Altered expression and function of small-conductance (SK) Ca(2+)-activated K+ channels in pilocarpine-treated epileptic rats.
Small conductance calcium (Ca(2+)) activated SK channels are critical regulators of neuronal excitability in hippocampus. Accordingly, these channels are thought to play a key role in controlling neuronal activity in acute models of epilepsy. In this study, we investigate the expression and function of SK channels in the pilocarpine model of mesial temporal lobe epilepsy. For this purpose, protein expression was assessed using western blotting assays and gene expression was analyzed using TaqMan-based probes and the quantitative real-time polymerase chain reaction (qPCR) comparative method delta-delta cycle threshold ( big up tri, open big up tri, openCT) in samples extracted from control and epileptic rats. In addition, the effect of SK channel antagonist UCL1684 and agonist NS309 on CA1 evoked population spikes was studied in hippocampal slices. Western blotting analysis showed a significant reduction in the expression of SK1 and SK2 channels at 10days following status epilepticus (SE), but levels recovered at 1month and at more than 2months after SE. In contrast, a significant down-regulation of SK3 channels was detected after 10days of SE. Analysis of gene expression by qPCR revealed a significant reduction of transcripts for SK2 (Kcnn1) and SK3 (Kcnn3) channels as early as 10days following pilocarpine-induced SE and during the chronic phase of the pilocarpine model. Moreover, bath application of UCL1684 (100nM for 15min) induced a significant increase of the population spike amplitude and number of spikes in the hippocampal CA1 area of slices obtained control and chronic epileptic rats. This effect was obliterated by co-administration of UCL1684 with SK channel agonist NS309 (1microM). Application of NS309 failed to modify population spikes in the CA1 area of slices taken from control and epileptic rats. These data indicate an abnormal expression of SK channels and a possible dysfunction of these channels in experimental MTLE.
Oliveira
Mauro S
MS
Departamento de Fisiologia e Farmacologia, Centro de Ciências da Saúde, Universidade Federal de Santa Maria, RS, Brazil.
Skinner
Frank
F
Arshadmansab
Massoud F
MF
Garcia
Ileana
I
Mello
Carlos F
CF
Knaus
Hans-Günther
HG
Ermolinsky
Boris S
BS
Otalora
Luis F Pacheco
LF
Garrido-Sanabria
Emilio R
ER
D000367:Age Factors; D000473:Alkanes / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D004347:Drug Interactions; D005786:Gene Expression Regulation / Q000187:drug effects*; D006624:Hippocampus / Q000473:pathology; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology; D018721:Muscarinic Agonists / Q000009:adverse effects*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D010091:Oximes / Q000494:pharmacology; D010862:Pilocarpine / Q000009:adverse effects*; D011806:Quinolinium Compounds / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D013226:Status Epilepticus / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology; D013997:Time Factors
C110349:6,10-diaza-3(1,3),8(1,4)dibenzena-1,5(1,4)diquinolinacyclodecaphane; C493327:6,7-dichloro-1H-indole-2,3-dione 3-oxime; D000473:Alkanes; D007211:Indoles; D018721:Muscarinic Agonists; D010091:Oximes; D011806:Quinolinium Compounds; D051640:Small-Conductance Calcium-Activated Potassium Channels; D010862:Pilocarpine