Volume 97, Issue 1 p. 27-40
Free Access

The properties of 5-HT3 receptors in clonal cell lines studied by patch-clamp techniques

Jeremy J. Lambert

Corresponding Author

Jeremy J. Lambert

Neuroscience Research Group, Department of Pharmacology & Clinical Pharmacology, Ninewells Hospital and Medical School, Dundee University, Dundee DD1 9SY

Neuroscience Research Group, Department of Pharmacology & Clinical Pharmacology, Ninewells Hospital and Medical School, Dundee University, Dundee DD1 9SYSearch for more papers by this author
John A. Peters

John A. Peters

Neuroscience Research Group, Department of Pharmacology & Clinical Pharmacology, Ninewells Hospital and Medical School, Dundee University, Dundee DD1 9SY

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Tim G. Hales

Tim G. Hales

Neuroscience Research Group, Department of Pharmacology & Clinical Pharmacology, Ninewells Hospital and Medical School, Dundee University, Dundee DD1 9SY

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John Dempster

John Dempster

Department of Physiology and Pharmacology, Royal College, Strathclyde University, George St., Glasgow G1 1XW

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First published: May 1989
Citations: 104

Abstract

  • 1

    The characteristics of transmembrane currents evoked by 5-hydroxytryptamine (5-HT) in the neuroblastoma x Chinese hamster brain cell line NCB-20 and neuroblastoma clonal cell line N1E-115 have been studied under voltage-clamp conditions by the whole-cell recording and outside-out membrane patch modes of the patch-clamp technique.

  • 2

    In 73% of NCB-20 cells examined (n = 221), and all N1E-115 cells studied (n = 80), 5-HT (10 μm) elicited a transient inward current at negative holding potentials, this being associated with an increase in membrane conductance. In both cell lines responses to 5-HT reversed in sign at a potential of approximately −2mV and demonstrated inward rectification.

  • 3

    The reversal potential of 5-HT-induced currents (E5-HT) recorded from either NCB-20 or N1E-115 cells was unaffected by total replacement of internal K+ by Cs+. In N1E-115 cells, reducing internal K+ concentration from 140 to 20 mm produced a positive shift in E5-HT of approximately 28 mV, whereas reducing external Na+ from 143 to 20 mm was associated with a negative shift in E5-HT of about 37 mV. A large reduction in internal Cl concentration (from 144 to 6 mm) had little effect on E5-HT.

  • 4

    5-HT-induced currents of NCB-20 cells were unaffected by methysergide (1 μm) or ketanserin (1 μm), but were reversibly antagonized by GR38032F (0.1–1.0 nm) with an IC50 of 0.25 nm. GR 38032F (0.3 nm) reduced 5-HT-induced currents in N1E-115 cells to approximately 26% of their control value.

  • 5

    On outside-out membrane patches excised from both NCB-20 and N1E-115 cells, 5-HT induced small inward currents which could not be clearly resolved into discrete single channel events. Such responses were: (i) reversibly antagonized by GR 38032F (1 nm) (ii) reversed in sign at 0 mV, and (iii) subject to desensitization.

  • 6

    Fluctuation analysis of inward currents evoked by 5-HT (1 μm) in N1E-115 cells suggests that 5-HT gates a channel with a conductance of approximately 310fS. Such a relatively small conductance could readily explain why the response of outside-out membrane patches to 5-HT cannot at present be resolved into clear single channel events.