The Inhibitory Mechanism in the Frog Cerebellar Cortex

Abstract

1) A controversial problem on the inhibitory mechanism in the frog cerebellar cortex was brought to a conclusion by studying cortical field potentials generated by double and combined stimulation of the parallel fiber (Loc) and the white matter (WM). 2) Depth profiles of the field potentials elicited by Loc and WM stimulations were essentially similar to those found in other vertebrates. 3) The field potentials representing antidromic and orthodromic activations of Purkinje cells were inhibited for a period of 100-400 msec by conditioning Loc stimulation. The same was observed by conditioning WM stimulation which was made intense to involve activation of the mossy fiber-granule cell system and climbing fibers. 4) The field potentials of granule cell discharges elicited by WM stimulation were also suppressed for a period of 200-400 msec by conditioning Loc stimulation. 5) It is concluded that two inhibitory mechanisms operate in the frog cerebellar cortex: stellate cell inhibition of Purkinje cells and Golgi cell inhibition of granule cells.