Abstract
Summary
This study was an attempt to induce hypertension in rats by the continuous psychosocial stimuli caused by aggregation. Wistar rats of both sexes were isolated from weaning to 4-5 mo of age. Tail cuff pressures were obtained every other week during the last 2 mo of isolation and up to 8 weeks of aggregation. Two types of physical conditions were used for aggregation: (1) 6 interconnecting cages in a wheel-like arrangement around a central eating and drinking area; (2) a single cage. Two wheels were used each with 24 rats, 12 males and 12 females and 10 single cages, each with 2 or 4 rats of the same sex. Other rats of both sexes remained isolated as controls. Approximately one-third of all aggregated rats of both sexes showed a 15 mm Hg or more average increase of systolic pressure during aggregation; other aggregated rats showed less average pressure rise. Rats in single cages did not fight nor did wheel aggregated females; nevertheless, arterial pressure increased among these rats. Among wheel aggregated males that developed hypertension, those classified as dominant types, by the least number of tail bites, had the largest pressure increases. The frequency of pressure increase was the same in dominant and nondominant wheel males.
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