Proceedings of The Physiological Society

University of Manchester (2010) Proc Physiol Soc 19, PC190

Poster Communications

Myogenic responses of cremaster small arteries from the Brown Norway rat

A. Izzard1, P. J. Delaney1, M. P. Burnham1, A. M. Heagerty1

1. Cardiovascular Research Group, University of Manchester, Manchester, United Kingdom.

The Brown Norway (BN) rat is susceptible to hypertension-induced cerebral haemorrhage whereas the Long Evans (LE) rat is not. Our in vitro studies have shown that the myogenic response (which is an active constriction in response to an increase in intraluminal pressure) of middle cerebral arteries from the BN rat are impaired, compared with those of the LE rat, and this may explain the susceptibility to cerebral haemorrhage1. The aim of the current study was to determine whether an impaired myogenic response is also observed in systemic small arteries from BN rats, compared with LE rats. Cremaster arteries from rats aged 14-18 wk were studied. Following killing, the cremaster muscle was removed and placed in ice cold physiological salt solution (PSS) A segment of artery was dissected and the ends tied onto glass cannulae in an arteriograph chamber (Living systems), pressurised to 80 mmHg and superfused with PSS gassed with 5% CO2 in air at 340C. Lumen diameter was continually recorded using a video dimension analyser (Living Systems). After the development of spontaneous myogenic tone, intraluminal pressure was reduced to 20 mmHg and then increased in 20 mmHg increments up to 200 mmHg. This procedure was repeated in calcium-free PSS to determine the passive pressure-diameter relationship. The results showed that between 60 and 160 mmHg, steady state diameter at a higher pressure was less than or equal to the diameter at the previous lower pressure in the presence of myogenic tone for arteries from both BN and LE rats, demonstrating an identical pressure range of myogenic responses between strains. Arterial diameter did not differ between strains within this pressure range; beyond this pressure range forced dilation was observed in arteries from BN rats only. At 60 mmHg arterial diameter was 128 ± 10 v 115 ± 9 (N.S) and at 160 mmHg arterial diameter was 87 ± 6 v 86 ± 8 (N.S) BN and LE respectively, n=10 in each group. These results demonstrate that, unlike middle cerebral arteries, the myogenic responses of cremaster arteries from the BN rat do not differ from the LE rat across a wide pressure range.

Where applicable, experiments conform with Society ethical requirements