Comparative microdistribution of the activity of catecholamine-synthesizing enzymes in horizontal sections of the rat...

The activities of the three major catecholamine-synthesizing enzymes were determined in brain tissue pellets dissected from 500-micrometers thick horizontal sections of rat lower brainstem. The rostrocaudal distributions of the three enzymatic activities were generally not parallel, suggesting differences in the respective localization of the noradrenergic and adrenergic neurons. The difference was most important in the A2-C2 region where the maximal activity of phenylethanolamine-N-methyltransferase (EC 2.1.1.28) was located 1.5 mm more rostrally than the maximal activities of the tyrosine hydroxylase (EC 1.14.16.2) and dopamine beta-hydroxylase (EC1.14.17.1). This result indicates that a more specific dissection of the adrenergic and noradrenergic neurons could be performed in the A2-C2 area of the rat brainstem.