Decreased responsiveness of the aortae of hypertensive rats to acetylcholine, histamine and noradrenaline

1 The responses to noradrenaline (NA) of the aortae of various hypertensive rats, namely the spontaneously hypertensive rat (SHR), the low blood pressure SHR (LBP‐SHR), and the left renal artery stenosed LBP‐SHR (LRAS‐LBR‐SHR), were compared to those of the normotensive Wistar‐Kyoto rats (WKY). 2 The aortae of the hypertensive rats were significantly more responsive (P LBP‐SHR > SHR> LRAS‐LBP‐SHR with the corresponding maximal tension (g) 0.89 ± 0.04, 0.59 ± 0.04, 0.36 ± 0.04, 0.19 ± 0.05. 5 The results suggested that elevation of blood pressure above the normal (due either to intrinsic or extrinsic factors), as seen in SHR and LRAS‐LBP‐SHR, results in a decreased response of the aortae to ACh and histamine. This effect was seen in both the endothelium mediated relaxation and the non‐endothelium mediated contraction.