[Central dopaminergic function in stroke-prone spontaneously hypertensive rats (SHRSP): I. Alteration of locomotor activity and swimming ability].

The possible alteration of central dopaminergic (DA) function, which accompanies the development and persistence of hypertension, was studied in SHRSP by measuring the lisuride-induced locomotor activity and the swimming ability. 1) When administered at a dosage of 50 micrograms/kg, lisuride, a DA agonist, induced significant increases of the locomotor activity in one- and 2-month-old Wistar Kyoto rats (WKY), but not in the 6 month-old rat. Differing from the response of WKY, SHRSP showed only a moderate increase in the locomotor activity at the age of one month (means of systolic blood pressure: 128 mmHg) and apparently no increase at the age of 2 months (176 mmHg). In 6 month-old SHRSP (238 mmHg), hypomotility but not hypermotility was induced by the lisuride administration. 2) Though no significant difference was detected at the age of 4 months, the swimming ability of SHRSP at the age of 8 months was deteriorated significantly as compared to that of WKY, and the impaired swimming performance of SHRSP was improved by the administration of lisuride. These results indicate that some alterations in the synaptic sites of the central DA neuron occurred already at an early stage of the hypertensive development, followed under persistent hypertension by the progressive deterioration of the motor-coordination ability as detected in the swimming ability.