GABAB Receptor-Mediated Inhibition of Synaptic Transmission in the Hippocampus: Pharmacology and Intracellular Mechanisms
Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the central nervous system that affects cellular excitability by opening or closing a variety of ion channels or by modulating a number of intracellular messengers. Some actions of GABA are associated with an increase in membrane conductance to Cl- ions and are antagonized by the GABA antagonists bicuculline and Picrotoxin. Receptors mediating these effects are referred to as GABAA receptors and have been investigated intensively, especially because of their close association to the benzodiazepine and barbiturate binding sites. More recently, presynaptic bicuculline-insensitive actions of GABA have been discovered by Bowery and his colleagues, who opened up a new field of investigation (see Bowery, 1982). These actions are mediated by GABAB receptors, which are specifically activated by the GABAB agonists baclofen and 3-aminopropylphosphonic acid. We describe in this chapter recent data concerning the presynaptic actions mediated by GABAB receptors in the hippocampus. We first briefly summarize the better known postsynaptic effects of GABAB receptor activation.
KeywordsPertussis Toxin GABAB Receptor Stratum Radiatum Presynaptic Action Inhibitory Postsynaptic Potential
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