Developmental changes of aminopeptidase activity in the cortex of the cat brain.

Aminopeptidase activity has been proposed as a candidate regulator of the degradation of several neuroactive peptides. In this paper, possible changes in Lys-, Arg-, Asp- and Tyr-aminopeptidase activities in the cat brain neocortex (frontal, parietal, area 17 and areas 18 and 19 as a whole) were examined during two of the first stages of the critical developmental period (15 and 30 days postbirth). Aminopeptidase activities were studied by measuring the rate of hydrolysis of the artificial substrates Lys-, Arg-, Asp- and Tyr-2-naphthylamides (fluorimetrically detected in triplicate). Lys- and Arg-aminopeptidase activities do not show significant changes between the first the second stage in any of the cortical regions assayed. On the contrary, in all the cortical structures, activity with Tyr-2-naphthylamide shows significant increase with age. In contrast, the activity of Asp-aminopeptidase shows significant decreases on the 30th day (except in area 17). It is suggested that these activities play a part in the neurochemical changes that take place during cat brain maturation.