Specific regulation of mechanical nociception by G β5 involves GABA-B receptors

Abstract

Mechanical, thermal, and chemical pain sensation is conveyed by primary nociceptors, a subset of sensory afferent neurons. The intracellular regulation of the primary nociceptive signal is an area of active study. We report here the discovery of a Gβ5-dependent regulatory pathway within mechanical nociceptors that restrains antinociceptive input from metabotropic GABA-B receptors. In mice with conditional knockout (cKO) of the gene that encodes Gβ5 ( Gnb5) targeted to peripheral sensory neurons, we demonstrate the impairment of mechanical, thermal, and chemical nociception. We further report the specific loss of mechanical nociception in Rgs7-Cre ^+/– Gnb5 ^fl/fl mice but not in Rgs9-Cre ^+/– Gnb5 ^fl/fl mice, suggesting that Gβ5 might specifically regulate mechanical pain in regulator of G protein signaling 7–positive (Rgs7 ⁺) cells. Additionally, Gβ5-dependent and Rgs7-associated mechanical nociception is dependent upon GABA-B receptor signaling since both were abolished by treatment with a GABA-B receptor antagonist and since cKO of Gβ5 from sensory cells or from Rgs7 ⁺ cells potentiated the analgesic effects of GABA-B agonists. Following activation by the G protein–coupled receptor Mrgprd agonist β-alanine, enhanced sensitivity to inhibition by baclofen was observed in primary cultures of Rgs7 ⁺ sensory neurons harvested from Rgs7-Cre ^+/– Gnb5 ^fl/fl mice. Taken together, these results suggest that the targeted inhibition of Gβ5 function in Rgs7 ⁺ sensory neurons might provide specific relief for mechanical allodynia, including that contributing to chronic neuropathic pain, without reliance on exogenous opioids.

Abstract