Anterior cerebellum as a site for morphine analgesia and post-stimulation analgesia

The microinjection of 10 micrograms Morphine into culmen region of anterior cerebellum produced profound analgesia in rats, and this was antagonised with intraperitoneal administration of naloxone. On the other hand, the same injection of morphine into lobus simplex and declive region of posterior cerebellum was without any effect on nociception. Further it was observed that chronic surgical ablation of culmen-centralis region of anterior cerebellum markedly diminished the duration of analgesia elicited with systemic administration of morphine, though ablation per se had no influence on nociception. Also, the focal electrical stimulation of culmen region for brief period exhibited post-stimulation analgesia. These findings indicate that anterior cerebellum specifically plays some role in the modulation of physiological mechanisms of pain relief.