Effects of some drugs on the circulatory system of the intact, non-anesthetized cephalopod, Octopus dofleini

Abstract

1. 1. The effects of epinephrine, nor-epinephrine, ergotamine, serotonin, acetylcholine, eserine, tyramine and histamine have been studied in the non-anesthetized cephalopod, Octopus dofleini. Simultaneous recordings were made of blood pressure from the aorta, the afferent and efferent branchial vessels and the large vena cava cephalica concurrent with injections of the drugs. 2. 2. Epinephrine and nor-epinephrine both had a depressing effect on the circulatory system. Both drugs caused a retardation in rate of the systemic heart. The initial effect seemed to include a decrease in the resistance of the peripheral vascular bed. The branchial hearts were also decelerated by epinephrine and nor-epinephrine. Pretreatment with dihydroergotamine abolished all effects of a subsequent injection of epinephrine. 3. 3. Tyramine, like epinephrine and nor-epinephrine, caused bradycardia of the systemic and branchial hearts. 4. 4. Acetylcholine had a marked retarding effect on the systemic heart as well as on other rhythmically contractile processes in the octopus circulatory system. To a lesser degree acetylcholine acted as a peripheral vasodilator. Histamine had a short-lasting but marked vasodilatory effect on the peripheral vascular bed. 5. 5. Serotonin invariably caused a stimulation of the systemic and branchial hearts and contractions of the ctenidia. 6. 6. The injection of the drugs demonstrated that the various functional elements in the creatly differentiated vascular system of the cephalopods influence each other via nervous communication.