The inhibitory effect of ACTH 1–10 on extinction of a conditioned avoidance response: Its independence of thyroid function

Abstract

The effect of the ACTH analogue ACTH 1–10 was studied on the rate of extinction of a pole jumping avoidance response in thyroidectomized rats with or without replacement therapy with 1-thyroxin. ACTH 1–10 appeared to delay the rate of extinction of the CAR in thyroidectomized rats in a similar way as in sham-operated animals. ACTH 1–10 was also active in thyroidectomized rats treated with thyroxin. The thyroxin treatment itself also caused a significant delay in the rate of extinction of the CAR. These results indicate that the inhibitory effect of ACTH analogues on the rate of extinction of the CAR is not mediated by the thyroid gland.