Two routes of continuous amphetamine administration induce different behavioral and neurochemical effects in the rat

Continuous amphetamine administration has proven to be a useful pharmacological tool. The two systems popularly used for the continuous administration of amphetamine differ in their release characteristics; output of drug from passive diffusion silicone-tubing implants gradually declines over several days, while that osmotically driven, active pumps remain more stable over time. A matched-dose comparison of the behavioral and neurochemical effects of both systems was performed in which silicone pellets and pumps were filled with appropriate concentrations of drug so as to release equal total quantities over the test period of 5 days. Rat behavior and brain catecholamine levels were affected in quantitatively and qualitatively different ways. The interesting constellation of behavioral and neurochemical changes associated with the use of silicone-tubing systems for the continuous administration of amphetamine may not be confounded by its declining output, but rather caused by it.