Behavioral effects and cerebral pharmacokinetics of apomorphine in the rat: dependence upon the route of administration.

Effect of the route of administration and satiation on behavioral effects of apomorphine and its pharmacokinetics in the brain was studied in the rat. The highest brain concentration and the strongest behavioral response (gnawing) were observed after a subcutaneous injection of the drug to fasted rats. Intraperitoneal injections produced a more rapid onset of apomorphine action, but lower cerebral concentration of the drug. Intracerebroventricular injections produced a weak effect. Apomorphine administered systemically was eliminated from the brain according to equations for a two-compartment model; the possibility that the long half-time compartment represents the receptor bound apomorphine is discussed. After intracerebroventricular injections apomorphine was eliminated according to equations for the one-compartment open model: the elimination of the drug from the cerebrospinal fluid to circulation was rapid (half-time approx. 9 min).