Evaluation of potential anticonvulsant fluorinated N-benzamide enaminones as T-type Ca2+ channel blockers

Trifluoromethylated N-benzamide enaminones have been identified as potential anticonvulsants for the treatment of drug-resistant epilepsy. T-type CA²⁺ channels are an important target for anti-seizure medications. Our laboratory has developed several fluorinated N-benzamide enaminone analogs that were evaluated by their ability to target T-type CA²⁺ channels. Using whole cell voltage-clamp recordings, we identified two meta-trifluoromethyl N-benzamide enaminones with a significant inhibitory effect on T-type CA²⁺ channels. These compounds had no effect on voltage-activated Na⁺ channels. We also evaluated the effect of the fluorinated N-benzamide enaminone analogs on the T-type CA²⁺ channel subunits Cav3.2 and Cav3.3. The meta-trifluoromethyl N-benzamide enaminone lead analogs altered the steady-state inactivation of Cav3.2 T-type CA²⁺ channels, which resulted in a significant increase in the inactivation recovery time of the channels. There was no effect of fluorinated N-benzamide enaminone analogs on the gating mechanism of T-type CA²⁺ channels, as proven by the lack of effect on the activation and inactivation time constant of CA²⁺ currents. On the contrary, the meta-trifluoromethyl N-benzamide enaminone lead analogs altered the gating mechanism of Cav3.3 T-type CA²⁺ channels, as proven by the reduction in the activation and inactivation time constant of the channels. There was no effect on the inactivation kinetics of Cav3.3 T-type CA²⁺ channels. The present results demonstrate that meta-substituted trifluoromethyl N-benzamide enaminone analogs target T-type CA²⁺ channels by different mechanisms depending on the channel subunit. Meta-trifluoromethyl N-benzamide enaminone analogs can potentially lead to the design of more specific blockers of T-type CA²⁺ channels for the treatment of epileptic seizures.