Evaluation of functional GABA_B receptors in dental pulp

γ-Aminobutyric acid (GABA) is an inhibitory neurotransmitter that is elevated in inflamed human dental pulp. Because GABA agonists are antihyperalgesic in other tissue, it is possible that GABA agonists have similar effects in dental pulp assuming that this tissue contains GABA receptors. We tested the hypothesis that dental pulp contains functional GABA_B receptors using a GTPγ³⁵S binding assay. This is a functional assay because GTPγ³⁵S will be bound to cell membranes only when activation of metabotropic receptors has lead to binding and activation of their associated Gα-proteins via release of GDP and binding of the GTPγ³⁵S. Baclofen, a GABA_B agonist, evoked GTPγ³⁵S binding in both human and bovine dental pulp. This was mediated by the GABA_B receptor because it was blocked by the selective antagonist phaclofen in both tissues. The presence of GABA and its receptor, GABA_B, suggests that this system may be relevant in the production or management of endodontic pain.