Presynaptic modulation of K+-evoked [3H]dopamine release in striatal and frontal cortical synaptosomes of normotensive and spontaneous-hypertensive rats.

Regional differences in presynaptic [3H]dopamine ([3H]DA) release and its modulation by D2 DA-receptors between the frontal cortex and striatum obtained from Wystar-Kyoto (WKY) and spontaneous-hypertensive rats (SHR) have been evaluated using superfused synaptosomes. Synaptosomal tritium content was significantly lower in the frontal cortex than in the striatum in both SHR and WKY (approximately 45% and 48%, respectively), but no differences in tritium content were obtained between strains. However, the 15 mM K+-evoked [3H]DA overflow was lower in the SHR as compared to WKY rats in both brain regions (striatum approximately 23%, frontal cortex approximately 21). Concentration-response curves for quinpirole (1nM-10 microM)-mediated inhibition of 15mM K+-evoked [3H]DA release showed no differences between SHR and WKY. These results suggest that SHR has less ability to release [3H]DA as compared to WKY rats, but SHR did not show differences in the autoregulation of such release in both the frontal cortex and striatum.