Parker and Radow test of drug withdrawal aversion: opposite effect in rats chronically infused with sufentanil or amphetamine

In rats, cessation of periodic injections of morphine reduces a preference for a palatable saccharin solution presented in a choice with water, and this has been interpreted to reflect withdrawal malaise. We confirmed and examined this "Parker and Radow Model" using subcutaneously implanted osmotic minipumps as the means of drug delivery and the opiate, sufentanil, and the psychostimulant, amphetamine, as the treatment drugs; surgical removal of the pumps was used to initiate withdrawal. Thus, rats withdrawn after 2 weeks exposure to a sufentanil-delivering pump (0.25 microgram/hr) showed a decreased preference for the saccharin and animals exposed to an amphetamine pump (68 micrograms/hr) showed an increased preference, as compared to placebo-exposed controls. This pattern of effects was systematically replicated in new subjects using 4 weeks of treatment and 136 micrograms/hr amphetamine. Since the locomotor increasing and body weight decreasing effects of amphetamine were also demonstrated and the doses of amphetamine and sufentanil were in comparable dose ranges, it was concluded that the Parker and Radow procedure may be a reliable measure of opiate withdrawal, but under similar test and treatment conditions other processes may be operative in amphetamine-treated animals. Problems of measuring motivation of withdrawal, particularly of spontaneous withdrawal, were noted.