2.14.1 Drugs
Morphine sulfate (Hospira, Inc., Lake Forest, IL) and the peripherally acting mu-opioid agonist DALDA (US Biological Life Sciences, Salem, MA) were diluted with normal saline and injected subcutaneously at 5 mg∙kg-1. Isoflurane (Sigma, St. Louis, MO) mixed in 2.5 l∙min-1 oxygen was delivered through a nose cone to induce and maintain anesthesia and ensure the welfare of animals during surgical procedures. All drugs were weighed and prepared fresh prior to use. Drug doses were determined by their ED50 and are in line with our previous studies (Tiwari et al., 2018).