1. Salt loading accelerates and increases the rise in blood pressure (spSH) in stroke-prone spontaneously hypertensive rats, but not in Wistar-Kyoto (WK) rats.
2. In both strains a slight increase in plasma volume was obtained during salt loading.
3. Salt loading caused a distinct increase in plasma noradrenaline concentration in spSH rats, but a slight decrease in WK rats. Plasma adrenaline and dopamine concentrations remained unaffected.
4. Exposure to cold resulted in a more marked stimulation of sympathoadrenal and sympathoneuronal activity in salt-loaded spSH rats than in spSH rats on a normal sodium diet.
5. It is concluded that salt loading results in a further increase of the already elevated sympathetic activity in spSH rats.