Responses of mean arterial pressure to pressor agents and diuretics in renal hypertensive and salt hypertensive rats.

1. The responses of the mean arterial pressure to (-)-noradrenaline, tyramine, angiotensin II-val(5)-amide, vasopressin and rat renin have been contrasted in renal hypertensive and in salt plus desoxycorticosterone hypertensive rats. The responses were measured in rats both unanaesthetized and rats anaesthetized with pentobarbitone.2. Responses of unanaesthetized, ganglion blocked renal hypertensive rats to noradrenaline, tyramine and vasopressin markedly exceeded, and to angiotensin II and renin were markedly smaller than, those of unanaesthetized ganglion blocked salt + DOC hypertensive animals. Responses to angiotensin and to renin were apparently enhanced in the latter animals.3. Hydrochlorothiazide and frusemide markedly reduced mean arterial pressure in salt + DOC hypertensive rats before and after ganglionic blockade.4. Neither diuretic caused significant reduction in the mean arterial pressures of unanaesthetized, renal hypertensive rats in the absence of ganglionic blockade: frusemide did so in anaesthetized and unanaesthetized rats after ganglionic blockade.5. Whereas the diuretics did not affect the responses of the renal hypertensive rats to pressor agents, frusemide and to a lesser extent hydrochlorothiazide tended to depress the responses to pressor agents in salt induced hypertension.6. Hydrochlorothiazide did not influence mean arterial pressure in unanaesthetized rats with neurogenic hypertension.