The influence of midazolam on heart rate arises from cardiac autonomic tones alterations in Burmese pythons, Python molurus

Author(s)

Lopes, Iva Guidini ^[1] ; Armelin, Vinicius Araujo ^{[2, 3]} ; da Silva Braga, Victor Hugo ^{[3, 4]} ; Florindo, Luiz Henrique ^{[1, 3, 4]}

Affiliation

^[1] Sao Paulo State Univ UNESP, Aquaculture Ctr CAUNESP, Via Prof Paulo Donato Castellane, N-N, BR-14884900 Jaboticabal, SP - Brazil

^[2] Fed Univ Sao Carlos UFSCar, Dept Physiol Sci, Via Washington Luiz, Km 235, BR-13565905 Sao Carlos, SP - Brazil

^[3] CNPq, INCT FAPESP, Natl Inst Sci & Technol Comparat Physiol, Via 24A, 1515, BR-13506900 Rio Claro, SP - Brazil

^[4] Sao Paulo State Univ UNESP, Dept Zool & Bot, Cristovao Colombo St 2265, BR-15054000 Sao Jose Do Rio Preto, SP - Brazil

• Document type: Journal article
• Source: AUTONOMIC NEUROSCIENCE-BASIC & CLINICAL; v. 208, p. 103-112, DEC 2017.
• Web of Science Citations: 6

Abstract

The GABAA receptor agonist midazolam is a compound widely used as a tranquilizer and sedative in mammals and reptiles. It is already known that this benzodiazepine produces small to intermediate heart rate (HR) alterations in mammals, however, its influence on reptiles' HR remains unexplored. Thus, the present study sought to verify the effects of midazolam on HR and cardiac modulation in the snake Python molurus. To do so, the snakes' HR, cardiac autonomic tones, and HR variability were evaluated during four different experimental stages. The first stage consisted on the data acquisition of animals under untreated conditions, in which were then administered atropine (2.5 mg kg(-1); intraperitoneal), followed later by propranolol (3.5 mg kg(-1); intraperitoneal) (cardiac double autonomic blockade). The second stage focused on the data acquisition of animals under midazolam effect (1.0 mg kg(-1); intramuscular), which passed through the same autonomic blockade protocol of the first stage. The third and fourth stages consisted of the same protocol of stages one and two, respectively, with the exception that atropine and propranolol injections were reversed. By comparing the HR of animals that received midazolam (second and fourth stages) with those that did not (first and third stages), it could be observed that this benzodiazepine reduced the snakes' HR by 60%. The calculated autonomic tones showed that such cardiac depression was elicited by an 80% decrease in cardiac adrenergic tone and an 620% increase in cardiac cholinergic tone a finding that was further supported by the results of HR variability analysis. (AU)

• FAPESP's process: 08/57712-4 - The National Institute of Comparative Physiological Research
• Grantee: Augusto Shinya Abe
• Support Opportunities: Research Projects - Thematic Grants