Abstracts

Rationale:
Sudden unexpected death in epilepsy (SUDEP) is the fatal cause leading to the death of epilepsy patients with anti-epileptic drug resistance. However, the underlying mechanism of SUDEP remains to be poor unknown. Our previous study demonstrated that enhancement of serotonin (5-HT) synthesis by intraperitoneal (IP) injection of 5-hydroxytryptophan in brain significantly reduced seizure-induced respiratory arrest (S-IRA)  in DBA/1 mice SUDEP model. Given that 5HT2A receptor acts an important role in mediating respiration system in brain. We hypothesized that 5HT2A receptor is of great significance to modulate S-IRA and SUDEP. To test this hypothesis, we examined whether the decreased incidence S-IRA evoked by either acoustic stimulation or PTZ by blocking 5HT2A receptor by administration with ketanserin (KET), a selective antagonist of 5HT2A receptor in DBA/1 mice SUDEP model. Our results suggested that the decreased incidence of S-IRA by 5-Hydroxytryptophan (5-HTP) was significantly reversed by IP and intracerebroventricularly (ICV) injection of ketanserin in our models. Thus, our data suggested that 5-HT2AR in the brain may be a potential and specific target to prevent SUDEP.
Method:
S-IRA of DBA/1 mice evoked by acoustic stimulation using an electrical bell (96 dB SPL) without interval for 60 seconds once daily for 3-4 days starting at postnatal day 26-28 (primed DBA/1 mice) to evoke the occurrence of until the occurrence of generalized tonic-clonic seizures (GTCS). Meanwhile, S-IRA also was established by PTZ (75mg/kg, i.p.), as described previously (Zhang et al., Epilepsia,2016). Aimed at acoustic stimulation method, S-IRA was always confirmed 24 hr prior to experiment. Control group: 5-HTP or vehicle (saline) was administered i.p. once a day for 2 days and was performed 30 mins after the second administration and before acoustic stimulation. Experimental group: 5-HTP was administered i.p. once a day for 2 days and induction of S-IRA was performed 1 h after the second administration. KET was administered i.p. 30 mins before acoustic stimulation. The effects of 5-HTP and KET on S-IRA was examined and digitally recorded for offline analysis, respectively. Additionally, KET was administered by ICV injection 15 mins prior to PTZ injection as the selective antagonist of 5-HT2AR in DBA/1 mice in different groups from the same manner of 5-HTP administration.  Results  Compared with vehicle group in primed DBA/1 mice(n=6), the rate of S-IRA evoked by acoustic stimulation was significantly reduced by 5-HTP with the dosage of 200 mg/kg ,i.p once once day for two days ( p < 0.05, n=6). The lower rate of S-IRA by 5-HTP was significantly reversed by KET 20mg/kg (p < 0.01,n=6). From the another SUDEP model established by PTZ, Compared with vehicle control (n = 6), the high rate of S-IRA evoked by PTZ was significantly reduced by 5-HTP with the dosage of 200 mg/kg ,i.p daily for two days ( p < 0.05, n=7) and the lower rate of S-IRA by 5-HTP was significantly reversed by ICV injection of  KET (9.15-18.30 nmol) ( p < 0.05, n=7) . The seizure score of two models from different groups was no significantly difference ( p >