Elevation of blood pressure as the basis for discriminative stimuli produced by methoxamine

Male, hooded rats were trained to detect methoxamine using a discrimination paradigm in which responding under an FR10 schedule was reinforced on one lever following an injection of methoxamine (1.25 mg/kg) and on an alternate lever following an injection of saline. The rats learned the methoxamine‐saline discrimination to a criterion of correct lever selection on 10 consecutive days in an average of 35 training sessions. In subsequent tests, selection of the methoxamine‐appropriate lever was found to be both time dependent and dose dependent, and these effects closely paralleled time‐ and dose‐related increases in systolic blood pressure. In addition, the ability to increase blood pressure was a common property of those drugs that substituted for methoxamine in the discrimination test. These findings suggest that interoceptive stimuli related to elevated blood pressure provide the basis for methoxamine discrimination. Drug discrimination paradigms may, therefore, be useful within programs for management of hypertension, as a method for enhancing conscious awareness of blood pressure changes.