STRESS REACTION TO INTENSE SOUND EXPOSURE UNDER DIFFERENT AROUSAL LEVELS IN GUINEA-PIGS

The general impact of high intensity sound exposure on 25 guinea pigs was investigated at three different levels of arousal: 10 during gener al anaesthesia, 10 during partial arousal, and 5 during complete arous al. Parameters recorded before and during noise exposure were mean art erial blood pressure, pulse rate, and plasma norepinephrine levels. Th e anaesthetized group showed no increase in the three parameters durin g sound exposure. Under partial arousal, pulse rate and norepinephrine level increased significantly: pulse rate from 224.5 beats/min before exposure to 278.6 beats/min during exposure, and norepinephrine level from 558 pg/ml before sound exposure to 1276 pg/ml during exposure. A t the time of the complete arousal state norepinephrine and pulse rate s increased significantly during noise exposure, while blood pressure showed no additional increase as a result of sound exposure.