Slow synaptic transmission in the central nervous system

Abstract

New types of nicotinic connections with much slower kinetics than previously described have recently been discovered in several regions of the central nervous system (CNS). Slow nicotinic responses have been reported in the interpeduncular nucleus, hippocampus, neocortex, striatum, spinal cord, and thalamus. Studies have suggested that α4β2 containing nicotinic receptors may be the receptor subtype mediating the slow nicotinic synaptic events. These slow nicotinic excitatory postsynaptic potentials (EPSPs) appear to be the predominant nicotinic synaptic event in regions of the CNS (hippocampus and neocortex) that previously were thought to be dominated by α7 nicotinic receptors. Depending on the region of the CNS, slow nicotinic events may be mediated by classical synaptic transmission or volume transmission. Although the slow nicotinic EPSPs may vary subtly in kinetics and possible mechanisms of transmission, all known neuronal types that respond with slow nicotinic EPSPs are inhibitory. Thus slow nicotinic EPSPs may play an important role in controlling local and global network function through feedforward and feedback inhibition.