Inhibitory postsynaptic potential

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Inhibitory postsynaptic potential (IPSP) is a form of graded potential that occurs at the post-synaptic neurone.  The type of channel coupled to a receptor, the concentration of the ions inside and outside of the cell and more importantly, the reversal potential of the post-synaptic potential in relation to the threshold voltage all determine if an Inhibitory postsynaptic potential (IPSP) results[1].  Neurotransmitters such as GABA (Gamma-AminoButyric Acid) and glycine are responsible for IPSP.  For example, if a neurotransmitter uses GABA, the GABA receptor on the post-synaptic memebrane would be activated and therefore, open and become selectively permeable to Cl-. Chloride ions therefore, flow into the cell and K ions flow out of the cell, making the inside of the cell more negative.  Hence, the cell becomes hyperpolarised [2].  Once this is the case, then the threshold level is not reached and so an action potential cannot be generated. Both glycine and GABA act as inhibitory neurotransmitter in the retina of most vertebrate including humans[3].

For further notes on Excitable cells, please use the following links:


  1. NCBI (2001), Available at: Last accessed: 22/11/2011
  2. Albert, B. et al (2008), Molecular Biology of the Cell, 5th edition, Abingdon UK, Garland Science.
  3. Organisation of the Retina and Vision System (2011) Available at: Last Accessed: 22/11/2011.
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