Serotonin reduces a voltage-dependent transient outward potassium current and enhances excitability of cerebellar Purkinje cells.
Utilizing current-clamp and single electrode voltage-clamp techniques we have studied the actions of serotonin (5-HT) on a transient outward voltage-dependent potassium current in adult rat Purkinje cells (PCs) in vitro. Under voltage-clamp, bath-applied 5-HT (10 nM-100 microM) reversibly depressed a transient outward potassium current in a dose-dependent manner in 24 of 26 neurons. This depression was apparent at all test command voltages. In current clamp, with normal bathing medium, 5-HT decreased the latency to first spike firing and increased the number of spikes in response to depolarization. Similar effects were evident when 4-aminopyridine was applied. In bathing medium containing TTX, Cs+ and Ni2+ to block voltage-activated currents, 5-HT increased the trajectory of the electrotonic membrane response elicited by depolarizing current injection. Enhanced responsiveness of PCs by 5-HT was not related to changes in membrane potential or input resistance. These experiments indicate that one mechanism by which 5-HT can increase the excitability of PCs is via reduction of a transient outward current.
Wang
Y
Y
Department of Neurology, Texas Tech University Health Sciences Center, Lubbock 79430.
Strahlendorf
J C
JC
Strahlendorf
H K
HK
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D002531:Cerebellum / Q000502:physiology; D002586:Cesium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009532:Nickel / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011689:Purkinje Cells / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D002586:Cesium; D012701:Serotonin; D013779:Tetrodotoxin; D019789:Tetraethylammonium; D009532:Nickel; D015761:4-Aminopyridine