5-Hydroxytryptamine activates a barium-sensitive, cAMP-mediated potassium conductance in the leech giant glial cell.
5-Hydroxytryptamine (5-HT), a neurotransmitter and neuromodulator in the central nervous system of the leech Hirudo medicinalis hyperpolarizes the giant glial cell in the neuropil of segmental ganglia at micromolar concentrations. The 5-HT-evoked glial response (EC(50) approximately 2.5 microM) is mediated by a non-desensitizing, G-protein-coupled receptor and due to activation of a Ca(2+)-independent K(+) conductance. The adenylyl cyclase inhibitor SQ22,536 blocks the response to 5-HT; in the presence of 1 mM db-cAMP, but not of 1 mM db-cGMP, the glial response is suppressed. The 5-HT-evoked response is reduced by Ba(2+) with half-maximal inhibition at 50 microM Ba(2+). The results suggest that release of 5-HT from serotonergic neurons, or the maintenance of micromolar levels of extracellular 5-HT in the ganglion, may help to set the glial membrane potential close to the K(+) equilibrium potential.
Britz
Frank C
FC
Abteilung für Allgemeine Zoologie, FB Biologie, TU Kaiserslautern, Postfach 3049, D-67653 Kaiserslautern, Germany.
Hirth
Ingolf C
IC
Schneider
Hans-Peter
HP
Deitmer
Joachim W
JW
D000818:Animals; D001464:Barium / Q000494:pharmacology*; D000242:Cyclic AMP / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D047709:Hirudo medicinalis / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009457:Neuroglia / Q000187:drug effects* / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology*
D015221:Potassium Channels; D001464:Barium; D012701:Serotonin; D000242:Cyclic AMP