Influence of enkephalins on the ACTH-induced hormonal imprinting in tetrahymena

Both adrenocorticotrop hormone (ACTH) and the synthetic enkephalins investigated evoked imprinting in Tetrahymena and led to increased hormone binding at further contact with ACTH. Neither molecule evoked, however, imprinting for the enkephalins. The pentapeptide enkephalin containing also proline had the most pronounced imprinting effect and, when given together with ACTH, it increased the imprintatory effect of ACTH considerably. In all the situations investigated the enkephalin tetrapeptide inhibited the positive effect of the enkephalin pentapeptide, whereas it did not influence the imprintatory effect of ACTH. Similarities can be found between the pharmacological and imprinting effects of enkephalin in mammals, and the effects seen in the present investigations.