Calcium in the Nerve Cell

Abstract

During the last decade, the study of Ca²⁺ -regulated functions has expanded explosively: Ca²⁺ is now regarded as the triggering agent of many biological reactions and has attained the status of a second messenger.^1,2 The functions of Ca²⁺ in the nervous system are many. At the cell surface, Ca²⁺ alters the membrane stability and permeability^3–5 and is involved in nerve impulse propagation.^4,6–8 On stimulation, there is an increased influx of Ca²⁺ into the nerve cell which couples excitation to neurotransmitter release.^4,9–11 The actions of the neurotransmitters on the postsynaptic membrane may also involve Ca²⁺ in the sequence of events that leads to the response of the postsynaptic cell.¹² It is is now recognized that Ca²⁺ regulates the activity of enzymes such as adenylate cyclase,^13–15 phosphodiesterase,^14,15 protein kinases,^12,16–18 Ca²⁺ - ATPases,^19,20 and tyrosine hydroxylase,²¹ among others. Furthermore, the action of narcotic drugs in the nervous system is mediated by alterations in the Ca²⁺ content of the nerve cell,^22–26 and the action of local anesthetics occurs through the displacement of Ca²⁺. ^5,27