Combined effects of gabapentin with verapamil and metoprolol on cardiovascular function of anesthetized male rats

Gabapentin (GBP), at high plasma concentrations, negatively impacts cardiovascular function, causing bradycardia, hypotension, and impaired left ventricular (LV) function in rats. This study examines the combined effects of GBP with Verapamil (Ver) or Metoprolol (Met) on cardiovascular function in anesthetized male rats and its impact on Ca²⁺ current and calmodulin (CaM) protein expression in cultured H9c2 cells. Twenty-two male Sprague Dawley rats were assigned to four groups: Saline + Ver, GBP + Ver, Saline + Met, and GBP + Met. Under isoflurane anesthesia, rats underwent ECG monitoring and LV hemodynamic and blood pressure (BP) assessment. GBP (50 mg/kg) was administered intravenously, followed by Ver (0.05-0.4 mg/kg) or Met (0.5 mg/kg). In the first experiment, Ver induced a dose-dependent reduction in BP, heart rate (HR), and maximal dP/dt, while increasing minimal dP/dt, in both saline control and GBP-treated groups with the latter group showing greater effects. In the second experiment, GBP significantly reduced BP, HR, and maximal dP/dt while increasing minimal dP/dt compared to baseline. These effects were further exacerbated by Met, leading to greater reductions in BP, HR, and maximal dP/dt, and increases in minimal dP/dt compared to Met alone. In addition, in vitro experiments demonstrated that GBP reduced Ca²⁺ current and downregulated CaM protein. These findings suggest that, at high plasma concentrations, GBP enhances the negative chronotropic, negative inotropic, and hypotensive effects of both Ver and Met, further highlighting the need for additional preclinical and clinical studies to characterize the potential drug interactions between GBP and calcium channel blockers or beta-1 blockers, particularly in patients with cardiovascular disease.