Secretin facilitates GABA transmission in the cerebellum

Secretin was the first hormone discovered in human history, and yet, its fu nction as a neuropeptide has been overlooked in the past. The recent discov ery of the potential use of secretin in treating autistic patients, togethe r with the conflicting reports on its effectiveness, urges an in-depth inve stigation of this issue. We show here that in the rat cerebellar cortex, mR NAs encoding secretin are localized in the Purkinje cells, whereas those of its receptor are found in both Purkinje cells and GABAergic interneurons. Immunoreactivity for secretin is localized in the soma and dendrites of Pur kinje cells. In addition, secretin facilitates evoked, spontaneous, and min iature IPSCs recorded from Purkinje cells. We propose that secretin is rele ased from the somatodendritic region of Purkinje cells and serves as a retr ograde messenger modulating GABAergic afferent activity.