Low expression of FGF1 (fibroblast growth factor-1) in rat parasympathetic preganglionic neurons

Fibroblast growth factor-1 (FGF1), a member of the FGF family of growth factors, is localized in cholinergic neurons where it has trophic activity. We recently reported that cholinergic neurons in the dorsal motor nucleus of the vagus (DMNV) contain little FGF1, raising the possibility that FGF1 is not localized to parasympathetic preganglionic cholinergic neurons. To clarify this issue, we investigated the co-localization of FGF1 with cholinergic neuron markers in the Edinger-Westphal nucleus (EWN), salivatory nucleus, DMNV, and sacral parasympathetic nucleus by double immunofluorescence using antibodies to FGF1 and choline acetyltransferase (ChAT). The neurons in the EWN were devoid of FGF1. In the salivatory nucleus, 13% of ChAT-positive neurons were also positive for FGF1. In the DMNV, only 8% of ChAT-positive neurons contained FGF1, and in the sacral parasympathetic nucleus, 18% of ChAT-positive neurons were FGF1-positive. We also confirmed that a large number of ChAT-positive motor neurons in the oculomotor nucleus, facial nucleus, hypoglossal nucleus, and spinal motor neurons contained FGF1. The results confirmed that parasympathetic preganglionic neurons are largely devoid of FGF1, which is a unique feature among cholinergic neurons.