Nociception in chicken embryos, Part I: Analysis of cardiovascular responses to a mechanical noxious stimulus

Abstract

While it is assumed that chicken embryos acquire the ability for nociception during the developmental period in the egg, an exact time point has not yet been specified. This study aimed to determine the onset of nociception during embryonic development in chicken. Changes in blood pressure and heart rate (HR) in response to a mechanical noxious stimulus at the base of the beak versus a light touch on the beak in chicken embryos between embryonic days (EDs) 7 and 18 were examined. Mean arterial pressure (MAP) was the most sensitive parameter for assessing cardiovascular responses. Significant changes in MAP in response to a noxious stimulus were detected in embryos at ED16 to ED18, while significant changes in HR were observed on ED17 and ED18. Infiltration anesthesia with the local anesthetic lidocaine significantly reduced reactions in MAP on ED18, so the cardiovascular changes can be assumed to be nociceptive responses.