PSYC 207 Lecture Notes - Lecture 22: Opioid Antagonist, Pupillary Response, Partial Agonist
Document Summary
Opioids are injected into the vta which increases dopamine release in the nacc. B-endorphin injections produces similar enhancement of vta firing neurons. K-agonists produce the opposite effect and reduce dopaminergic activity - can cause conditioned place aversions and dysphoria. Also interacts with da system to regulate aversively motivated behaviours. Rush: initial and rapid onset of euphoria. Straight: period of normalcy between craving opioids and feeling euphoric. Pleasurable effects develop tolerance quickly while constipation pupillary dilation are slower. Opioids depress cns function; a rebound hyperactivity. Withdrawal symptoms are not life threatening but very unpleasant. Worst on 2&3rd day, gone by the 7th. Severity and duration of symptoms depends on type of opioid used. In cell cultures with opioid receptors, morphine inhibits camp. Removing morphine or adding opioid antagonist naloxone leads to a rebound increase in camp levels. Naloxone is used to induce withdrawal symptoms during detox - increases severity of of withdrawal symptoms but also shortens duration.
