Identification of central cholinergic neurons containing both choline acetyltransferase and acetylcholinesterase and of central neurons containing only acetylcholinesterase.

Neurons in the rat central nervous system (CNS) were examined for their content of both the acetylcholine-synthesizing enzyme, choline acetyltransferase (ChAT; acetyl-CoA, choline O-acetyl-transferase, EC 2.3.16), and the transmitter-degrading enzyme, acetylcholinesterase (AChE). ChAT was localized immunohistochemically and AChE was localized histochemically in normal, colchicine-treated, or diisopropylfluorophosphate (DFP)-treated rats, either in neighboring sections by standard procedures or simultaneously in the same sections by immunofluorescence for ChAT, followed by photography, followed by histochemistry for AChE, followed by brightfield rephotography of the same neurons. This combination of fluorescence and brightfield procedures allows both to be carried out at maximum intensity without fear of interference and enables the unambiguous visualization of all neurons that might be expected with either procedure. Based on previous examination of singly stained neighboring sections, five CNS areas were examined in detail in DFP-treated rats using the simultaneous procedure for localizing both ChAT and AChE in the same neurons in the same sections. Several hundred neurons were thus examined in each area. These areas were the caudate putamen, nucleus basalis of Meynert, medial septum, nucleus of the diagonal band of Broca (vertical and horizontal limbs), and zona incerta. In the caudate putamen and nucleus basalis magnocellularis of Meynert, all ChAT-positive neurons contained AChE and vice versa. In the medial septum and nucleus of the diagonal band of Broca, all ChAT-positive neurons contained AChE, but these neurons containing both ChAT and AChE were intermingled with neurons positive only for AChE.(ABSTRACT TRUNCATED AT 250 WORDS)