INCREASED ACOUSTIC SENSITIVITY IN DOGS FOLLOWING ROENTGEN-RADIATION OF THE HYPOPHYSIS

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Abstract
The previously reported transient gain in acoustic sensitivity following x-radiation of the head is confirmed for 3 frequencies (125, 1000 and 8000 cycles). 2 objections to the validity of this effect are explored and answered: a) It can not be ascribed to increased random responsiveness of the conditioned limb, since spontaneous activity of the test-limb does not increase after Roent-genization, and even when, for other causes, spontaneous activity of the test-limb does increase, the animal''s acoustic thresholds, as measured by our methods, are not affected; b) The dosage required to produce the hearing-effect is more than ample to penetrate the entire cranial content of a dog. Both magnitude and duration of the effect remain constant throughout the range, 75-675 r-units; but its latency decreases as X-ray dosage increases. The effect is slightly less at low frequencies (125[image]) than at medial and high levels (1000 and 8000[image]). 2 normal animals, when radiated on areas other than the head, showed no trace of the effect; 2 hypophysectomized dogs, when radiated, revealed no change in acoustic threshold; hence the effect issues from the pituitary gland. About 40 days after hypophysectomy, without an exposure to x-rays, the threshold of these 2 dogs declined and remained about 5 db below its previous level. This fact, combined with the other evidence, implies a 2-fold acoustic change: a) the true "x-ray effect," appearing within a few days, due to a mild and transient depression of sugar throughout bodily fluids, including peri- and endo-lymph; and b) the "hypophysectomy effect" which first, like x-rays, produces a moderate hearing-gain and later, after 40 days, a 2d gain, symptomizing the continued depression of sugar to a more severe and chronic level. A diabetic subject, and also a normal dog showed increased acuity when blood-sugar was lowered with insulin and reduced sensitivity when blood-sugar was raised. The sugar-level of an X-rayed animal was subnorml during the period when its acoustic threshold was subnormal. The mechanism of the above effects is briefly set forth.

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