The 5-HT7 receptor antagonist SB-269970 alleviates seizure activity and downregulates hippocampal c-Fos expression in pentylenetetrazole-induced kindled rats

Abstract

Objectives: Recently, studies have demonstrated that serotonin type 7 receptors (5-HT7) have conflincting effects on neuronal excitability in different brain regions. However, the effect of 5-HT7 on seizures has not been exactly elucidated yet. Therefore, our aim in this study was to investigate the effects of 5-HT7 antagonist SB-269970 on pentylenetetrazole (PTZ) induced fully kindled rats.

Methods: In the study, 32 adult male Wistar Albino rats (weighing 220-260 g) were used. Rats were injected with PTZ (35 mg/kg) intraperitoneally every other day to generate kindling model. 5-CT (0.1 mg/kg) and SB-269970 (1 mg/kg) were administered 30 min before acute seizure induction with PTZ (35 mg/kg). Seizure stages were determined according to the Racine scale. After electrocorticography (ECoG) recordings of seizure-induced rats were obtained, the animals were sacrificed by decapitation. The hippocampal GABA levels were determined by ELISA kit and the number of c-Fos positive neurons in the hippocampal dentate gyrus (DG), CA1 and CA3 areas were measured by immunohistochemical method.

Results: The results showed that SB-269970 reduced the number of spikes, percent seizure duration and duration of generalized tonic-clonic seizures (dGTCS), while increasing the onset time of generalized tonic-clonic seizures (oGTCS). The hippocampal GABA levels were significantly increased in the SB-269970 group compared with the PTZ group. In addition, SB-269970 reduced the number of c-Fos positive cells in hippocampal CA1 area.

Discussion: 5-HT7 antagonist SB-269970 displays anticonvulsant effects on PTZ-induced seizures in fully kindled rats and these effects may be related to GABAergic activity in the hippocampus.

Keywords: 5-HT receptor; 5-HT7; GABA; SB-269970; c-Fos; seizure.