Comparison between gabapentin, lamotrigine and sodium valproate on mice models of nociception, convulsion, and motor coordination

The development of newer classes of antiepileptic drugs has created several opportunities for the treatment of epilepsy as well as pain. These drugs modulate pain transmission by interacting with specific neurotransmitters and ion channels (Maizels and Mccarberg, 2005). Gabapentin may increase GABA level or block Ca channels (Petroff et al., 1996). Lamotrigine decreases the release of the excitatory neurotransmitter glutamate by blocking of sodium channels (Cheung et al., 1992). On the other hand valproate increase the brain GABA level (Davis et al., 1994) and also blocks the sodium channels (McLean and Macdonal, 1986).This study is aimed to assess and compare the effects of the new antiepileptic gabapentin the relatively new lamotrigine and the old sodium valproate on electro-shock induced convulsions, motor coordination and acute pain (induced by infra red light) in mice and chronic neuropathic pain (induced by right sciatic nerve ligation) in rats The results of the present study revealed that valproate and LTN was more effective than GBP as anticonvulsants, meanwhile the maximal effect on motor coordination was obtained with valproate followed by LTN then GBP. Moreover the three drugs did not affect the tolerability of the animals to acute thermal nociception. However they markedly attenuated the paw withdrawal latency in case of hyperalgesia induced by sciatic nerve ligation as (model of chronic neuropathic pain). At the small dose LTN was more effective than valproate and GBP had no effect while at the large dose GBP was more effective followed by LTN then valproate. Also our results revealed that, GABA-A receptors are involved in the analgesic action of GBP and valproate but not involved in that of LTN.