Adaptation of pregnant rhesus monkeys to short-term chair restraint.

Heart rate, blood pressure, temperature and plasma corticosteroids were measured in pregnant rhesus monkeys during 23 successive 2 hour chair restraint periods beginning in midgestation. Heart rate (15%), blood pressure (13%) and plasma cortisol (23%) declined from first to last sessions. Reduction in physiological indicators of stress was most marked during the first three sessions, but continued in some animals over the 8 week period. Pulse rate and blood pressure were elevated at the beginning of each session and dropped to base-line levels during the second hour. In contrast, plasma cortisol consistently rose during the 2 hour session. Blood sampling and palpation were conducted at weekly intervals during the adaptation series. Immediate physiological responses to these manipulations did not diminish with repetition, although behavioral adaptation was observed. The data suggests that objective measurements of adaptation to chair restraint are important in determining the appropriateness of this procedure. Chair restraint is a valuable alternative to chemical or manual restraint in obtaining sequential evaluations in pregnant monkeys.