Corticotropin-releasing factor plays a permissive role in cerebellar long-term depression

This study of rat cerebellar slices yielded two lines of evidence indicatin g that the corticotropin-releasing factor (CRF) found in climbing fibers (C Fs) is critical for the induction of long-term depression (LTD) at the para llel fiber (PF) synapses of Purkinje cells (PCs) by their conjunctive activ ation with either stimulation of CFs or depolarization of PCs, First, LTD i nduction was effectively blocked by specific CRF receptor antagonists, alph a-helical CRF-(9-41) (alpha-h CRF) and astressin; and second, LTD was no lo nger observed in CF-deprived cerebella but was restored by CRF replenishmen t, The data obtained in this study suggest that these effects are mediated by protein kinase C (PKC) and not by Ca2+ signaling or cyclic GMP (cGMP) pr oduction.