SIMULATED RESPONSES OF CEREBELLAR PURKINJE-CELLS ARE INDEPENDENT OF THE DENDRITIC LOCATION OF GRANULE CELL SYNAPTIC INPUTS

Cerebellar Purkinje cell responses to granule cell synaptic inputs wer e examined with a computer model including active dendritic conductanc es. Dendritic P-type Ca2+ channels amplified postsynaptic responses wh en the model was firing at a physiological rate. Small synchronous exc itatory inputs applied distally on the large dendritic tree resulted i n somatic responses of similar size to those generated by more proxima l inputs. In contrast, in a passive model the somatic postsynaptic pot entials to distal inputs were 76% smaller. The model predicts that the somatic firing response of Purkinje cells is relatively insensitive t o the exact dendritic location of synaptic inputs. We describe a mecha nism of Ca2+-mediated synaptic amplification, based on the subspiking threshold recruitment of P-type Ca2+ channels in the dendritic branche s surrounding the input site.