Abstract
Effects of morphine hydrochloride on the cerebellum were examined in cats. Morphine (2.0 mg/kg, i.v.) decreased the potentials by superficial radial nerve (SR), nucleus reticularis lateralis (LRN), or nucleus olivaris inferior (ION) stimulation on the cerebellar cortices. These effects were antagonized by naloxone hydrochloride (0.4 mg/kg, i.v.). In the LRN or ION, morphine decreased the potentials evoked by SR stimulation. In the LRN- or ION-lesioned cat, morphine decreased the potentials evoked by SR stimulation on the cerebellar cortices. This opiate decreased the potentials evoked by tooth pulp stimulation on the vermis, and this effect was also antagonized by naloxone. Morphine slightly decreased the potentials evoked by SSA-I stimulation on the cerebellar cortices. Furthermore, the potentials evoked by SR stimulation on the SSA-I were slightly decreased by morphine. These results may suggest that the cerebellum plays an important role in not only the motor system, but also the sensation of pain.
