Amino Acid Transmitters

Amino Acid Transmitters - Amino Acid Transmitters Storage o...

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Amino Acid Transmitters Storage o GABA is packaged and stored in vesicles in the presynaptic terminals, from which it is released into the synaptic cleft o Vesicular transporter has been identified that accumulates GABA – has 12 presumptive transmembrane domains and a very large cytoplasmic N terminus of approximately 130 amino acids – called GAT o Transporter is highly dependent on electrical potential across vesicular membrane o GAT has a lack of substrate specificity and will transport the inhibitory transmitter Gly as well as GABA Release and Reuptake o Arrival of action potential results in release of GABA into synaptic cleft o Reuptake is the primary way GABA is inactivated when released from neurons o All known GATs are expressed in both neurons and glia, but we don’t know why there are multiple transporters for GABA o KEY: GATs transporters are not uniquely concentrated in the plasma membrane of the presynaptic GABA terminals GABA Receptors o GABA receptors are found primarily in nerve cell membranes – most CNS neurons possess them, but also are expressed by astrocytes (involved in chloride channels), and also found outside the CNS on autonomic nervous system neurons o Two Major Types of GABA receptors: the inotropic and the metabotropic – they differ pharmacologically, but also in second-messenger mechanisms, differences in the location of these receptor subtypes in the mammalian CNS, and their molecular composition Autoreceptor Regulation of GABA Release o Regulation of GABA neurons takes place predominantly through metabotropic GABA receptors located on GABAergic nerve terminals
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This document was uploaded on 04/06/2011.

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Amino Acid Transmitters - Amino Acid Transmitters Storage o...

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