title: Acute administration of a cannabinoid CB1 receptor antagonist impairs stress-induced antinociception in fish.
abstract: This study evaluated the influence of the pre-treatment with AM251 (a cannabinoid type I receptor (CB1) selective antagonist) on the stress-induced antinociception promoted by restraint in the fish Leporinus macrocephalus. The application of 3 and 5 min of restraint stress promoted an inhibition of the behavioural response to the subcutaneous injection of 3% formaldehyde (increase in locomotor activity), suggesting the activation of an antinociceptive system. The acute intraperitoneal administration of AM251 (3 mg·kg(-1)) impaired this antinociceptive response induced by 3 and 5 min of restraint stress. The fish treated with AM251 before the application of restraint stress presented an increase in locomotor activity after the subcutaneous injection of formaldehyde, similar to fish not exposed to restraint, suggesting that the stress-induced antinociception promoted by restraint in fish is probably mediated by cannabinoid CB1 receptors. The results presented in this paper suggest the participation of the endocannabinoid system in nociception modulation in fish, supporting the hypothesis that an endogenous antinociceptive system activated by restraint stress is present in fish and that the modulation of antinociception by the CB1 receptor is evolutionary well-conserved across vertebrates.
authors: School of Medicine of Ribeirão Preto, São Paulo University, Physiology Department, Bandeirantes Avenue 3900, Zip Code 14049-900, Ribeirão Preto, SP, Brazil. Electronic address: carlawolkers@yahoo.com.br.
authors: Carla Patrícia Bejo
authors: CP
authors: Wolkers
authors: School of Medicine of Ribeirão Preto, São Paulo University, Physiology Department, Bandeirantes Avenue 3900, Zip Code 14049-900, Ribeirão Preto, SP, Brazil.
authors: Augusto
authors: A
authors: Barbosa Junior
authors: School of Medicine of Ribeirão Preto, São Paulo University, Physiology Department, Bandeirantes Avenue 3900, Zip Code 14049-900, Ribeirão Preto, SP, Brazil.
authors: Leda
authors: L
authors: Menescal-de-Oliveira
authors: School of Medicine of Ribeirão Preto, São Paulo University, Physiology Department, Bandeirantes Avenue 3900, Zip Code 14049-900, Ribeirão Preto, SP, Brazil.
authors: Anette
authors: A
authors: Hoffmann
mesh_terms: D058500:Animal Fins; D000818:Animals; D063387:Cannabinoid Receptor Antagonists / Q000494:pharmacology*; D029941:Fish Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D005399:Fishes / Q000378:metabolism*; D005557:Formaldehyde; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D059226:Nociceptive Pain / Q000378:metabolism; D010147:Pain Measurement; D058748:Pain Perception / Q000187:drug effects* / Q000502:physiology; D010880:Piperidines / Q000494:pharmacology*; D011720:Pyrazoles / Q000494:pharmacology*; D043884:Receptor, Cannabinoid, CB1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012149:Restraint, Physical; D013315:Stress, Psychological / Q000188:drug therapy* / Q000378:metabolism; D013997:Time Factors
chemical_list: D063387:Cannabinoid Receptor Antagonists; D029941:Fish Proteins; D010880:Piperidines; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; D005557:Formaldehyde; C103505:AM 251
keywords: Endocannabinoid system; Formaldehyde test; Nociception; Pain; Stress; Welfare