RESUMO
Mammalian and reptilian vascular tissues present basal release of 6-nitrodopamine, which is reduced when the tissues are pre-incubated with the NO synthase inhibitor L-NG-Nitro arginine methyl ester (L-NAME), or when the endothelium is mechanically removed. 6-Nitrodopamine induces vasorelaxation in pre-contracted vascular rings by antagonizing the dopaminergic D2-like receptor. Here it was investigated whether male swine vessels (including carotid, left descendent coronary, renal, and femoral arteries) release 6-nitrodopamine, dopamine, noradrenaline, and adrenaline, as measured by liquid chromatography coupled to tandem mass spectrometry. The in vitro vasorelaxant action of 6-nitrodopamine was evaluated in carotid, coronary, renal, and femoral arteries precontracted by U-46619 (3 nM), and compared to that induced by the dopamine D2-receptor antagonist L-741,626. Expression of tyrosine hydroxylase and the neuromaker calretinin was investigated by immunohistochemistry. All vascular tissues presented basal release of endothelium-derived catecholamines. The relaxation induced by 6-nitrodopamine was not affected by preincubation of the tissues with either L-NAME (100 µM, 30-min preincubation) or the heme-site inhibitor of soluble guanylyl cyclase ODQ (100 µM, 30-min preincubation). Electrical field stimulation (EFS)-induced contractions were significantly potentiated by previous incubation with L-NAME, but unaffected by ODQ preincubation. The contractions induced by EFS were reduced by preincubation with either 6-nitrodopamine or L-741,626. Immunohistochemistry in all arteries revealed the presence of tyrosine hydroxylase in the endothelium, whereas immunoreactivity for calretinin was negative. Swine vessels present basal release of endothelium-derived catecholamines and expression of tyrosine hydroxylase in the endothelium. The vasodilation induced by 6-nitrodopamine is due to blockade of dopaminergic D2-like receptors.
RESUMO
Resumo Resultados nulos, negativos ou inesperados são ocorrências possíveis para pesquisadores em todo o mundo. Não publicar tais resultados representa desperdício de recursos (de tempo, dinheiro e esforços). O objetivo deste estudo foi avaliar, mediante aplicação de questionário, o que estudantes de medicina e médicos pensam sobre a publicação de resultados inesperados ou negativos em pesquisa e discutir os aspectos éticos da questão. As questões foram respondidas por 40 alunos e 30 médicos de uma faculdade privada de medicina. Conclui-se que ainda é pouco discutida e aceita a publicação de resultados negativos ou inesperados, persistindo a crença que publicar tais resultados pode prejudicar a reputação dos pesquisadores. Quase todos os participantes acreditam ser importante a publicação desse tipo de resultados, mas apenas cerca de 60% os publicariam. Torna-se, então, importante e necessário ampliar a discussão sobre o assunto nas escolas médicas para se criar nova mentalidade acadêmica.
Abstract Null, negative or unexpected results are possible occurrences for researchers around the world. Not publishing such results is a waste of resources (time, money, and effort). The objective of this study was to evaluate, through a questionnaire, what medical students and physicians thought about the publication of unexpected or negative results in research and to discuss the ethical aspects of the matter. The questions were answered by 40 students and 30 physicians from a private medical school. It is concluded that the publication of negative or unexpected results is still insufficiently discussed and accepted, perpetuating the belief that publishing such results may harm the researchers' reputation. Almost all participants believe it is important to publish these kind of results, but only about 60% of them would publish such results. It is therefore important and necessary to broaden the discussion on this subject in medical schools to create a new academic mindset.
Resumen Los resultados nulos, negativos o inesperados son acontecimientos posibles para los investigadores en todo el mundo. No publicar tales resultados representa un desperdicio de recursos (de tiempo, dinero y esfuerzos). El objetivo de este estudio fue evaluar, a través de la aplicación de un cuestionario, qué piensan los estudiantes de medicina y los médicos sobre la publicación de resultados inesperados o negativos en la investigación y discutir los aspectos éticos de la cuestión. 40 alumnos y 30 médicos de una facultad privada de medicina respondieron al cuestionario. Se concluye que aún es poco discutida y aceptada la publicación de resultados negativos o inesperados, persistiendo la creencia de que publicar tales resultados puede perjudicar la reputación de los investigadores. Casi todos los participantes creen que es importante la publicación de este tipo de resultados, pero solo el 60% de ellos los publicaría. Se hace importante y necesario, entonces, ampliar la discusión sobre este tema en las facultades médicas para crear una nueva mentalidad académica.