Transmitter cosynthesis by corticopetal basal forebrain neurons

The objective was to determine if corticopetal basal forebrain neurons could co-synthesize different transmitters. Histochemical labeling of a molecular marker of connectivity (wheat germ agglutinin lectin-bound horseradish peroxidase [HRP]; axonal uptake and retrograde transport from neocortex) and immunohistochemical labeling of molecular markers of transmitter synthesis (glutamic acid decarboxylase [GAD]: choline acetyltransferase [ChAT]) were combined in adult cats and examined by light microscopy. Adjoining partial profiles of the same neurons in the basal forebrain co-localized GAD + HRP and ChAT + HRP in adjacent faces of serial tissue sections. GAD + ChAT were also co-localized within individual profiles of neurons in the basal forebrain from single tissue sections. The results indicate that infrequent corticopetal neurons in the basal forebrain can produce both gamma-aminobutyric acid and acetylcholine.