Neonatal exposure to a high level of ACTH4-10 impairs adult learning performance

Male offspring of Sprague-Dawley dams were injected with 25 micrograms of ACTH4-10 or the vehicle on days 2 through 7 postpartum. Peptide treated animals exhibited a marked motor response to the peptide injection. Adrenal weights of these animals were consistently heavier than littermate controls in both the developing and adult animals. ACTH4-10 treated neonates exhibited significantly poorer learning performance in the shuttle box and were slower to acquire the reversal learning problem of a visual discrimination task under light shock levels. In addition, these animals also exhibited an exaggerated startle response and a stronger thigmotaxis response in the open field than controls. These results indicate that exposing the developing nervous system to relatively high levels of ACTH4-10 can produce marked long-term effects on behavior.