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The properties of 5‐HT 3 receptors in clonal cell lines studied by patch‐clamp techniques
Author(s) -
Lambert Jeremy J.,
Peters John A.,
Hales Tim G.,
Dempster John
Publication year - 1989
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1989.tb11920.x
Subject(s) - methysergide , patch clamp , ketanserin , membrane potential , biophysics , 5 ht receptor , voltage clamp , chemistry , receptor , electrophysiology , endocrinology , medicine , serotonin , biology , biochemistry
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 μ m ) 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 (E 5‐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 m m produced a positive shift in E 5‐HT of approximately 28 mV, whereas reducing external Na + from 143 to 20 m m was associated with a negative shift in E 5‐HT of about 37 mV. A large reduction in internal Cl − concentration (from 144 to 6 m m ) had little effect on E 5‐HT . 4 5‐HT‐induced currents of NCB‐20 cells were unaffected by methysergide (1 μ m ) or ketanserin (1 μ m ), but were reversibly antagonized by GR38032F (0.1–1.0 n m ) with an IC 50 of 0.25 n m . GR 38032F (0.3 n m ) 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 n m ) (ii) reversed in sign at 0 mV, and (iii) subject to desensitization. 6 Fluctuation analysis of inward currents evoked by 5‐HT (1 μ m ) 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.