Seizures and seizure-induced sudden death were evoked either by acoustic stimulation or by the proconvulsant PTZ, as described previously.22 (link),30 (link) To induce AGSz in DBA/1 mice, each mouse was placed in a cylindrical acrylic glass chamber in a sound-isolated room. AGSz were induced by acoustic stimulation using an electric bell (96 dB SPL) (UC4-150, Zhejiang People’s Electronics, China). The acoustic stimulus was given for a maximum duration of 60 s or until the mouse exhibited tonic seizures, which culminated in tonic hindlimb extension and S-IRA. Mice with S-IRA were resuscitated within 5 s after the final respiratory gasp using a rodent respirator (Harvard Apparatus 680, Holliston, MA, U.S.A.).22 (link) The susceptibility to S-IRA in primed DBA/1 mice was always reconfirmed 24 h before drug or vehicle administration. In the acute treatment protocol, 5-HTP (100–150 mg/kg) or vehicle was administered intraperitoneally 1 h before induction of S-IRA. In the repeated treatment protocol, 5-HTP (50–100 mg/kg, i.p.) or vehicle was administered once a day for 2 days, and induction of S-IRA was performed 1 h after the second administration. The volume injected was 0.1–0.3 ml for each mouse. S-IRA and AGSz behaviors were videotaped for offline analysis. Recovery of S-IRA susceptibility in DBA/1 mice was tested 24 h after drug administration or at 24-h intervals thereafter until the S-IRA susceptibility returned.
Generalized clonic and/or tonic–clonic seizures were also induced in separate groups of DBA/1 and C57BL/6J mice by systemic administration of PTZ (75 mg/kg, i.p.). 5-HTP (100–200 mg/kg) or vehicle was administered once a day for 2 days, and i.p. PTZ was administered 1 h after the second treatment.
5-HTP (Cat # 107751) and PTZ (Cat # P6500) were purchased from Sigma-Aldrich (St. Louis, MO, U.S.A.) and dissolved in saline for systemic administration.