Long Term Control of BP Flashcards
What did McCubbin 1956 show?
Cellophane wrapped dog kidney (perinephritic hypertension). At any pressure CSN firing less in hypertensive dog cf normal. At 60mmHg, there is a burst of firing with each cardiac cycle in the normal dog, but hypertensive is silent. Thus, baroreceptor mechanisms appear to be reset at the higher pressure levels of the the dog with chronic hypertension. Their ability to buffer changes in arterial pressure remains, consequently, they would tend to maintain rather than inhibit the chronic phase of renal hypertension.
What did Cowley, Liard, Guyton show in 1973?
Denervated then stripped adventitia around both carotid sinuses and AA, painted them with 5% phenol and isopropyl alcohol. They also cut left cervicovagus trunk and the medial bundle of the right vagus. This produced sinoaortic denervated (SAD) animals.
SAD dogs showed greater diurnal variation and after 40 days had settled at 10mmHg greater than control.
Problems with Cowleys work?
Size of the mean BP dependent on housing conditions. Variations and mean BP increase following SAD is much smaller if quiet and calm environment.
Based on a “typical” dog, often quoted. Really typical?
Was the change in BP (roughly 10mmHg) really that non-existent as made out? Should the data have been collected in a more “normal” environment?
What did Persson et al, 1989 show?
Cardiopulmonary-R could compensate for loss of arterial baro-R.
Other animal work on SAD models?
Baboons - large increase in mean BP, that falls to a new level which is higher by 11mHg than intact animals and is maintained for at least 4 weeks.
Rat - little change mean BP but SAD was assoc with large rises in mean BP in salt challenged diet with greater diurnal variation.
What is the problem with SAD?
The body may learn to adapt to not having baro-R input over that time period. Eg, if someone breaks their wrist, they learn to use their other hand.
It also removes the tonic input from Baro-R to NTS, a very abnormal state.
When should results be collected?
What environment should the animals be kept in?
