Hemopressin increases penicillin-induced epileptiform activity in rats

Abstract

OBJECTIVE: Hemopressin (Hp) is the first peptide ligand described for the CB1 cannabinoid receptor. Therefore, we aimed to investigate the effect of hemopressin on pencillin-induced epileptiform activity by using electrophysiological recording (ECoG) technique. METHODS: Male Wistar rats were anesthetized with urethane (1.25 g/kg), and epileptiform activity was induced by intracortical injection of penicillin (500 IU). Animals were randomly divided into eight groups. Subsequently, the rats were administered with saline or hemopressin as follows: saline control group (Group I: 2 μl/i.c. v/saline), hemopressin groups (Group II: 0.025 μg/i.c. v; Group III: 0.075 μg/i.c. v; Group IV: 0.15 μg/i.c. v; Group V: 0.3 μg/i.c. v; Group VI: 0.6 μg/i.c. v; Group VII: 1.2 μg/i.c. v; Group VIII: 2.4 μg/i.c. v). The various doses of hemopressin were injected intracerebroventricularly (i.c. v) 30 minutes after penicillin (2.5μl) injection. After hemopressin injection, ECoGs were recorded for three hours. RESULTS: Hp at doses of 0.075, 0.15, 0.3, 0.6, 1.2 and 2.4 μg/kg significantly increased the frequency of epileptiform ECoG activity compared to penicillin-injected group without changing the amplitude. The 0.6 μg hemopressin was the most effective dose to increase the epileptiform activity (p < 0.05) while the dose of 0.025 μg hemopressin was non-effective (p > 0.05). CONCLUSIONS: The results of this study provided electrophysiological evidence for hemopressin to be modulating penicillin-induced epileptiform activity by acting as CB1 receptor antagonist. Further studies are required to elucidate the involved mechanism underlying this effect (Fig. 3, Ref. 40). Text in PDF www.elis.sk.