Studies on the Action of Biogenic Amines on Cockroach Heart

Abstract

Measurement of the beat of the semi-isolated cockroach heart, by impedance conversion, showed that the whole abdominal heart of large nymphs or adults responded to low concentrations of acetylcholine (ACh) or 5-hydroxytryptamine (5-HT) by increasing the rate of heartbeat. Preparations, which included 2-chamber sections of the abdominal heart, showed vastly reduced responses to ACh compared to the responses of the whole abdominal heart. Responses to 5-HT were similar in both preparations. Following assay with 5-HT, the cockroach heartbeat often developed marked regularity. ACh assays produced such regularity only rarely. The sectioned cockroach heart preparation was decreasingly responsive to 5-HT > synephrine > octopamine > tryptamine > dopamine > tyramine. Dose-response curves revealed that the antagonist 501 c interacted competitively with 5-HT on the cockroach heart preparation. 501 c appeared to be a non-competitive antagonist to octopamine, suggesting that 5-HT and octopamine act at separate receptor sites on the myocardium. Experiments in which solutions of dibutyryl cyclic AMP, dibutyryl cyclic GMP, or aminophylline were continuously perfused on the cockroach heart, failed to establish that cyclic nucleotides mediate neurotransmitter or hormone action on this tissue. Cockroach hearts were not responsive to prostaglandin E1, F1, picrotoxin, L-glutamate, or ATP below 10−3-10−4M doses.

The Insect Circulatory System: Structure, Function, and Evolution

“…Several neurotransmitters modulate the heart contraction rate (59). Serotonin and octopamine are cardioacceleratory; glutamate is cardioacceleratory in some insects and has no effect or conflicting effects in others (22,27,61,66,108,178). Octopamine may regulate heartbeat reversals, and glutamate has been implicated in the retrograde pacemaker of fruit flies but not mosquitoes (27,61,98).…”

Atividades farmacológicas e biológicas da peçonha de Micrurus surinamensis (cobra coral semi-aquática)

“…Vertebrados e invertebrados apresentam processos fisiológicos distintos, especialmente no que diz respeito àqueles de importância vital. Desta forma, os efeitos de peçonhas também tendem a apresentar efeitos divergentes e distintos entre vertebrados e invertebrados [201]. A toxicidade de peçonhas e toxinas isoladas de serpentes elapídicas já foi avaliada em diferentes modelos de insetos.…”

“…Um efeito cronotrópico positivo é observado com a administração de serotonina (principal modulador), dopamina, triptamina, sinefrina, octopamina e ACh, sendo que a dopamina exerce sua função provavelmente por ação neurogênica. A frequência cardíaca é reduzida com um análogo da xilamidina (antagonista de receptores 5-HT 1A e 5-HT 2A ), reforçando a importância da via serotoninérgica para o sistema [201].…”