ARTERIAL PRESSURE CORRECTION IN RATS WITH INHERITED HYPERTENSION BY MODIFICATION OF CATECHOLAMINE METABOLISM IN EARLY ONTOGENY E. V. Naumenko, L. N. Maslova, A. L. Markel', and N. I. Gordienko UDC 616.12-008.331.I-055.5/.7-084:616. 452-008.6-053.31-02:615.31-547. 583.5 KEY WORDS: heredity; arterial hypertension; catecholamines; ontogeny; correction. It has been shown on SHR rats with inherited hypertension that changes in catecholamine mechanisms take place in the relatively early period of individual development [i] and that persistent hypertension may be formed as early as the 8th-10th week of life [7, 12]. It is claimed that an essential role in the pathogenesis of the raised blood pressure (BP) of such animals may be played by weakening of the sympathicoinhibitory tone of central noradrenergic mechanisms [13]. Profound changes in the function of central noradrenergic structures have been found by the writers in rats of a different line, with inherited arterial hypertension (inherited stress-sensitive arterial hypertension, ISSAH), which is evidently one of the lead- ing causes of the lasting elevation of BP in these animals [3]. The writers showed previously that changes in catecholamine metabolism at certain periods of early ontogeny are accompanied by long-term modification of the noradrenergic system of the brain [14]. The aim of this investigation was to seek to obtain possible normalization of BP in rats with inherited hypertension by short-term intervention in catecholamine metabolism in early ontogeny. EXPERIMENTAL METHOD The investigation was conducted on rats with inherited hypertension (ISSAH line) belong- ing to the 16th, 17th, and 18th generations of breeding. This line was obtained by breeding Wistar rats on the basis of their BP level under conditions of emotional stress [2]. On the 7th-9th, 14th-16th, 21st-23rd, or 21st-25th days after birth the young rats were given daily intraperitoneal injections of an aqueous suspension of the dopamine precursor L-dopa (Reanal, Hungary) in a dose of i mg/10 g body weight. Intact animals or young rats receiving injec- tions of 0.i ml distilled water/lO g body weight served as the control. To inhibit noradren- alin synthesis, some rats were given an injection of a suspension of the dopamine-B-hydroxy- lase inhibitor SLA-59 (Serva, West Germany) in a dose of 0.15 mg/10 g body weight, made up in 0.5% Tween-80 (Ferak, West Germany) at the age of 21-25 days, 3 h before the injection of L- dopa. The control animals of this group received injections of 0.i ml Tween, followed by dis- tilled water, in a volume of 0.i ml/10g body weight, 3 h later. On the 30th day after birth the young rats (6-8 in a litter) were weaned. At the age of 40 days the young rats were sep- arated by sex and formed into randomized groups with eight animals in each group. Experi- ments were carried out on males aged 4-4.5 months, placed in individual cages i week before the experiment began. BP was measured with a sphygmomanometer in the tail at rest and after emotional stress, as described previously [2]. Emotional stress was induced by immobilizingthe rats in a con- straining wire cylinder for 30 min. The results were subjected to statistical analysis by Student's t test. EXPERIMENTAL RESULTS Daily injections of the dopamine precursor L-dopa into young rats aged 7-9 or 14-16 days, belonging to the 16th generation of breeding, were not accompanied by any change in BP of these Laboratory of the Genetic Bases of Neuroendocrine Regulation, Institute of Cytology and Genetics, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk. (Presented by Acad- emician of the Academy of Medical Sciences of the USSR A. V. Val'dman.) Translated from Byul- leten' Eksperimental'noi Biologii i Meditsiny, Vol. 104. No. i0. pp. 464-466, October, 1987. Original article submitted December ii, 1986. 0007-4888/87/0010-1427512.50 9 1988 Plenum Publishing Corporation 1427