Cardiovascular reactivity as a learning indicator in the amphibian Rhinella arenarum

Abstract

In vertebrates, adaptation to new environments involves cardiorespiratory adjustments, especially when faced with an aversive one. In order to understand the mechanisms that control these phenomena, we have developed a procedure for aversive stimulation and chronic recording of cardiac activity in the Rhinella arenarum toad.The subjects were implanted with electrodes secured with clips and exposed to the presentation of NaCl solutions in an inescapable compartment, while the heart rate was recorded on a PC with a polygraph. I train them once a day for 12 sessions. First 6 sessions of Acquisition and then 6 of Extinction. During the acquisition, a 300 mM NaCl saline solution (neutral) was presented, followed by an 800 mM NaCl solution (aversive) which generated a large increase in heart rateWith the succession of Acquisition tests, this reactivity was registered upon presentation of the neutral solution, showing an anticipatory tachycardia to the aversive event. During extinction, the aversive solution was replaced by a neutral one, which led to the disappearance of this anticipatory cardiovascular response.These results would indicate a physiological adjustment of the cardiovascular system mediated by a learned response, probably part of an adaptive system to cope with threatening situations.