Hypersensitivity of Spontaneously Hypertensive Rats (SHR) to Heat, Ether, and Immobilization*

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Abstract
The responses to immobilization, ether, and heat of spontaneously hypertensive rats (SHR) and normotensive Sprague-Dawley rats (S-D) were compared. Hyperglycemia reached a maximum within 5 min of exposure and was most intense in SHR. There were no differences in the pituitary content of GH or PRL between the SHR and S-D. Circulating GH levels were especially depleted in SHR 15 min post exposure, with rebound to high blood levels at 1 h. Circulating PRL levels were slightly higher in quiescent SHR vs. S-D but surged to much higher levels post exposure in SHR vs. S-D. Postexposure blood corticosterone and aldosterone levels rose to much higher levels in SHR vs. S-D. Although the blood glucose, GH, PRL, corticosterone, and aldosterone levels are similar in hypertensive SHR and normotensive S-D under quiescent conditions, SHR appear to be much more sensitive and respond more vigorously to heat, ether, and immobilization. It is suggested that abnormal activity of the hypothalamic-pituitary system may play a role in the pathogenesis of the genetically programmed hypertension of SHR.