<P> This system IPSPs can be temporally summed with subthreshold or suprathreshold EPSPs to reduce the amplitude of the resultant postsynaptic potential . Equivalent EPSPs (positive) and IPSPs (negative) can cancel each other out when summed . The balance between EPSPs and IPSPs is very important in the integration of electrical information produced by inhibitory and excitatory synapses . </P> <P> The size of the neuron can also affect the inhibitory postsynaptic potential . Simple temporal summation of postsynaptic potentials occurs in smaller neurons, whereas in larger neurons larger numbers of synapses and ionotropic receptors as well as a longer distance from the synapse to the soma enables the prolongation of interactions between neurons . </P> <P> GABA is a very common neurotransmitter used in IPSPs in the adult mammalian brain and retina . GABA receptors are pentamers most commonly composed of three different subunits (α, β, γ), although several other subunits (δ, ε, θ, π, ρ) and conformations exist . The open channels are selectively permeable to chloride or potassium ions (depending on the type of receptor) and allow these ions to pass through the membrane . If the electrochemical potential of the ion is more negative than that of the action potential threshold then the resultant conductance change that occurs due to the binding of GABA to its receptors keeps the postsynaptic potential more negative than the threshold and decreases the probability of the postsynaptic neuron completing an action potential . Glycine molecules and receptors work much in the same way in the spinal cord, brain, and retina . </P> <P> There are two types of inhibitory receptors: </P>

Ionic basis of excitatory and inhibitory post-synaptic potentials