Anti-nociceptive effects of taurine and caffeine in sciatic nerve ligated wistar rats: involvement of autonomic receptors

Abstract

In this study, we investigated the effects of co-administration of taurine and caffeine on thermally induced pain in sciatic nerve ligated rats as well as the roles of autonomic receptors. Rats were rendered neuropathic by unilateral sciatic nerve ligation. The anti-hyperalgesic effect of combined systemic (i.p.) administration of taurine and caffeine were assessed using tail flick tests and hot plate test for two weeks. To determine the involvement of autonomic nervous system, the study examined how administration of cholinergic (atropine and hexamethonium) and adrenergic (prazosin and propranolol) receptor blockers altered the combined effect of taurine and caffeine. Likewise, the serum level of oxidative stress marker malondialdehyde (MDA) was evaluated. The results showed that co-administration of taurine and caffeine attenuated thermal hyperalgesia in sciatic nerve ligated rats as shown by significant (p<0.05) increase in tail and paw withdrawal latencies in the treated groups compared to the ligated control group after two weeks of administration. The anti nociceptive effects were reversed by pre-treatment with cholinergic blockers especially atropine while the adrenergic blockers spared the effects of taurine and caffeine. Also, the increase in tissue level of MDA induced by sciatic nerve ligation was significantly attenuated by combined administration of high dose of taurine and caffeine. It can be concluded that co-administration of taurine and caffeine attenuates thermal hyperalgesia in sciatic nerve-ligated rats (a model of neuropathic pain) and this effect involves cholinergic system. The findings suggest that coadministration of taurine and caffeine might be useful for the treatment of neuropathic pain.

Keywords: Caffeine, taurine hyperalgesia, neuropathic pain,