Chapter 9 Physiology of transmission at a giant glutamatergic synapse in cerebellum

Abstract

Publisher Summary The majority of excitatory synaptic pathways within the cerebellum utilize glutamate as the neurotransmitter. The three principal glutamatergic synapses in cerebellum are those formed between climbing fibers and Purkinje cells, mossy fibers and their targets within the granular layer, and parallel fibers and their targets within the molecular layer. The unipolar brush cells (UBCs) are found in the dorsal cochlear nucleus—a center that is innervated by primary auditory fibers and receives many other non-auditory inputs. The UBC receives innervation from glutamatergic afferent fibers, and both the synaptic ultrastructure and physiology of transmission are unique in the central nervous system. This chapter discusses the recent data concerning the physiology of transmission at this novel glutamatergic synapse. The ultrastructure of the MF–UBC synapse is unique among glutamatergic synapses, for at all other glutamatergic synapses studied to date, the release sites are generally apposed to discrete areas of post-synaptic density in which ionotropic receptors are concentrated, but between which the density of ionotropic receptors in the areas of neuronal membrane is low. The synaptic currents evoked in UBCs by stimulation of mossy fiber afferents have been studied using patch-clamp recording methods in thin slices of rat cerebellar vermis.