GABA synaptic transmission

NT237 Radcliffe, K. A., J. L. Fisher, R. Gray, and J. A. Dani. Nicotinic modulation of glutamate and GABA synaptic transmission of hippocampal neurons. Ann NY Acad Sci 1999 868 591-610. 

There are numerous transmitter substances. They include the amino acids glutamate, GABA and glycine acetylcholine the monoamines dopamine, noradrenaline and serotonin the neuropeptides ATP and NO. Many neurones use not a single transmitter but two or even more, a phenomenon called cotransmission. Chemical synaptic transmission hence is diversified. The basic steps, however, are similar across all neurones, irrespective of their transmitter, with the exception of NO transmitter production and vesicular storage transmitter release postsynaptic receptor activation and transmitter inactivation. Figure 1 shows an overview. Nitrergic transmission, i.e. transmission by NO, differs from transmission by other transmitters and is not covered in this essay. 

GABAa receptors. Furthermore, applied GABA hyperpolarizes the post-synaptic neuron, and this response can be blocked reversibly by bicucul-line, indicating that bicuculline directly blocks the GABA receptors. Such GABAergic synaptic transmission is essential to the enhanced ability of the specialized AL PNs to follow intermittent pheromonal stimuli (77). 

Compound (58) has been shown to be sufficiently selective to be of use in microelectrophoretic investigations of GABA-mediated synaptic transmission... 

These amino acid transmitters are predominant, accounting for most of the fast synaptic transmission in the brain. Together they occur in 70-80% of cerebral neurons. The concentration of GABA is for example up to 1000 times greater than that of other transmitters like acetylcholine or dopamine. 

The functional significance of this drug-receptor interaction is that the receptor complex regulates the entrance of chloride into the postsynaptic cells. The increase in chloride conductance mediated by GABA is intensified by the benzodiazepines. This facilitation of GABA-induced chloride conductance results in greater hyperpolarization of these cells and therefore leads to diminished synaptic transmission. 

GABA-A receptors. In G. Biggio, E. Costa (Eds.). GABAergic Synaptic Transmission. New York Raven. 

In the past decade, considerable evidence has accumulated that a primary molecular target of general anesthetics is the GABA receptor-chloride channel, a major mediator of inhibitory synaptic transmission. Inhaled anesthetics,... 

Moldavan MG, Irwin RP, Allen CN (2006) Presynaptic GABA(B) receptors regulate retinohy-pothalamic tract synaptic transmission by inhibiting voltage-gated Ca2+ channels. J Neurophysiol 95 3727 41... 

Wu SY, Wang MY, Dun NJ (1991) Serotonin via presynaptic 5-HTi receptors attenuates synaptic transmission to immature rat motoneurons in vitro. Brain Res 554 111-21 Yamamoto Y, Mochizuki T, Okakura-Mochizuki K, Uno A, Yamatodani A (1997) Thioperamide, a histamine H3 receptor antagonist, increases GABA release from the rat hypothalamus. Methods Find Exp Clin Pharmacol 19 289-98... 

Cunha RA, Sebastiao AM, Ribeiro JA (1998) Inhibition by ATP of hippocampal synaptic transmission requires localized extracellular catabolism by ecto-nucleotidases into adenosine and channelling to adenosine Ai receptors. J Neurosci 18 1987-95 Cunha RA, Ribeiro JA (2000a) Purinergic modulation of [3H]GABA release from rat hippocampal nerve terminals. Neuropharmacology 39 1156-67 Cunha RA, Ribeiro JA (2000b) Adenosine A2a receptor facilitation of synaptic transmission in the CA1 area of the rat hippocampus requires protein kinase C but not protein kinase A activation. Neurosci Lett 289 127-30... 

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