The isolation and characterization of cDNAs encoding rat galanin and its precursor peptide reveal that rat galanin is synthesized initially as part of a 124-amino acid precursor that includes a signal peptide, galanin, and a 60-amino acid galanin mRNA-associated peptide. The neuropeptide galanin shows multiple inhibitory actions on neurotransmission and memory. In Alzheimer's disease, increased galanin-containing fibers hyperinnervate cholinergic neurons within the basal forebrain in association with a decline in cognition.