and slices of rat striata

In slices of rat striata, incubated in a depolarizing medium (53 mM K+), morphine decreased by concentration of cAMP even in concentrations as low as 0.5 micron. This effect was inhibited by naloxone. Levorphanol, but not dextrorphan, induced a similar effect as morphine. In tissue, homogenized in a hypotonic medium, morphine (5-50 micron) also slightly decreased the concentration of cAMP, which was antagonized by naloxone. Neigher slices nor homogenates of morphine-withdrawn rats showed any alteration in the concentration of cAMP.