Envolvimento da neurotransmissão endocanabinóide na empatia relacionada a nocicepção em camundongos que conviveram com coespecífico em dor crônica

Abstract

Empathy is known as a sharing of emotions between individuals that allows to predict and understand their motivations, actions and feelings, crucial conditions in social life and emotional experience. Research about empathic responses can be performed through animal models, in which observe changes arising from living with a coespecific in chronic pain. These analyzes suggest changes in behavior due to this exposure, and possible pharmacological interventions can be employed to reduce such harmful responses to the subject. This study proposed to analyze, according to the empathy protocol in rodents, if the endocanabinoid neurotransmission contributed on the emission of behaviors related to anxiety and the painful perception, by the systemic administration of cannabidiol (phytocannabinoid). Male albino Swiss mice were housed in pairs for 28 days; on the 14th day, one of them got through a cirurgic procedure of chronic nerve constriction (NC) or not (SHAM). On the 28th day of cohabited, part of the animals were tested in the elevated plus maze (EPM) to assess anxiety; others were submitted to the abdominal writhing test to assess pain sensitivity. To carry out the experiments, the animals that cohabited with their coespecific CS or CNC received systemic administration of cannabidiol and were exposed to behavioral tests. In the first experiment, the observer mice was administered with subcutaneous (s.c.) injection of vehicle or canabidiol (0.3, 1.0, 10.0 and 30.0 mg/kg-1), and after 30 minutes was submited to an intraperitoneal (i.p.) injection of acetic acid (0.6%) and exposed to the whithing test. In the second experiment, the observer animal was submitted to systemic injection of vehicle or cannabidiol (0.3, 1.0, 10.0 and 30.0 mg/kg-1) and exposed to the EPM test to asses anxiety behaviours. The two ways variance analysis (cohabited x treatment) ANOVA, followed by Duncan's post hoc, has revealed that the cohabited with a conspecific in chronic pain induced an increase in behaviors related to nociception and anxiety, demonstrating the influence that cohabited with a pair in chronic pain has on the observer. In the first experiment, canabidiol at doses of 10,0 and 30,0 mg/kg has produced antinociceptive effect in the animals that lived with an CNC conspecific, what was featured by a reduction in the numbers of writhes, when compared to the CNC/vehicle conspecific. In the second experiment, canabidiol (1.0, 10.0 and 30.0 mg/kg) produced an increase in the percentage of entry into the open arms of the EPM and reduction in risk assessment behaviors, and the dose of 30.0 mg/kg produce a significant increase in the time spent in open arms, suggesting anxiolytic effect in animals that cohabited with NC conspecifics.The observed results in the present study suggest that cohabited with a conspecific in chronic pain changes the observer's emotional state; and suggest that cannabidiol may reverse the nociceptive and anxiety effects induced by cohabited with a pair in chronic pain.