Habituation by the immature fowl in response to repeated injections of corticotrophin

Abstract

Immature birds [chicken] treated for 7 d [day] with corticotropin (30 IU/kg, 1 injection per d) had significantly poorer growth rates and decreased adrenal cholesterol concentrations. Plasma glucose, corticosterone and cholesterol concentrations and adrenal weight were within the normal range 24 h after the last injection. The responses of birds pretreated as described above to a single injection of corticotropin (30 IU/kg) were determined. A similar degree of hyperglycemia had developed in both groups after 2 h, but thereafter the responses differed: the concentration of plasma glucose did not increase further in those pretreated with corticotropin and had begun to decrease at 6 h, whereas that of the birds pretreated with saline increased progressively. The concentrations of plasma corticosterone had increased similarly in the 2 groups to a peak at 2 h, but there was a significantly more rapid decrease in the birds pretreated with corticotropin. Both groups showed a transient hypercholesteremia, but the increase was significant only in the group that had previously received saline. There were decreases in the concentrations of adrenal cholesterol in both groups. The decrease, in absolute terms, was 2.4 .times. greater in the group receiving corticotropin for the 1st time; percentage changes were similar, however.