 Perhaps, both might be involved in opioid addiction and opioid-induced deficits in cognition.Activation of the μ-opioid receptor by an agonist such as morphine causes analgesia, sedation, slightly reduced blood pressure, itching, nausea, euphoria, decreased respiration, miosis (constricted pupils), and decreased bowel motility often leading to constipation.Some of these effects, such as analgesia, sedation, euphoria, itching and decreased respiration, tend to lessen with continued use as tolerance develops.