Correlation between acetylcholine release and recovery of conditioned taste aversion induced by fetal neocortex grafts.

Rats with lesions of the gustatory neocortex (GN) show deficits in the acquisition of taste aversion. Fetal GN grafts to a lesioned animal restore taste aversion learning and establish connections with the host brain. In this work, we examined whether the grafts are biochemically functional and whether this fact can be related to behavioral recovery. Gustatory or occipital cortices from rat fetuses were transplanted to GN-lesioned rats. Two months later, taste aversion recovery was tested and the release of labeled gamma-aminobutyric acid (GABA), acetylcholine (ACh), dopamine and glutamate from the grafted tissue was assayed. Fetal GN grafts promoted recovery of learning and released GABA, ACh and glutamate in response to K+ depolarization. Occipital cortex grafts did not induce behavioral recovery, although they were capable of releasing GABA. In contrast, these grafts did not release ACh. Moreover, GN-grafted rats in which behavioral recovery was not seen also failed to release ACh. These results are in agreement with previous findings that cholinergic transmission is important in the GN and suggest that ACh may play a role in the graft-mediated behavioral recovery observed in this model.