GABA B receptor

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GABA_B receptors (GABA_BR) are metabotropic transmembrane receptors that are linked via G-proteins to potassium channels (Chen et al., 2005). These receptors are found in the central and peripheral autonomic nervous system (Martin and Dunn, 2002). They can stimulate the opening of K⁺ channels which brings the neuron closer to the equilibrium potential of K⁺, hyperpolarising the neuron. This prevents sodium channels from opening, action potentials from firing, and VOCCs from opening, and so stops neurotransmitter release. Thus GABA_B receptors are considered inhibitory receptors.

GABA_B receptors can also reduce the activity of adenylyl cyclase and decrease the cell’s conductance to Ca²⁺ (Siegel et al., 1999; Martin and Dunn, 2002).

GABA_B receptors are involved in behavioral actions of ethanol [1], gamma-hydroxy butyric acid (GHB; "rape drug")[2], and possibly in pain [3]. Recent research suggests that these receptors may play an important developmental role [4].

GABA_BRs are similar in structure to and in the same receptor family with metabotropic glutamate receptors (MRC, 2003). There are two subtypes of the receptor, GABA_B1 and GABA_B2 (Purves et al., 2001; Martin and Dunn, 2002), and these appear to assemble as heterodimers in neuronal membranes by linking up by their intracellular C termini (Martin and Dunn, 2002; MRC, 2003). It is speculated that binding of GABA causes the subunits to swing shut around the agonist like a venus fly trap (Martin and Dunn, 2002).

Baclofen is a GABA analogue selective for GABA_B receptors used as a muscle relaxant. However, it can aggravate absence seizures, and so is not used in epilepsy. Saclofen and phaclofen are selective antagonists.

See also

• GABA_A receptor
• GABA_C receptor
• Gamma-aminobutyric acid

References

• Chen K., Lia H.Z., Yea N., Zhanga J., and Wang J.J. 2005. Role of GABAB receptors in GABA and baclofen-induced inhibition of adult rat cerebellar interpositus nucleus neurons in vitro. Brain Research Bulletin, 67(4), 310-318.
• Kandel ER, Schwartz JH, Jessell TM. Principles of Neural Science, 4th ed. pp.178-180. McGraw-Hill, New York (2000). ISBN 0838577016
• Martin I.L., and Dunn S.M.J. 2002. GABA Receptors. Tocris Cookson Ltd.
• MRC (Medical Research Counsil). 2003. Glutamate receptors: Structures and functions. University of Brisotol Centre for Synaptic Plasticity.
• Purves D., Augustine G.J., Fitzpatrick D., Katz L.C., LaMantia A.S., McNamara J.O., and Williams S.M. 2001. Neuroscience, Second Edition. Sinauer Associates, Inc.

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