A administração oral de 15, 30 e 60 mg/kg de l-hexil-3,7-dimetilxantina produziu, em cães, dilatação dos vasos piais sem ocasionar hipotensão arterial.

The authors studied the action of the l-hexyl-3,7-dimethylxanthine on the blood pressure and on the caliber of the pial vessels of the dog. In 15 dogs anesthetized by sodium penthobarbital (30 mg/kg) the arterial blood pressure was recorded with a mercury manometer. The pial vessels were observed through a window made in the temporal bone with the aid of binocular stereoscopic microscope. For photography one of the oculars of the microscope was replaced by an appropriate camera. The procedure was that proposed by Forbes4 modified by Melaragno5. Groups of 4 animals received respectively 15, 30 and 60 mg/kg of the drug by the oral route and were observed until 240 minutes. The other three animals were used as control and observed by the same interval of time, receiving only the anesthetic. The oral administration of the l-hexyl-3,7-dimethylxanthine induced marked relaxation of the pial vessels without concomitant fall of the arterial blood pressure, in spite of the doses of 15 mg/kg.

A perfusão com Tyrode a 39°C não ocasionou modificações apreciáveis das temperaturas cerebral e retal. Da mesma forma, não se observaram alterações pronunciadas da respiração e da pressão arterial. As seguintes alterações foram verificadas com a perfusão a 0°C: a) A temperatura cerebral baixou gradativamente até o nível mínimo de 21°C. b) A temperatura retal não foi influenciada pela perfusão fria. As eventuais diminuições observadas, podem ser atribuídas à anestesia, pois ocorreram em cães utilizados para contrôle e, por outro lado, o aquecimento do animal preveniu a referida queda de temperatura, c) Depressão e/ou parada respiratória foram fenômenos observados de maneira constante em tôdas as perfusões. A depressão respiratória ocorreu mesmo com temperatura cerebral ao redor de 30°C. Reiniciadas as perfusões a 39°C, houve pronta recuperação respiratória, d) Bradicardia, suscetível de ser inibida pela atropina, foi verificada em 3 animais, acompanhando-se de hipotensão arterial. Entretanto, as respostas tensionais foram variáveis: hipotensão ou hipertensão, e) Elevação da temperatura cerebral (com tendência a valôres normais), durante a perfusão fria, foi observada em alguns animais. Conquanto não se possa, ainda, explicar convenientemente o fato, talvez decorra de vasodilatação secundária, f) Em 2 animais ocorreu parada cardíaca, passível de tratamento pela adrenalina.

Dogs were anesthetized with sodium pentobarbitone (30 mg/kg, intravenously). After tracheotomy, the record of the arterial blood pressure was performed, in the femoral artery. The lateral branch of the tracheal cannula was attached to a Marey apparatus. A cannula was planted in the lateral ventricle and other in the cisterna magna. A electrode was also planted in the brain to record the encephalic temperature. Also, the rectal temperature was recorded. The perfusion was performed with Tyrode solution at 0°C or 39°C. The perfusion at 39°C did not change the brain or rectal temperature. The following modifications were verified with perfusion at 0°C: a) The cerebral temperature decreased until 21°C. No changes were observed in the rectal temperature, b) Respiratory arrest, reversible when the brain was warmed with perfusion at 39°C. c) Vagal stimulation, with fall of blood pressure and bradycardia, which was abolished by atropine.