Cannabinoid inhibition of the capsaicin-induced calcium response in rat dorsal root ganglion neurones.

Cannabinoids have marked inhibitory effects on somatosensory processing, which may arise from actions at both peripheral and central cannabinoid receptors. Here, the effect of a synthetic cannabinoid agonist HU210 on capsaicin-evoked responses in adult rat dorsal root ganglion (DRG) neurones was studied. The vanilloid capsaicin produced a concentration-related increase in intracellular calcium in DRG neurones, which was significantly inhibited by HU210 (1 microM). The cannabinoid CB(1) receptor antagonist SR141716A (1 microM) had no effect alone and did not influence the response to capsaicin but significantly reversed the inhibitory effect of HU210. These data indicate that DRG CB(1) receptors are functional and can inhibit nociceptive responses.