Studies with PKCε knockout mice indicate that PKCε regulates sensitivity to opiates. PKCε knockout mice develop self-administration of morphine at a lower dose and show a greater analgesic response to morphine than wild-type mice.221 It is not known whether the magnitude of self-administration is different at higher doses. Therefore, PKCε reduces acute sensitivity to opiates, but it is not yet known if PKCε alters the reinforcing properties of opiate drugs.
