Serotonin and GABA-Induced Fluctuations in Extracellular Ion Concentration in the Hippocampal Slice

Abstract

In central grey matter, activity-related release of K⁺ from neurons can result in considerable K⁺ accumulation in the extracellular space. It is likely that synaptic currents contribute to these rises in extracellular K⁺ concentration ([K⁺]_o). However, this contribution cannot be readily distinguished under conditions of neuronal excitation and associated high K⁺ conductance.Increases in [K⁺]_o have been observed near medullary respiratory neurons during synaptic inhibition (Richter et al.,1978), and have also been noted following application of γ-aminobutyric acid (GABA) in cerebral cortex (Brinley et al., 1960) and spinal cord (Kudo and Fukuda, 1976). In the present investigation, we have studied the effects of two putative inhibitory neurotransmitters, serotonin (5HT) and GABA, on [K⁺]_o in the rat hippocampal slice preparation.