Effects of the antihypertensive drugs Ó-methyldopa and hydralazine on the performance of spontaneously hypertensive rats in the elevated plus-maze

ABSTRACT

The effects of antihypertensive drugs on the performance of spontaneously hypertensive rats (SHR) in the elevated plus-maze were determined. Male SHR (3 months old) were submitted to long-term treatment (15 days) with Ó-methyldopa (ÓMD, 5g/l, N = 10) and hydralazine (HYD, 100 mg/l, N = 10) given orally, diluted in water. After the drug treatment, the performance of the rats in the plus-maze was observed for 5 min in a single test and mean arterial pressure (MAP) and heart rate (HR) were then measured. The antihypertensive drugs reduced MAP significantly (mean ñ SEMCON = 176.2 ñ 5.2, ÓMD = 157.8 ñ 4.6 and HYD = 150 ñ 4.4 mmHg) and only ÓMD increased HR significantly (mean ñ SEMCON = 391.7 ñ 13.8, ÓMD = 453.3 ñ 14 and HYD = 368.8 ñ 18.9 bpm). The ÓMD group presented a lower total number of entries (mean ñ SEMCON = 12.7 ñ 0.7, ÓMD = 8.7 ñ 0.9 and HYD = 12 ñ 0.9) and spent less time in the open arms than the CON (N = 10) and HYD groups (mean ñ SEMCON = 0.69 ñ 0.04, ÓMD = 0.48 ñ 0.07 and HYD = 0.65 ñ 0.06 s). ÓMethyldopa acts centrally and hydralazine acts peripherally. The behavioral change of SHR treated with Ó-methyldopa suggests that hypertension seems to be related to central nervous dysfunctions that are affected by an antihypertensive drug with central noradrenergic action