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SK channel blockade promotes burst firing in dorsal raphe serotonergic neurons
Author(s) -
Rouchet Nathalie,
Waroux Olivier,
Lamy Cédric,
Massotte Laurent,
ScuvéeMoreau Jacqueline,
Liégeois JeanFrançois,
Seutin Vincent
Publication year - 2008
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2008.06430.x
Subject(s) - bursting , dorsal raphe nucleus , serotonergic , neuroscience , chemistry , raphe nuclei , excitatory postsynaptic potential , raphe , dopaminergic , serotonin , slice preparation , potassium channel , postsynaptic potential , electrophysiology , inhibitory postsynaptic potential , biology , biophysics , dopamine , receptor , biochemistry
Previous in vivo studies have shown that blockade of small‐conductance Ca 2+ ‐activated potassium (SK) channels enhances burst firing in dopaminergic neurons. As bursting has been found to be physiologically relevant for the synaptic release of serotonin (5‐HT), we investigated the possible role of SK channels in the control of this firing pattern in 5‐HT neurons of the dorsal raphe nucleus. In these cells, bursts are usually composed of doublets consisting of action potentials separated by a small interval (< 20 ms). Both in vivo and in vitro extracellular recordings were performed, using anesthetized rats and rat brain slices, respectively. In vivo , the specific SK blocker UCL 1684 (200 μ m ) iontophoresed onto presumed 5‐HT neurons significantly increased the production of bursts in 13 out of 25 cells. Furthermore, the effect of UCL 1684 persisted in the presence of both the GABA A antagonist SR 95531 (10 m m ) and the GABA B antagonist CGP 35348 (10 m m ), whereas these agents by themselves did not significantly influence the neuronal firing pattern. In vitro , bath superfusion of the SK channel blocker apamin (300 n m ) induced bursting in only three out of 18 neurons, although it increased the coefficient of variation of the interspike intervals in all the other cells. Our results suggest that SK channel blockade promotes bursting activity in 5‐HT neurons via a direct action. An input which is present only in vivo seems to be important for the induction of this firing pattern in these cells.