Introduction

Approximately 30% of neurons in the brain produce GABA, and almost every neuron can respond to GABA. Some nonneural cells also make GABA, including the cells of the endocrine pancreas and the reproductive tracts. GABA in the pancreas presumably acts as a signaling molecule, in a similar manner to CNS signaling. GABA function in the reproductive tracts is unknown.

Encyclopedia of the Human Brain Volume 2

Copyright 2002, Elsevier Science (USA).

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The molecules associated with GABA synthesis, degradation, transport, and signaling include two synthesizing enzymes, one degrading enzyme, two transporting proteins, and two classes of receptors. These molecules, their functions, and their putative locations are listed in Table I and illustrated in Fig. 1.

GABA acts by binding to GABA receptors, which are located on both pre- and postsynaptic cells. Generally, GABA receptor binding hyperpolarizes the cell, producing an inhibitory effect. In some circumstances, however, GABA can exert excitatory effects by depolarizing the membrane. Excitatory GABA effects occur most notably during development but also in the rodent suprachiasmatic nucleus, where it may be related to circadian rhythms.

Table I

GABA-Related Proteins, Their Locations, and Their Functions0

Table I

GABA-Related Proteins, Their Locations, and Their Functions0

Protein

Location

Function

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