The effect of ACTH-analogues on motor behavior and visual evoked responses in rats

Averaged visual evoked responses (VER) in cortical area 17 were recorded one hour after the administration of 7-l-phe ACTH4-10 or 7-d-phe ACTH4-10 to artificially ventilated rats, paralysed with gallamine. In addition, the effects of these peptides on spontaneous motor behavior were analysed. The results show that the latencies of all VER components remain unchanged and the amplitudes of the primary VER were unaffected. Measured at a wide variety of light intensities, however, the amplitudes of the VER afterdischarge were significantly and very similarly diminished by both peptides, the effect of 7-l-phe ACTH4-10 being somewhat stronger than that of 7-d-phe ACTH4-10. These results support the notion, advanced by others, that these peptides have an effect on a CNS vigilance regulating system, yet do not explain the reported opposite effects on active avoidance behavior of the two related peptides. The effects appear specific since spontaneous motor behavior, as index of changes in generalised arousal, is unaffected by these two peptides.