Pharmacological properties of l-glutamate receptors associated with the crayfish hindgut.
Pharmacological agents were used to characterize glutamate receptors associated with crayfish hindgut. l-Glutamate reliably increased tonus in isolated hindguts of Procambarus clarkii and suppressed spontaneous hindgut contractions at concentrations of 10 micromol l(-1) or higher. Quisqualate and ibotenate mimicked the effects of L-glutamate. Experiments with strips and rings of hindgut tissue indicate that glutamate acts on both circular and longitudinal muscles. Hindgut contractions were not affected by (+/-)-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionoic acid, N-methyl- d-aspartate, domoate or the metabotropic glutamate receptor agonist, (1S,3R)-1-amino-1-carboxycyclopentane-3-acetic acid. Picrotoxin, at 50 micromol l(-1), did not alter the ibotenate-induced reduction in contraction frequency, suggesting that this effect is not produced by inhibitory glutamate receptors. The glutamate-induced increase in tonus was antagonized by Joro spider toxin, JSTX-3. Thus, glutamate receptors associated with crayfish hindgut muscles are of the quisqualate type but are also sensitive to ibotenate. Elevating extracellular potassium concentration mimicked all of the effects of glutamate, suggesting that excessive depolarization may contribute to the suppression of contractions at high agonist concentrations.
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Department of Biological Sciences, Brock University, 500 Glenridge Avenue, St. Catharines, ON, L2S 3A1, Canada.
Sammahin
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Richardson
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Mercier
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D000818:Animals; D001181:Arthropods; D003400:Astacoidea; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004594:Electrophysiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018698:Glutamic Acid / Q000494:pharmacology*; D006571:Heterocyclic Compounds / Q000494:pharmacology; D007051:Ibotenic Acid / Q000494:pharmacology; D007422:Intestines / Q000187:drug effects* / Q000502:physiology; D007608:Kainic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009498:Neurotoxins / Q000494:pharmacology; D011073:Polyamines / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D016318:Quisqualic Acid / Q000494:pharmacology; D017470:Receptors, Glutamate / Q000187:drug effects / Q000502:physiology*
D018690:Excitatory Amino Acid Agonists; D006571:Heterocyclic Compounds; C426070:JSTX-3; D009498:Neurotoxins; D011073:Polyamines; D017470:Receptors, Glutamate; D007051:Ibotenic Acid; D018698:Glutamic Acid; D016318:Quisqualic Acid; C012301:domoic acid; D011188:Potassium; D007608:Kainic Acid