EFFECT OF ULTRASOUND ON THE NEONATAL RAT-BRAIN

Six-day-old rat neonates were exposed to 2.25 MHz continuous wave (CW) ultrasound for 5 min at an intensity of 2.5 W/cm2 (SATA). The temperatures on the head surface and in the mouth were measured. There was a higher average temperature elevation in the mouth (9-degrees-C) than on the head surface (7-degrees-C). Survival differs between control and exposed groups at 30 days after exposure. Ninety percent of the control group lived to 30 days, versus 59.7% for the exposed group. At differing times following exposure, the brains of the pups were removed and tested for enzymatic activities. Changes in acetylcholine esterase and in 2',3'-cyclic nucleotide phosphohydrolase activities were not statistically significantly different from controls. There were no significant differences in brain weight and total protein between control and exposed pups.