We examined monoamine contents in various regions of the brain and catecholamine contents in the heart and the adrenal gland of stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto (WKY) rats aged 1.5, 3 and 6 months. 2. The noradrenaline (NA) content and the 5-hydroxytryptamine (5-HT) content in the brainstem were larger in 1.5 month old SHRSP than in the age-matched WKY. In addition, at age 6 months the brainstem 5-HT content was higher in SHRSP than in WKY. 3. The NA and 5-HT contents in basal ganglia, thalamus, hypothalamus, septum and anterior and lateral cerebral cortex showed no significant difference between SHRSP and WKY at any age. 4. The dopamine (DA) contents in all brain regions examined did not differ between WKY and SHRSP at any age. 5. The NA contents in left and right ventricles were larger in 3 month old SHRSP than in the age-matched WKY, but were lower in 6 month old SHRSP than in the age-matched WKY. The cardiac DA contents did not differ between the two rat strains of any age. 6. The adrenal NA and adrenaline (A) contents in 6 month old SHRSP were significantly larger than those in the corresponding WKY. 7. These findings suggest that the increased NA and 5-HT contents in the brainstem may be related to the onset of hypertension, and that the altered cardiac NA contents and adrenal NA and A contents change as a result of the onset or persistence of hypertension.
