used for cell signaling and communication and can include ionotropic receptors and metabotropic receptors. These cell surface receptor types are differentiated by the mechanism and duration of action with ionotropic receptors being associated with fast signal transmission and metabotropic receptors being associated with slow signal transmission. Metabotropic receptors happen to cover a wide variety of cell-surface receptors with notably different signaling cascades. Ionotropic receptors Ionotropic receptors, otherwise known as ligand-gated ion channels, are fast acting receptors that mediate neural and physiological function by ion channel flow with ligand-binding. Nicotinic, GABA, and Glutamate receptors are among some of the cell surface receptors regulated by ligand-gated ion channel flow. GABA is the brain's main inhibitory neurotransmitter and glutamate is the brain's main excitatory neurotransmitter. GABA receptors GABAA and GABAC receptors are known to be ionotropic, while the GABAB receptor is metabotropic. GABAA receptors mediate fast inhibitory responses in the central nervous system (CNS) and are found on neurons, glial cells, and adrenal medulla cells. It is responsible for inducing Cl− ion influx into cells, thereby reducing the probability that membrane depolarization will occur upon the arrival of a graded potential or an action potential. GABA receptors can also interact with non-endogenous ligands to influence activity. For example, the compound diazepam (marketed as Valium) is an allosteric agonist which increases the affinity of the receptor for GABA. The increased physiological inhibitory effects resulting from increased GABA binding make diazepam a useful tranquilizer or anticonvulsant (antiepileptic drugs). On the other hand, GABA receptors can also be targeted by decreasing Cl− cellular influx with the effect of convulsants like picrotoxin. The antagonistic mechanism of action for this compound is not directly on the GABA receptor, but there are other compounds that are capable of allosteric inactivation, including T-butylbicyclophorothionate (TBPS) and pentylenetetrazole (PZT). Compared with GABAA, GABAC receptors have a higher affinity for GABA, they are likely to be longer-lasting in activity, and their responses are likely to be generated by lower GABA concentrations. Glutamate receptors Ionotropic glutamate receptors can include NMDA, AMPA, and kainate receptors. These receptors are named after agonists that facilitate glutamate activity. NMDA receptors are notable for their excitatory mechanisms to affect neuronal plasticity in learning and memory, as well as neuropathologies such as stroke and epilepsy. NDMA receptors have multiple binding sites just like ionotropic GABA receptors and can be influenced by co-agonists such the glycine neurotransmitter or phencyclidine (PCP). The