Inhibition of fatty acid amide hydrolase (FAAH) reduces spinal nociceptive responses and expression of spinal long-term potentiation (LTP)

Fatty acid amide hydrolase (FAAH) is an enzyme that metabolizes endocannabinoids and fatty acid amides possibly linked to activation of the opioid system. To examine how this enzyme affects spinal signalling, electrophysiological recordings in the dorsal horn and qPCR on dorsal horn tissue following systemic administration of the FAAH inhibitor URB597 (0.3 and 1.0 mg/kg i.v.) and spinal administration of the opioid receptor antagonist naloxone (0.1 μg/μl i.th.), were performed. The present data showed that the suppressive effect of the FAAH inhibitor URB597 (1.0 mg/kg i.v.) on the spinal nociceptive responses was prevented by spinal administration of the opioid receptor antagonist naloxone (0.1 μg/μl i.th.). Moreover, the present findings demonstrated that the FAAH inhibitor URB597 (1.0 mg/kg i.v.) partly reversed expression of spinal long-term potentiation (LTP) and also attenuated the LTP-associated increased Zif expression. We conclude that pharmacological inactivation of FAAH may be a promising strategy to inhibit the development of central hyperalgesia; thereby reinforcing the role of FAAH as a potential therapeutic target.