Pharmacological characterization of 5‐hydroxytryptamine‐induced depolarization of the rat isolated vagus nerve

Pharmacological characterization of 5‐hydroxytryptamine‐induced depolarization of the rat... 1 A study has been made of the pharmacology of the 5‐hydroxytryptamine (5‐HT)‐induced depolarization responses that can be recorded extracellularly from the rat isolated cervical vagus nerve. 2 Phenylbiguanide (PBG) and 2‐methyl‐5‐hydroxytryptamine (2‐methyl‐5‐HT) were found to mimic the effects of 5‐HT on the vagus nerve. Their EC50 values were respectively 2.0 fold and 3.9 fold greater than that of 5‐HT. 3 Metoclopramide behaved as a reversible competitive antagonist of depolarization induced by PBG and 2‐methyl‐5‐HT, with pKB values of 6.48 ± 0.04 and 6.64 ± 0.04, respectively. These agreed well with the pKB value of 6.60 ± 0.04 obtained previously for metoclopramide against 5‐HT on the rat vagus nerve. 5‐HT, PBG and 2‐methyl‐5‐HT had no demonstrable agonist effects at non‐5‐HT receptors on the rat vagus nerve. 4 Tropacaine and m‐chlorophenylpiperazine were found to behave as reversible competitive antagonists of 5‐HT‐induced depolarization of the vagus nerve. The pKB values were 6.29 ± 0.03 and 6.90 ± 0.03, respectively. 5 Quipazine, MDL 72222 and ICS 205–930 were also shown to be effective antagonists of 5‐HT on the vagus nerve. However, although these compounds were highly potent, they all caused a marked concentration‐dependent reduction in the amplitude of the maximum response to 5‐HT. This behaviour was not consistent with a simple reversible competitive mechanism. 6 The results are discussed with reference to the current classification of mammalian peripheral neuronal 5‐HT receptors. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png British Journal of Pharmacology Wiley

Pharmacological characterization of 5‐hydroxytryptamine‐induced depolarization of the rat isolated vagus nerve

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Publisher
Wiley
Copyright
1987 British Pharmacological Society
ISSN
0007-1188
eISSN
1476-5381
DOI
10.1111/j.1476-5381.1987.tb16844.x
Publisher site
See Article on Publisher Site

Abstract

1 A study has been made of the pharmacology of the 5‐hydroxytryptamine (5‐HT)‐induced depolarization responses that can be recorded extracellularly from the rat isolated cervical vagus nerve. 2 Phenylbiguanide (PBG) and 2‐methyl‐5‐hydroxytryptamine (2‐methyl‐5‐HT) were found to mimic the effects of 5‐HT on the vagus nerve. Their EC50 values were respectively 2.0 fold and 3.9 fold greater than that of 5‐HT. 3 Metoclopramide behaved as a reversible competitive antagonist of depolarization induced by PBG and 2‐methyl‐5‐HT, with pKB values of 6.48 ± 0.04 and 6.64 ± 0.04, respectively. These agreed well with the pKB value of 6.60 ± 0.04 obtained previously for metoclopramide against 5‐HT on the rat vagus nerve. 5‐HT, PBG and 2‐methyl‐5‐HT had no demonstrable agonist effects at non‐5‐HT receptors on the rat vagus nerve. 4 Tropacaine and m‐chlorophenylpiperazine were found to behave as reversible competitive antagonists of 5‐HT‐induced depolarization of the vagus nerve. The pKB values were 6.29 ± 0.03 and 6.90 ± 0.03, respectively. 5 Quipazine, MDL 72222 and ICS 205–930 were also shown to be effective antagonists of 5‐HT on the vagus nerve. However, although these compounds were highly potent, they all caused a marked concentration‐dependent reduction in the amplitude of the maximum response to 5‐HT. This behaviour was not consistent with a simple reversible competitive mechanism. 6 The results are discussed with reference to the current classification of mammalian peripheral neuronal 5‐HT receptors.

Journal

British Journal of PharmacologyWiley

Published: Jan 1, 1987

References

  • Influence of 5‐hydroxytryptamine uptake on the apparent 5‐hydroxytryptamine antagonist potency of metoclopramide in the rat isolated superior cervical ganglion
    IRELAND, IRELAND; STRAUGHAN, STRAUGHAN; TYERS, TYERS
  • Antagonism of 5‐hydroxytryptamine receptors by quipazine
    LANSDOWN, LANSDOWN; NASH, NASH; PRESTON, PRESTON; WALLIS, WALLIS; WILLIAMS, WILLIAMS

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