Behavioral Changes Following Experimentally-Induced Acute Myocardial Infarction in Rats

Abstract

SummaryRats with experimentally-induced acute myocardial infarction (AMI) have proven to be a clinically relevant model for visceral pain. As there are no behavioral data available on rats in the postinfarction period, we aimed to identify specifi c pain-related behavioral changes following AMI to increase the validity of the model. AMI was induced by left coronary artery ligation and pain-related behavior was analyzed using the open fi eld test (OFT) and elevated plus maze (EPM). Morphine was applied following AMI induction to differentiate pain-related changes from those related to nonspecifi c global changes in responsiveness. AMI was histologically confi rmed.Hypolocomotion was consistently evident in all behavioral tests for both the infarcted group and sham group. In the OFT, both AMI and sham rats exhibited less exploratory behavior and less activity. A similar pattern of behavior was observed in EPM, where both surgical groups showed fewer entries to the open arms and spent less time in the open arms. The sham group with an intact pericardium showed the same pattern of activity as control rats. The reduction in activity and rearing observed following AMI was successfully reversed following morphine injection. This effect was abolished after naloxone application allowing us to attribute observed changes specifi cally to pain.This study demonstrates that pain-related behavior in the acute postinfarction period is generally characterized by reduced mobility and explorative behavior. Our results showed that cardiac ischemia as a consequence of experimentally-induced infarction is a less important source of pain behavior than manipulation of the pericardium. (Int Heart J 2014; 55: 169-177) Key words: Pericardium, Postoperative pain, Behavior C hest pain is the primary and the most prominent symptom leading to the hospitalization of patients with the diagnosis of acute myocardial infarction (AMI). 1)These patients account for 20% of patients in medical emergency departments.2) However, chest pain related to AMI varies signifi cantly both in its intensity 3,4) and incidence. 5,6) In addition, the pain severity does not seem to be a good predictor of the outcome of myocardial infarction. 7)While the evaluation of pain in humans is predominantly based on conscious perception, in animals it relies mainly on behavioral output. 8) Defined by the International Association for the Study of Pain (IASP) as an unpleasant sensory and emotional experience, 9) pain cannot be determined in animals, so proxy indicators are typically used. In order to increase the translational value of their studies, pain researchers working with experimental animals have focused more on complex behavioral responses and operant measures.10,11) Visceral pain models, eg, models of cardiac ischemia, delineate well these challenges. Pain elicited in these models is vague, with no specifi c region to focus pain measurements on, so broader behavioral and cognitive analysis is necessary to detect potential changes.12)The most commonly used stimuli i...

Alterations of medial prefrontal cortex bioelectrical activity in experimental model of isoprenaline-induced myocardial infarction

“…On a structural level, it was shown there is remodeling of neuronal networks in the medial PFC under the influence of stress [42]. Furthermore, according to findings of Banozic et al, anxiety like behavior can be demonstrated in a model of AMI [11]. In our current study the increase in beta band power was already significant during the first hour (H1) and remained increased during the whole four hours (D1) after isoprenaline administration.…”

“…Namely, within 72 hours of AMI onset there is neuronal loss in the central nervous system (CNS), most importantly in the lymbic system, hypothalamus and brainstem [8,9]. Further, depression onset after AMI was corroborated by studies in rats looking at behavioral signs of anhedonia and despair 2 weeks post AMI that can be reversed by antidepressants [10][11][12]. Exploring sleep-related disturbances in rats two weeks post AMI revealed decreased slow wave sleep and decreased latency to rapid eye movement (REM) sleep onset previously recognized in patients with depression [12].…”

Behavioral and molecular processing of visceral pain in the brain of mice: impact of colitis and psychological stress

“…Inflammation and psychological stress modify behavior related to emotionality, pain (Cattaruzza et al, 2013 ; Banozic et al, 2014 ) and sickness (Zhang et al, 2014 ; Farzi et al, 2015 ). Increased activity in rats exposed to unpredictable chronic mild stress resembles the psychomotor agitation seen in patients with psychiatric disorders (Gronli et al, 2005 ).…”