DISTRIBUTION OF CHOLINE-ACETYLTRANSFERASE AND ACETYLCHOLINESTERASE INVOCAL CONTROL NUCLEI OF THE BUDGERIGAR (MELOPSITTACUS-UNDULATUS)

The present study used histochemical methods to map the distributions of choline acetyl transferase (ChAT) and acetylcholinesterase (AChE) i n the vocal control nuclei of a psittacine, the budgerigar (Melopsitta cus undulatus). The distributions of ChAT and AChE in budgerigars appe ared similar to that in oscine songbirds despite evidence that these s ystems have evolved independently. The magnicellular nucleus of the lo bus parolfactorius in budgerigars, like the area X in songbirds, conta ined many ChAT labeled somata, fibers, and varicosities and stained de nsely for AChE. In contrast, the robust nucleus of the archistriatum ( RA) and the supralaminar area of the frontal neostriatum in budgerigar s, like the RA and the magnicellular nucleus of the neostriatum (MAN) in songbirds, respectively, contained few or no ChAT labeled somata, f ibers, and varicosities and stained lightly for AChE. The central nucl eus of the lateral neostriatum in budgerigars, like the higher vocal c enter (HVC) in songbirds, contained no ChAT labeled somata, moderate d ensities of ChAT labeled fibers and varicosities, and moderate levels of AChE staining. Two nuclei, the oval nucleus of the hyperstriatum ve ntrale (HVo) and the oval nucleus of the anterior neostriatum (NAo), c ontained no ChAT labeled somata, dense ChAT labeled fibers and varicos ities, and moderate to high levels of AChE staining. The HVo and the N Ao have no counterparts in songbirds but may be important vocal contro l nuclei in the budgerigar. Cholinergic enzymes are also described in other regions which may be involved in budgerigar vocal behavior, incl uding the basal forebrain, the torus semicircularis, and the hypogloss al nuclei (nXII). (C) 1996 Wiley-Liss, Inc.