Interaction of Varenicline with Classic Antiseizure Medications in the Mouse Maximal Electroshock-Induced Seizure Model.

Varenicline (VAR) is a partial agonist of brain α4ß2 nicotinic acetylcholine receptors recommended as a first line pharmacotherapy for smoking cessation. The aim of this study was to examine whether VAR affects the protective activity of four classic antiseizure medications, i.e., carbamazepine (CBZ), phenobarbital (PB), phenytoin (PHT), and valproate (VPA) on maximal electroshock (MES)-induced seizures, which may serve as an experimental model of human-generalized tonic-clonic seizures in mice. VAR administered intraperitoneally (i.p.) at a subthreshold dose of 0.5 mg/kg decreased the protective activity of CBZ against MES-induced convulsions, increasing its median effective dose (ED50) from 10.92 ± 1.0 to 18.15 ± 1.73 mg/kg (p < 0.01). The effect of VAR was dose-dependent because a lower dose of VAR (0.25 mg/kg) failed to antagonize the protective activity of CBZ. VAR administered at the subthreshold dose of 0.5 mg/kg had no impact on the protective activity of PB, PHT, and VPA in the mouse MES model. The inhibitory effect of VAR on the protective activity of CBZ against tonic-clonic convulsions most likely resulted from the pharmacodynamic mechanism(s) and was not associated with the changes in total brain concentrations of CBZ. VAR-evoked alterations in the anticonvulsive activity of CBZ may be of serious concern for epileptic tobacco smokers.

Modification of NO-cGMP Pathway Differentially Affects Diazepam- and Flunitrazepam-Induced Spatial and Recognition Memory Impairments in Rodents.

This study investigated the influence of sildenafil and methylene blue (MB), two modulators of the nitric oxide (NO)-cyclic guanosine-3',5'-monophosphate (cGMP) pathway on amnesic effects of two benzodiazepines (BZs) (diazepam (DZ) and flunitrazepam (FNZ)), in rodents-mice and rats. In the modified elevated plus maze (mEPM) and novel object recognition (NOR) tests, MB given ip at a dose of 5 mg/kg 5 min prior to DZ administration (0.25 or 1 mg/kg, sc) enhanced/induced memory impairment caused by DZ. When MB (2.5, 5, and 10 mg/kg) was applied 5 min prior to FNZ administration (0.05 and 0.1 mg/kg), an effect was opposite and memory impairment induced by FNZ was reduced. When sildenafil (2.5 and 5 mg/kg, ip) was applied 5 min prior to DZ, we observed a reduction of DZ-induced memory deficiency in the mEPM test. A similar effect of sildenafil was shown in the NOR test when the drug was applied at doses of 1.25, 2.5, and 5 mg/kg prior to DZ. In the mEPM test, sildenafil at abovementioned doses had no effects on FNZ-induced memory impairment. In turns, sildenafil administered at doses of 2.5 and 5 mg/kg increased the effect of FNZ on memory impairment in the NOR test. In conclusion, the NO-cGMP pathway is involved differentially into BZs-induced spatial and recognition memory impairments assessed using the NOR and mEPM tests. Modulators of the NO-cGMP pathway affect animal behavior in these tests in a different way depending on what benzodiazepine is applied.