5-Hydroxytryptamine activates a barium-sensitive, cAMP-mediated potassium conductance in the leech giant glial cell

✍ Scribed by Frank C. Britz; Ingolf C. Hirth; Hans-Peter Schneider; Joachim W. Deitmer

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 210 KB
• Volume: 49
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/glia.20120

✦ Synopsis

Abstract

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~ ≈2.5 μM) 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 μM 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. © 2004 Wiley‐Liss, Inc.