ALTERATIONS IN CEREBRAL CORTICAL GALANIN CONCENTRATIONS FOLLOWING NEUROTRANSMITTER-SPECIFIC SUBCORTICAL LESIONS IN THE RAT

Galanin is associated with multiple projection neurons, and its immuno reactivity in the cerebral cortex may be derived from diverse sources. We investigated the effects of subcortical lesions on cerebral cortic al galanin concentrations. Lesions of the anterior noradrenergic bundl e (ANB) comparably reduced cerebral cortical galanin and norepinephrin e (NE) concentrations. The effects of the ANB lesions on galanin were immediate and became most pronounced 1 week later. Extensive unilatera l lesions of the nucleus basalis of Meynert (NBM) decreased galanin co ncentrations, although not as markedly as after ANB lesions. The NBM l esions had no additional effect in the presence of an ANB lesion. Decr eases in cerebral cortical galanin concentrations depended upon the ex tent and the duration of the NBM lesion and were not as pronounced as the decreases in markers of cholinergic activity. Acute treatments wit h physostigmine, which inhibit cerebral cortical AChE, had no effect o n galanin concentrations. The depletion of galanin following an NBM le sion was most pronounced within hours of the insult, while the depleti on of ChAT following the same lesions required several days to develop . Cortical concentrations of galanin and 5-HT increased 1 hr after dor sal raphe nucleus (DRN) lesions and then decreased 7 d later. Six week s later, galanin concentrations recovered in the cerebral cortex despi te the continued depletion of 5-HT. These studies suggest that a subst antial portion of cerebral cortical galanin may derive from noradrener gic neurons and may be modulated by cortically-projecting ACh and 5-HT neurons.