Effects of Age on Blood Pressure in the Chicken

Cardiovascular Pharmacology of the Domestic Fowl

“…It was further indicated that pituitary gonado trophins play an important role in the development of the sex difference, the spread in blood pressure levels between male and female chicks being governed by quantitative differences in the utilization of gonadctrophins rather than differences in the production of these hormones. As has previously been mentioned and shown in Table 2, sex dif ferences in heart rate are the opposite of those just described for blood pressure ; the pulse rate of hens being significantly higher than those of roosters (4,72,87,95). On a per kilogram weight basis, males have a significantly lower cardiac output but a higher peripheral resistance (94).…”

“…Although direct determinations of blood pressure have been made on unanesthetized chickens (7,48,50,64,(85)(86)(87)(88)(89)(90)(91)(92)(93)(94)(95)(96)(102)(103)(104), to study drug effects, it would be preferable to use anesthetized animals if only to ensure immobility and constancy of drug responses. The more common anesthetic agents which have been employed to induce general anesthesia in acute chicken experiments are sodium phenobarbital (9-15, 19, 35, 36, 41, 51, 61, 79, 80, 82, 97), sodium barbital (62), sodium amobarbital (27), sodium pentobarbital (2,25,34,41,55,66,69,100), urethane (19, 30-32, 38, 39, 73-75), morphine (104), chloral hydrate (41,49,72), chloralose (105) and ether (1, 28, 29, 38, 39, 43-45, 52, 63, 78, 104).…”

“…It shows that birds with high systolic blood pressures are better able to withstand low temperatures and severe exercise than those with low pressures (93). Blood pressure changes with age in birds appear to be unrelated to variations in pulse rate since in Sturkie's studies (95), the group of chickens with the lowest pressures had pulse rates which were significantly higher than some of the older groups with higher blood pressures. Differences in pulse rates of chickens of older age groups were not significant.…”

“…In a more recent paper (19), among chickens under phenobarbital anesthesia, roosters were found to have an average mean arterial pressure of 112 mm Hg while hens under the same experimental conditions only had average pressures of 94 mm Hg. Further studies on the sex difference in arterial pressure have shown that the male chicken generally has a blood pressure which is 15-25% higher than that of the female (95). Since a sex difference of this magnitude has not been demonstrated in arterial pressure of other animal species and since the sex difference in the chicken only becomes apparent upon maturity, it has been suggested that part of the sex difference might be due to variations in output and/or utilization of sex hormones between male and female chickens.…”

“…Age-For both sexes in the chicken, arterial pressures tend to increase with age after maturity (87,95,103). In a follow-up of day-old chicks (103), it has been shown that under the age of 8 weeks, there are no consistent sex differences in pressure.…”