GABA(A) RECEPTORS CONTROL THE EXCITABILITY OF NEURONAL POPULATIONS

This chapter focuses on the role of GABAA receptor function in the collective behavior of cortical neuronal populations, primarily in the hippocampal formation. Experimental accessibility, plasticity, and a prominent role in learning and memory account for numerous anatomical, biochemical, and physiological studies in this brain region. GABA-mediated inhibition occurs through two physiological mechanisms: An increase in membrane conductance and a hyperpolarization of the postsynaptic membrane. The combination of features of GABAergic inhibition, the distribution and widespread dendritic arborization of GABAergic interneurons, the ubiquitous subcellular distribution of GABAA and GABAB receptors, the concentration of GABAA receptors at strategically pivotal sites close to the cell soma, the large chloride conductance increases produced by shunting inhibition, and the generation of spontaneous IPSPs indicate a very powerful inhibitory control of a given cell population in the mammalian cortex. Under physiological conditions, the state of excitability of a cortical neuronal population represents a finely tuned balance between excitation and inhibition. Slight alterations of the efficacy of inhibition may lead to greater changes in the collective behavior of a population of cells. © 1992, Academic Press, Inc.