Neurotransmitter receptors are membrane proteins to which synaptic transmitters bind, leading to a physiological response in the postsynaptic cell. Neurotransmitter receptors can be ionotropic and cause a change in membrane conductance by an action on membrane channels or they can be metabotropic, causing activation of intracellular second messenger systems. Metabotropic receptors are often coupled to metabolic pathways through G proteins.

 Spinothalamic Tract Neurons, Role of Nitric Oxide