Effects of six antihypertensive drugs on blood pressure and hypothalamic GABA content in spontaneously hypertensive rats

In order to investigate the effects of antihypertensive drugs on blood pres sure and gamma -amino butyric acid (GABA) content in the hypothalamus and t he possible relationship between blood pressure decrease and GABA content c hanges. blood pressure and GABA contents after chronic (20 weeks) treatment s of nitrendipine, atenolol, captopril, hydrochlorothiazide, dihydralazine and prazosin were studied in spontaneously-hypertensive rats (SHR). The acu te and subacute (1 week) effects of nitrendipine on GABA contents was also observed in SHR. It was found that 20 week treatments with six different an tihypertensive agents produced a decrease in systolic blood pressure and an increase in GABA. content. The blood pressure level was significantly corr elated with GABA content in the hypothalamus, but not with that in the cort ex. Acute treatment with a single dose of nitrendipine. did not alter GABA content. Bicuculline, a GABA receptor antagonist, did not attenuate the hyp otensive effect of nitrendipine. In conclusion, chronic treatments by diffe rent antihypertensive agents produced an increase of hypothalamic GABA cont ent and a decrease of blood pressure. The increase of GABA content induced by nitrendipine seems likely to be secondary to blood pressure decrease.