Differential Effect of Morphine and Morphine-6-glucuronide on the Control of Breathing in the Anesthetized Cat

Abstract

In anesthetized cats, the mu-opioids morphine and M6G induce respiratory depression at different sites within the ventilatory control system. Because 3mNTX caused full reversal of the respiratory depressant effects of both opioids, it is unlikely that a 3mNTX-sensitive unique M6G receptor is the cause of the differential respiratory behavior of morphine and M6G.

Naloxone Reversal of Morphine- and Morphine-6-Glucuronide-induced Respiratory Depression in Healthy Volunteers

“…A unique M6G receptor has been postulated previously, 18 but we were unable to demonstrate its existence in an animal model of M6G versus morphineinduced respiratory depression. 19 Shafer et al 20 postulated that if a drug would act at several targets in the signaling cascade, this would increase the apparent potency as well as the value of the steepness parameter ␥. We added a steepness parameter to describe the data adequetly.…”

The effects of a single mild dose of morphine on chemoreflexes and breathing in obstructive sleep apnea

“…Elevated CO 2 threshold by opioids have been inferred in previous human and animal studies using indirect estimate of 2 CO P threshold by extrapolating ventilatory response slope line (Berkenbosch et al, 1994;Lalley, 2004;Teppema et al, 2008). Morphine (Berkenbosch et al 1994), M6G (Teppema et al, 2008) and fentanyl (Lalley, 2004) were found to increase estimated 2 CO P threshold in cats. The effect has also been reported in a human study through observing of a right shift of the steady-state CO 2 response curve with morphine injection (Bourke and Warley, 1989).…”

Effect of Three Anesthetic Induction Protocols on Laryngeal Motion during Laryngoscopy in Normal Cats

“…Selective agonists of Mu‐opioid receptors are widely used to provide perioperative analgesia and their use alone or in combination with sedatives is well documented. Opioids generally cause dose‐dependent respiratory depression; however, methadone administered before surgery provides effective analgesia without adverse behavioral, respiratory, or cardiovascular side effects . Propofol allows rapid induction of anesthesia, but apnea can be induced by rapid IV administration .…”