An<unk>  <unk>  is a kind of synaptic potential that makes a<unk>  neuron less likely to generate an action potential.<unk>  were first investigated in motorneurons by David P. C. Lloyd, John Eccles and Rodolfo Llinás in the 1950s and 1960s. The opposite of an<unk>  is an excitatory<unk>  potential (EPSP), which is a synaptic potential that makes a<unk>  neuron more likely to generate an action potential.<unk> s can take place at all chemical synapses, which use the secretion of neurotransmitters to create cell to cell signalling.<unk>  presynaptic neurons release neurotransmitters that then bind to the<unk>  receptors; this induces a change in the permeability of the<unk>  neuronal membrane to particular ions. An electric current that changes the<unk>  membrane potential to create a more negative<unk>  potential is generated, i.e. the<unk>  membrane potential becomes more negative than the resting membrane potential, and this is called hyperpolarisation. To generate an action potential, the<unk>  membrane must depolarize—the membrane potential must reach a voltage threshold more positive than the resting membrane potential. Therefore, hyperpolarisation of the<unk>  membrane makes it less likely for depolarisation to sufficiently occur to generate an action potential in the<unk>  neurone. Depolarization can also occur due to an<unk>  if the reverse potential is between the resting threshold and the action potential threshold. Another way to look at<unk> s is that they are also a chloride conductance change in the neuronal cell because it decreases the driving force. This is because, if the neurotransmitter released into the synaptic cleft causes an increase in the permeability of the<unk>  membrane to chloride ions by binding to ligand-gated chloride ion channels and causing them to open, then chloride ions, which are in greater concentration in the synaptic cleft, diffuse into the<unk>  neuron. As these are negatively charged ions, hyperpolarisation results, making it less likely for an action potential to be generated in the<unk>  neuron. Microelectrodes can be used to measure<unk>  potentials at either excitatory or<unk>  synapses. In general, a<unk>  potential is dependent on the type and combination of receptor channel, reverse potential of the<unk>  potential, action potential threshold voltage, ionic permeability of the ion channel, as well as the concentrations of the ions in and out of the cell; this determines if it is excitatory or<unk> .<unk> s always want to keep the membrane potential more negative than the action potential threshold and can be seen as a "transient hyperpolarization". EPSPs and<unk> s compete with each other at numerous synapses of a neuron. This determines whether or not the action potential at the presynaptic terminal regenerates at the<unk>  membrane. Some common neurotransmitters involved in<unk> s are GABA and glycine. Flowchart describing how an<unk>  works from neurotransmitter release to summation
Inhibitory postsynaptic potential
Presynaptic inhibition
Spike-timing-dependent plasticity
Synaptic gating
Excitatory synapse
End-plate potential
Depolarization-induced suppression of inhibition
Mechanosensitive channels