Proven cardiac changes during death-feigning (tonic immobility) in rabbits (Oryctolagus cuniculus)

Abstract

Tonic immobility (TI) is a response to fear or threat by remaining motionless, principally when attacked by predators from which there is no possibility of escape. Thus, here we demonstrate a way of easily reproducing this phenomenon in a laboratory setting and characterize the cardiac electromechanical alterations during TI. We observed a significant decrease in heart rate (HR) and changes of rhythm in electrocardiogram during TI in rabbits. Echocardiogram showed a significant increase in the left ventricle chamber diameter during systole and a consequent decrease in fractional shortening and ejection fraction, in addition to the HR and rhythm changes. There was also a significant decrease in aortic and pulmonary artery blood flow. Diastolic functional changes included a significant decrease of the peak atrial contraction velocity (A peak) and consequent increase in the ratio of peak early diastolic velocity to A peak and increased isovolumetric relaxation time. We were able to prove that TI changes the cardiac function considerably. Although the "fight-or-flight" response is the most common response to fear, which is characterized by the action of sympathetic nervous system with tachycardia and increased physical activity, TI is an alternative anti-predator behavior causing cardiac changes opposite to the "fight-or-flight" phenomenon.

Effects of starvation on death‐feigning in adult Eucryptorrhynchus brandti (Coleoptera: Curculionidae)

“…antipredation behaviour, death-feigning intensity, defence, starvation duration, survival strategy, weevil is approximately 50% of that in the normal state (Giannico, Lima, Lange, Froes, & Montianiferreira, 2014). In the absence of further stimulation, after a few minutes or more, the death-feigning insect wakes up and escapes.…”

“…Eucryptorrhynchus scrobiculatus completely contracts its beak, and wireworms bend their bodies (Meng & Liang, ). Physiological changes associated with thanatosis are unique; the respiratory rate is close to zero, the heart rate decreases by 33%, on average, and the metabolic rate is approximately 50% of that in the normal state (Giannico, Lima, Lange, Froes, & Montianiferreira, ). In the absence of further stimulation, after a few minutes or more, the death‐feigning insect wakes up and escapes.…”

Non-invasive evaluation of placental blood flow: lessons from animal models

“…In rabbits (Polisca et al 2010), bitches and queens (Nautrup 1998, Di Salvo et al 2006, Scotti et al 2008, Giannico et al 2014, normal ranges of UtA and UmA blood flow parameters have been detailed throughout pregnancy, as well in mice using high-frequency ultrasound (Hernandez-Andrade et al 2014). In both rabbits and mice, they were also used to compare functional haemodynamic changes of the placenta in pathophysiologic conditions (Venditti et al 2013, Lopez-Tello et al 2015, Valentino et al 2016.…”

Theory of Mind: Towards an Evolutionary Theory

“…38 Despite its reflexive nature TI is not easy to fit into the sympatheticparasympathetic dichotomy. There are, for instance, conflicting results concerning heart function with some studies finding increases in heart rate and others finding decreases (Davie et al 1993;Valance et al 2008;Giannico et al 2014). On account of its opposition to the fight-or-flight reflex, its cholinergic neurotransmission and general passivity I prefer to place it on the parasympathetic side.…”