Interaction of Delta sleep-inducing peptide and valproate on metaphit audiogenic seizure model in rats

Abstract

Effects of valproate (VPA), a conventional antiepileptic drug and natural delta sleep-inducing peptide (DSIP) on metaphit (1-[1-(3-isothiocyanatophenyl)-cyclohexyl]-piperidine)-induced audiogenic reflex epilepsy were studied. For the purpose of the study, valproate in the doses of 50 or 75 mg/kg and DSIP (1.0 mg/kg) was i.p. injected either alone or in combination to adult Wistar male rats with fully developed metaphit seizures after eight audiogenic testing. The animals were stimulated using an electric bell (100 +/- 3 dB and 5-8 kHz, for 60 s) 60 min after metaphit injection and afterwards at hourly intervals during the experiment. For EEG recording and power spectra analysis, three gold-plated screws were implanted into the scull. In EEGs of metaphit-treated animals polyspikes, spike-wave complexes and sleep-like patterns were recorded, while the power spectra were increased. Combined treatment of metaphit-induced seizures with valproate and DSIP was more effective than drugs alone especially during 4 h after administration. None of the applied dose combinations eliminated the EEG signs of metaphit-provoked epileptiform activity. Taken together, the results of the present study suggest that the combinations of valproate and DSIP should be considered as beneficial polytherapy in metaphit model of epilepsy.

Fig. 1

EEG records (left tracings) from the left frontal—right parietal cortical leads. Right-sequential power spectra of the corresponding EEG activity on the left (μV²): (a) control rats (baseline state without signs of epileptiform activity), (b) isolated spiking activity observed during few hours upon metaphit administration, (c) EEG record of maximal motor seizure response (grade 3) during sound stimulation (100 ± 3 dB, 60 s) in a metaphit-treated rat, irregular low-frequency synchronized spikes (6–8 Hz), and the corresponding intensive power spectra exceeding about three times of the baseline, (d) EEG changes on AGS in metaphit-treated rats 1 h after injection of the VPA (75 mg/kg ) and DSIP (1.0 mg/kg, i.p.) drug combination. Note isolated spiking activity and mildly reduced power spectra Time calibration 1 s; amplitude calibration 50 μV

Fig. 2

The reduction of incidence of metaphit seizures expressed in percentage after 8 h followed by different valproate doses (50 and 75 mg/kg) either alone or with DSIP (1 mg/kg) in drug combination. All animals were exposed to an intense AGS (100 ± 3 dB, 60 s) at hourly intervals after the injection. Y-axis—reduction of seizure incidence s; X-axis—time (h) after metaphit administration. For the comparison of the number of rats with convulsing activity between groups, we used Fisher`s exact probability test (*P < 0.05, **P < 0.01): mp—metaphit (10 mg/kg); VPA50−mp + valproate 50 mg/kg; VPA75−mp + valproate 75 mg/kg; DSIP−mp + DSIP, and two combination groups VPA50 + DSIP−mp + valproate 50 mg/kg + DSIP and VPA75 + DSIP−mp + valproate 75 mg/kg, +DSIP. Comparison of the number of rats convulsing between (a–j): a—mp vs. VPA75; b—mp vs. VPA75 + DSIP; c—VPA50 vs. VPA75; d—VPA50 vs. DSIP; e—VPA50 vs. VPA50 + DSIP; f—VPA50 vs. VPA75 + DSIP; g—VPA75 vs. DSIP; h—DSIP vs. VPA50 + DSIP; i—DSIP vs. VPA75 + DSIP; and j—VPA50 + DSIP vs. VPA75 + DSIP

Fig. 3

Time course of mean seizure grade reduction upon metaphit (10 mg/kg i.p.) injection followed by VPA, DSIP, and their combination after 8 h. All animals were exposed to an intense AGS (100 ± 3 dB, 60 s) at hourly intervals after the injection. Severity of seizures (expressed as a seizure score) was determined by a descriptive rating scale ranging from 0 to 3 (0—no response; 1—wild running only; 2—clonic seizures; and 3—tonic extension). Comparison of mean seizure grades between experimental groups was evaluated by Kruskal Wallis ANOVA test (*P < 0.05, **P < 0.01). X axis—time after metaphit administration (h) Y axis—reduction of seizure intensity in percentages; For more details see Fig. 2