THE MORMYRID ELECTROSENSORY LOBE IN-VITRO - PHYSIOLOGY AND PHARMACOLOGY OF CELLS AND CIRCUITS

This paper is concerned with the electrosensory lobe (ELL) of mormyrid electric fish as examined in in vitro slices. Intracellular recording s from morphologically identified cells and field potential recordings were used to characterize the physiology and pharmacology of ELL cell s. Most intracellular recordings were from the Purkinje-like interneur ons that are known as medium ganglion cells and from the two types of efferent neurons, large ganglion and large fusiform cells. Stimulation of primary afferent fibers elicits both excitatory and inhibitory eff ects in these cells, with the excitatory effects being mediated by bot h the AMPA and NMDA types of glutamate receptors and the inhibitory ef fects being mediated by both GABA(A) and glycine receptors. Parallel-f iber stimulation evokes an EPSP-IPSP sequence, with the EPSPs being me diated by both AMPA and NMDA receptors and the IPSPs being mediated by GABA(A) receptors only. The parallel fiber-evoked EPSPs and IPSPs sho w marked paired-pulse facilitation. A large and unusually broad spike is recorded inside medium ganglion cells, and field potential response s suggest that this spike is propagated into the apical dendrites. The results provide essential information for understanding how periphera l and central inputs are integrated in ELL.