The effect of a selective octopamine antagonist, epinastine, on pharyngeal pumping in Caenorhabditis elegans.
This paper investigates the effect of epinastine, a selective octopamine antagonist in invertebrates, in Caenorhabditis elegans. Specifically, its ability to block the inhibitory action of octopamine on C. elegans-isolated pharynx was assayed. Isolated pharynxes were stimulated to pump by the addition of 500 nM 5-hydroxytryptamine (5-HT) (113 ± 2 per 30 s, n = 15). Octopamine inhibited the 5-HT-induced pumping in a concentration-dependent manner (threshold 1-5 μM) with a 61 ± 11% inhibition with 50 μM (n = 5). Epinastine (0.1 μM) antagonized the inhibitory response to octopamine (P < 0.001; n = 15). Tyramine also inhibited pharyngeal pumping induced by 5-HT but was less potent than octopamine. Tyramine, 50 μM to 1 mM, gave a transient inhibition e.g. of 40 ± 5% at 50 μM (n = 5). A higher (10 μM) concentration of epinastine was required to block the tryamine response compared with octopamine. It is concluded that epinastine selectively antagonizes the effect of octopamine on C. elegans pharynx. Further studies are required to test its selectivity for octopamine in other tissues and other nematodes.
School of Biological Sciences, University of Southampton, Highfield Campus, Life Sciences Building 85, Southampton, SO17 1BJ, UK.
Rachel
R
Packham
Robert J
RJ
Walker
Lindy
L
Holden-Dye
D000818:Animals; D017173:Caenorhabditis elegans / Q000187:drug effects / Q000502:physiology*; D003984:Dibenzazepines / Q000494:pharmacology*; D005247:Feeding Behavior / Q000502:physiology; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology*; D009655:Octopamine / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010614:Pharynx / Q000187:drug effects* / Q000378:metabolism; D014439:Tyramine / Q000378:metabolism
D003984:Dibenzazepines; D006634:Histamine H1 Antagonists; D007093:Imidazoles; D009655:Octopamine; C053090:epinastine; D014439:Tyramine