Recent progress in development of psychotropic drugs (4) - Anticonvulsants: An overview on the mechanisms of action

Conventional anticonvulsants can be classified into three types according to their mechanisms of action: (1) those which act on voltage- dependent Na⁺ channels such as phenytoin, (2) those which act on T-type Ca²⁺ channels such as ethosuximide, and (3) those which enhance GABA receptor-mediated inhibitory neurotransmission such as phenobarbital or valproate. However, recent studies on experimental models of epilepsy have suggested that the neural mechanisms underlying experimental epileptogenesis are based on: (1) increments in cellular excitability through changes in the function of Na⁺ or Ca²⁺ channels, (2) desinhibition or inhibition failure, and (3) enhancement of excitatory amino acid receptor-mediated excitatory neurotransmission. These findings might help us to understand the recently developed anticonvulsants and vice versa. In this review, newly developed anticonvulsants are categorized according to the neural mechanisms underlying epileptogenesis, particularly actions on excitatory and inhibitory neurotransmission.