Localization of acetylcholinesterase-positive neurons projecting to the mouse main olfactory bulb.

In this study a technique for staining brain tissue for both acetylcholinesterase (AChE) and axonally transported horseradish peroxidase conjugated to wheat germ agglutinin (HRP-WGA) has been used to identify and quantitate the AChE-synthesizing neurons that project to the main olfactory bulb (MOB) of the mouse. The primary sites of double stained neurons included the nucleus of the horizontal limb of the diagonal band (including the nucleus basalis and the magnocellular preoptic nucleus), locus coeruleus and the lateral hypothalamic area. The AChE activity in the neurons of the locus coeruleus and lateral hypothalamic area is suggested to be related to possible cholinoceptive function or some other role, but not to cholinergic projections to the MOB. Therefore, the cholinergic projection to the mouse MOB is suggested to originate in the nucleus of the horizontal limb of the diagonal band, an area that, for the purposes of this study, includes the mouse equivalent of the nucleus basalis of Meynert and what has previously been known as the magnocellular preoptic nucleus.