Development of Cardiovascular Responses in the Kitten

Abstract

In anaesthetized kittens the mean arterial pressure and the pulse pressure double during the first 6 weeks of life; the heart rates recorded were the same as in the adult cat and did not change during this period. The vasomotor sympathetic system was active within 4 days of birth: there was both tonic activity, as demonstrated by a rise in arterial pressure after carotid occlusion, and a rise in pressure during asphyxia; the carotid sinus-cardiac centre mechanism responded to a rise in arterial pressure at birth. All these responses increased with age but had not reached adult activity by the 6th week of life. The carotid sinus-cardiac centre mechanism did not respond to a fall in blood pressure until 4 weeks of age. The infant heart was apparently more sensitive to the direct action of acetylcholine and the peripheral blood vessels relatively less sensitive than in the adult.THE responses both to asphyxia and to the intravenous administration of drugs have been used to examine the activity of the cardiovascular reflexes shortly after birth. The neonatal period has been studied in the kitten and puppy [Clark, 1934], the pig [Adams, Hirvonen, Lind and Peltonen, 1958] and the human infant [James and Rowe, 1957;Adams, Lind and Rauramo, 1958]: observations have also been made in the growing rabbit [Bauer, 1938;Dawes, Handler and Mott, 1957]. The present paper gives an account of a similar investigation into some of the cardiovascular responses of kittens during the first 6 weeks of life when the central arterial pressure is found to increase from 50/40 mm. Hg, at birth, to 120/90 mm. Hg at 6 weeks of age; the cardiovascular responses to positive intrathoracic pressure have been studied; graded doses of the autonomic transmitter drugs have also been used in an attempt to alter the balance between the direct action on the myocardium and peripheral vessels and the regulatory mechanisms involved. The responses are compared with similar observations made on fully grown animals under comparable experimental conditions and discussed in relation to the change in blood pressure during growth. METHODSNineteen kittens, 96-305 g. in weight, aged from 1 to 46 days and eight adult cats, 2-7-4-5 kg. in weight, were used in the experiments. A few observations were also made on five puppies aged 5-110 days, weighing 475 g.-3-3 kg.Aneesthesia was induced with sodium pentobarbitone, 20-30 mg./kg. injected into the saphenous vein exposed after the subcutaneous injection of procaine. The arterial pressure was measured in a carotid or a femoral artery cannulated with a saline-filled polythene tube connected to a capacitance-or inductance-type manometer; recordings were taken with a Sanborn or a New Electronic Products recorder

The effect of haemorrhage on haemoglobin concentration, blood volume and arterial pressure in kittens and cats

“…Windle, Sweet & Whitehead (1940) Cardiovascular system. The arterial pressures recorded in this paper are similar to those reported by Hutchinson, Percival & Young (1962) except that their mean values in very young kittens were slightly below rather than above 50 mm Hg. However, the fact that they never administered less than 20 mg/kg pentobarbitone may be relevant here.…”

Age-related cardiovascular effects of catecholamines in anesthetized piglets.

“…Catecholamine actions on blood pressure and heart rate have been examined in groups of fetal or neonatal mammals (Adams et al, 1958;Friedman, 1972;LeBlanc and Mount, 1968;Rudolph and Heymann, 1974), and some studies of age-dependent changes have been reported (Alexander et al, 1972;Boatman and Brody, 1967;Boatman et al, 1965;Gauthier et al, 1975;Hutchinson et al, 1962;Woods et al, 1977). However, few investigators have evaluated peripheral blood flow responses to catecholamines (Alexander et al, 1972;Boatman et al, 1965;Rudolph and Heyman, 1974).…”

“…However, few investigators have evaluated peripheral blood flow responses to catecholamines (Alexander et al, 1972;Boatman et al, 1965;Rudolph and Heyman, 1974). The cardiovascular responses in lambs (Alexander et al, 1972;Rudolph and Heyman, 1974;Woods et al, 1977), young dogs (Boatman and Brody, 1967;Boatman et al, 1965;Gauthier et al, 1975;Geis et al, 1975), and kittens (Hutchinson et al, 1962) indicate that there are differences in relative maturity of different mammals at birth. Our findings in piglets include: (1) age-related differences in catecholamine dose found to alter cardiovascular function, (2) age-related differences in magnitude of cardiovascular responses to a selected moderate dose of catecholamines, and (3) age-related differences in direction of heart rate and blood pressure changes after injections of NE and E, respectively.…”

Cellular mechanisms of impaired adrenergic responsiveness in neonatal dogs.

“…Despite a thorough examination of the neonatal cardiac responsiveness to adrenergic stimulation (1, 2), the developmental modulation of this autonomic control is still incompletely understood. Early investigators have found both neonatal subsensitivity (3)(4)(5) and supersensitivity (6)(7)(8) of peripheral vessels to vasoactive drugs in the newborn. Fewer studies have examined the responsiveness of the neonatal heart to catecholamines.…”