Influence of new ACTH fragments on self-stimulation, avoidance, and grooming behavior in rabbits.

The effects of new cyclic analogs of ACTH fragments, EHFRWGKPVG-NH2 and KHFRWG-NH2, which have specific and nonspecific active centers in their structure, in the self-stimulation, avoidance, and grooming behavior of rabbits were investigated in this study. The intraventricular administration of EHFRWGKPVG-NH2 in doses of 0.1-2.5 micrograms increased the frequency of self-stimulation (SS), while in doses of 4-5 micrograms, it decreased the frequency of self-stimulation. The administration of KHFRWG-NH2 in doses of 0.1-5.o micrograms, induced a decrease in the frequency of SS by 25-30% in the first 15 min following the injections; this indicator returned to the baseline level thereafter, and decreased again. SS was more intense after 24-48 h, 5-8% higher than the baseline level, and remained practically unchanged over the course of a two-hour experiment. The administration of the EHFRWGKPVG-NH2 fragment in doses of 0.5-2.0 micrograms increased the latent period of the avoidance reaction, decreased the time of the anxiety state, and increased the time of the comfort state. In addition to these changes, both ACTH fragments induced intense grooming, increased the duration of grooming by 200-400% as compared with the control animals which were administered physiological solution.