Effects of gap junctions blockers on fast ripples and connexin in rat hippocampi after status epilepticus.

OBJECTIVE: To assess the dynamic changes in the average and peak spectral power of fast ripples (FRs) in the hippocampi after interventions with valproate sodium (VPA), carbenoxolone (CBX) and quinine (QUIN).

METHOD: Adult rats were used to establish a lithium-pilocarpine (pilo) epileptic model, and were assigned to a lithium-pilocarpine (PILO), VPA + PILO, QUIN + PILO or CBX + PILO group. Intracranial electroencephalography was performed before and after status epilepticus (SE). The hippocampal connexin (CX) 43, CX32 and CX36 expressions were analyzed via western blotting.

RESULTS: The time required for the disappearance of SE after chloral hydrate injection was lower in the intervention groups than in the PILO group (p < 0.05). Seizures induced CX43 expression, but had no significant effects on CX36 or CX32 expressions. Pretreatment with VPA, QUIN and CBX inhibited CX43, CX36 and CX32 expression after SE. The average spectral power of the FRs was significantly lower in the VPA + PILO and QUIN + PILO groups than in the PILO group at 10 min after SE, 10 min before chloral hydrate injection, and 10 min after chloral hydrate injection (p < 0.05). The average spectral power of FRs was lower in the CBX + PILO group than in the PILO group at 10 min after SE (p < 0.05). The average spectral power of FRs in the 3 intervention groups recovered to the baseline level at 10 min after chloral hydrate injection and persisted for 3 days after SE. The dynamic changes in the average and peak spectral power of FRs were similar.

SIGNIFICANCE: After SE, CX may participate in pathological FR generation by establishing abnormal electrical synaptic transmission. Gap junction blockers can inhibit various CX expressions, and thus decrease FR energy and alleviate the degree of seizure. These findings could contribute to the development of new anti-epileptic drugs with novel mechanistic targets.