BASAL FOREBRAIN LESIONS WITH OR WITHOUT RESERPINE INJECTION INHIBIT CORTICAL REORGANIZATION IN RAT HINDPAW PRIMARY SOMATOSENSORY CORTEX FOLLOWING SCIATIC-NERVE SECTION

To test the hypothesis that cortical reorganization depends on acetylcholine and one or more of the monoamines, the hindpaw cortex was mapped in eight different groups of mature rats: (1) untreated; (2) after sciatic nerve transection; (3) after intraperitoneal injections of reserpine, to reduce the level of cortical monoamines; (4) after ibotenic acid lesion of the nucleus basalis of Meynert (NBM), to destroy cholinergic cells projecting to the cortex; (5) after reserpine treatment and transection; (6) after ibotenic acid lesion and transection; (7) after reserpine treatment and ibotenic acid lesion; and (8) after reserpine treatment, ibotenic acid lesion, and transection. Four days after transection, the cortex had reorganized in the transected group. However, this process of reorganization was prevented in transected animals with NBM lesions. Treatment with reserpine alone did not inhibit the process of reorganization, nor did it enhance the effect of NBM lesion. Nonetheless, the animals treated with reserpine and transected had higher response thresholds in the reorganized cortex than did the animals that were treated but not transected. These data suggest that acetylcholine plays an important role in the early reorganization that follows deafferentation, and that one or more of the monoamines may have other influences on reorganization of the primary somatosensory cortex of adult rats.