Serotonin activates a Ca(2+)-dependent K(+) current in identified peptidergic neurons from the crayfish.
The effects of 5-hydroxytryptamine (5-HT) were investigated in red pigment concentrating hormone (RPCH)-containing neurons isolated from the X-organ of the crayfish (Procambarus clarkii). Under current-clamp conditions and using the gramicidin-perforated-patch configuration, 5-HT elicited a prolonged hyperpolarization that suppressed neuronal firing concomitant with an increase in membrane conductance. Under voltage-clamp conditions, 5-HT evoked an outward current at a holding potential of -50 mV. This current reversed at an E(K) of -90 mV, which shifted by 30 mV when the extracellular K(+) concentration was increased from 5.4 to 19 mmol l(-1). The effect of 5-HT was dose-dependent within the range 1-100 micromol l(-1) and followed simple Michaelis-Menten kinetics, with a half-maximal response being elicited at 10 micromol l(-1). Preincubation with charybdotoxin (100 nmol l(-1)), tetraethylammonium (500 micromol l(-1)) or methysergide (100 micromol l(-1)) was effective in blocking the response to 5-HT. These results suggest that 5-HT is an inhibitory mediator of the release of red pigment concentrating hormone by acting on a Ca(2+)-dependent K(+) current.
Alvarado-Alvarez
R
R
Departamento de Fisiología, Biofísica y Neurociencias, CINVESTAV and División de Estudios de Postgrado e Investigación, Facultad de Medicina UNAM, México.
Aréchiga
H
H
García
U
U
D000818:Animals; D003400:Astacoidea / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology*; D004553:Electric Conductivity; D005260:Female; D007700:Kinetics; D008297:Male; D009474:Neurons / Q000737:chemistry / Q000502:physiology*; D009842:Oligopeptides / Q000032:analysis; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D012701:Serotonin / Q000494:pharmacology*
D009842:Oligopeptides; D015221:Potassium Channels; D012701:Serotonin; C022059:red pigment-concentrating hormone; D011188:Potassium; D002118:Calcium; D011761:Pyrrolidonecarboxylic Acid