There are different types of neurotransmitters. For example, glutamate (glu) is involved in the excitation of the central nervous system (CNS). Aspartate (asp) is involved in the excitation of the brain and spinal cord. Gama-aminobutyric acid (GABA) is involved in the inhibition of the CNS. Glycine (gly) is involved in the inhibition in the spinal cord. In addition, acetylcholine (ACh) is involved in attention and autonomic activation. Dopamine (DA) is involved in movement and reward. Serotonin (5-HT) is involved in mood control, sensory processing, and relaxation.
The neurotransmitter noradrenaline (NA) is also known as norepinephrine (NE), and is involved in the control of smooth muscles and arousal. Substance P (SP) is involved in many functions including the signaling of pain. Opioids (Enk) are also involved in the regulation of pain, as well as satiety. Neuropeptide Y (NPY) is involved in the control of appetite. Adenosine triphosphate (ATP) is important for various functions.
The release of neurotransmitters can have ionotropic and/or metabotropic effects on the post-synaptic cell. The ionotropic effect means that upon activation the receptor can let the ions across the membrane. The metabotropic effect means that upon activation the receptor can stimulate biochemical signaling internally. A synapse can have both types of receptors, and some receptors have both functions. Metabotropic receptors may influence the gene expression and protein production, as well as the oscillating cycles of enzyme activities.
Ionotropic receptors associated with sodium channels will enable a neuron to fire. Those receptors associated with chloride channels may inhibit the firing to set the membrane potential back to the resting state. Post-synaptic potentials are the ultimate alterations in the membrane potentials, which can be excitatory (EPSP) or inhibitory (IPSP). Various synapses may have competing effects by reinforcing or opposing each other’s influences. The synaptic influences may be affected by the distance between a synapse and the axon hillock, as well as the thickness and shape of the dendrites.