Galanin-containing fibers innervate substance P-containing neurons in the pedunculopontine tegmental nucleus in humans

Galanin is a putative peptide transmitter distributed widely in the central nervous system. Galanin shows potent inhibitory effects on neuronal activity and learning behaviors induced or mediated by acetylcholine. Here, we demonstrate that in humans there are abundant galanin-containing fibers in the pedunculopontine tegmental nucleus, the lateral dorsal tegmental nucleus and the oral pontine reticular nucleus. These neurons contain both acetylcholine and substance P (SP). Using a double-immunostaining method, we show that galanin-containing terminals form pericellular baskets around many SP-positive neurons in these nuclei. Our results suggest galanin may influence brain functions via inputs to the ascending mesopontine acetylcholine-containing nuclei.