Effects of Insulin Shock on Behavior and Conditioned Reflex Action in the Well Trained Sheep.

Abstract

Insulin shock has radically, and perhaps permanently, altered the behavior of a sheep whose conditioned reflexes and general behavior have been studied for 7 years. During the year preceding the insulin experiment the conditioned motor reflex had gradually failed (Fig. 1-A) although the sheep remained quiet and alert during the 20-minute test period. The sheep was started on 10 units of insulin and the daily dose was increased by 10 to 15 units until coma and convulsions occurred. First signs of coma were observed at 160 units but dosage was carried to 280 units in an effort to secure typical shock phenomena. Convulsions were induced on 7 successive days. No discrepancies in the results as given below for a typical day were observed. Insulin is given to the fasting sheep at 9 A. M.; in 5 hours it is standing with head drooping, lips twitching, and must be carried into the testing laboratory. It is placed upon the observation platform with great difficulty. When in the testing frame the sheep is induced to stand but soon slowly sinks. After a few minutes it rises and stands for a few minutes, then sinks again. When standing, the head gradually droops, the eyelids close; then suddenly the head is raised and the eyes are opened. This sequence is repeated many times throughout the first part of the observation period. At this time the heart rate is normal or below normal (80-60); breathing is labored and noisy. The animal is now tested. It not only shows no conditioned motor (defensive) reflex but fails to respond to any outside stimulus. In an effort to show what is happening to the animal at all times, the conditioning test (sound of buzzer for 10 seconds followed by shock to the left foreleg) is repeated at the usual 5-minute intervals in the coma, the recovery period, and for some time after. After about an hour of fairly severe convulsions glucose is administered by mouth.