Influx of which of the following ion is responsible for IPSP (inhibitory postsynaptic potential): March 2005

Ans. B: Chloride ion Sodium ion Despite their name, some neurotransmitters inhibit the transmission of nerve impulses. They do this by opening Chloride channels and/or Potassium channels in the plasma membrane. In each case, opening of the channels increases the membrane potential by Letting negatively-charged chloride ions (C1") in and Positively-charged potassium ions (K+) out This hyperpolarization is called an inhibitory postsynaptic potential (IPSP). Although the threshold voltage of the cell is unchanged, it now requires a stronger excitatory stimulus to reach threshold. Example: Gamma amino butyric acid (GABA). This neurotransmitter is found in the brain and inhibits nerve transmission by both mechanisms: Binding to GABAA receptors opens chloride channels in the neuron. Binding to GABAB receptors opens potassium channels.