Single neurones of the basal forebrain and laterodorsal tegmental nucleus project by collateral axons to the olfactory bulb and the mediodorsal nucleus in the rat.

The branching pattern of axons arising from cells in the basal forebrain and laterodorsal tegmental nucleus of the pontine grey, was examined using the double retrograde transport of rhodamine- and coumarin-labelled latex microspheres injected into the olfactory bulb and the mediodorsal thalamic nucleus. About 30-50% of basal forebrain neurones were double-labelled, and approximately 30-40% of laterodorsal tegmental neurones were double-labelled ipsilateral to the injections. No contralateral single or double label was observed in the basal forebrain, but approximately 30% of the contralateral laterodorsal tegmental projection was also double-labelled.