Excitation of substantia nigra pars compacta neurones by 5-hydroxy-tryptamine in-vitro.
Incoming serotonergic fibres are known to make direct synaptic contact with dopamine-containing neurones in the substantia nigra pars compacta (SNc). However, the effects of 5-HT (5-hydroxytryptamine) on these cells have not been thoroughly investigated. In the present study we show that application of 10-50 microM 5-HT increases the firing frequency of SNc neurones in-vitro, and produces inward rectification in a voltage region negative to -50mV. This effect is sensitive to extracellular Cs+, but not to Ba2+, and has similar properties as the intrinsic inward rectifier current, Ih. Antagonists of the 5-HT1A and 5-HT2 receptors were inefficacious. It is concluded that 5-HT excites SNc neurones via an enhancement of the conductance underlying Ih.
Nedergaard
S
S
Institute of Physiology, Aarhus University, Denmark.
Flatman
J A
JA
Engberg
I
I
D000818:Animals; D001464:Barium / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D004566:Electrodes; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*; D013378:Substantia Nigra / Q000166:cytology / Q000187:drug effects*
D007473:Ion Channels; D002586:Cesium; D001464:Barium; D012701:Serotonin; D004298:Dopamine