High affinity binding of an enkephalin analog in the cerebral ganglion of the insect Leucophaea maderae (Blattaria).

Specific high affinity binding sites for a synthetic enkephalin analog, DALA (D-Ala2-Met-enkephalinamide) were demonstrated in the cerebral ganglia of adults and nymphs of the insect Leucophaea. In both sexes binding was monophasic and saturable with respect to the concentration of the radioligand used. The same amount of brain tissue from adult females had 30% more binding sites for DALA than that from adult males. By contrast, no sex-related difference in binding-site density per mg protein was observed in the brains from immature (nymphal) specimens. The results strongly suggest the presence, in this invertebrate, of opiate receptors that appear to be confined to certain areas of the nervous tissue.