Whole-cell recordings of inwardly rectifying K+ currents activated by 5-HT1A receptors on dorsal raphe neurones of the adult rat
1. An inwardly rectifying K+ current activated by serotonin (5-HT) was recorded from acutely isolated adult dorsal raphe (DR) neurones using the whole-cell recording mode of the patch clamp technique. 2. The 5-HT-induced K+ current (I5-HT) was only visible at an [K+]0 > 5 mM and it was observed i...
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Veröffentlicht in: | The Journal of physiology 1993-09, Vol.469 (1), p.387-405 |
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Zusammenfassung: | 1. An inwardly rectifying K+ current activated by serotonin (5-HT) was recorded from acutely isolated adult dorsal raphe (DR)
neurones using the whole-cell recording mode of the patch clamp technique. 2. The 5-HT-induced K+ current (I5-HT) was only
visible at an [K+]0 > 5 mM and it was observed in 69% of the cells. 3. The reversal potential for I5-HT was close to the potassium
equilibrium potential and was shifted by 51 mV per 10-fold change in [K+]0 indicating that I5-HT was carried predominantly
by K+. The chord conductance of I5-HT at -90 mV was proportional to the external [K+] raised to a fractional power. 4. A dose-response
relationship revealed that I5-HT was activated with an ED50 of 30 nM. Ba2+ (0.1 mM) blocked I5-HT completely. Spiperone reversibly
antagonized the response to 5-HT and 8-OHDPAT (8-hydroxy-2-(di-n-propylamino)tetralin) mimicked the response indicating that
the receptor activated was of the 5-HT1A subtype. 5. The response to 5-HT was largely prevented by in vitro pretreatment of
the cells with pertussis toxin (PTX) indicating the involvement of a PTX-sensitive G-protein in the transduction mechanism.
6. cAMP and lipoxygenase metabolites, both implicated in the modulation of similar currents in other preparations, were found
not to alter the effectiveness of 5-HT. 7. Glibenclamide and tolbutamide, blockers of the ATP-regulated K+ channel, did not
reduce the effect of 5-HT in DR neurones. 8. These results show that in acutely isolated adult DR neurones 5-HT activates
an inwardly rectifying K+ current and this involves a PTX-sensitive G-protein in the transduction pathway which may interact
with the K+ channel directly. |
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ISSN: | 0022-3751 1469-7793 |
DOI: | 10.1113/jphysiol.1993.sp019819 |