Small intensely fluorescent cells of the rat paracervical ganglion synthesize adrenaline, receive afferent innervation from postganglionic cholinergic neurones, and contain muscarinic receptors

In the paracervical ganglion (PCG) of the rat, double-labelling immunofluor escence for catecholamine-synthesizing enzymes and HPLC measurement of cate cholamine contents were first performed to evaluate whether intraganglionic small intensely fluorescent (SIF) cells are capable of synthesizing adrena line. Immunolabelling for tyrosine hydroxylase (TH), dopamine beta-hydroxyl ase and phenylethanolamine-N-methyl transferase (PNMT) occurred in all SIF cells of the PCG, thus demonstrating the presence of all the enzymes requir ed for adrenaline biosynthesis. Adrenaline levels were undetectable in the PCG but to test the hypothesis that PNMT is active in SIF cells, catecholam ines were measured in ganglia of rats pretreated with pargyline, an inhibit or of the monoamine oxidase, the major enzyme involved in the catecholamine degradation. Pargyline treatment increased adrenaline levels in the PCG, t hus demonstrating that SIF cells are capable of adrenaline synthesis. The u ndetectable levels of adrenaline in the PCG of untreated rats suggested a s low rate of biosynthesis of adrenaline in the ganglion. Furthermore, the us e of double-labelling showed that SIF cells of the PCG were stained for mus carinic receptors and were approached by varicose ChAT-immunoreactive nerve fibres. Nerve fibres immunoreactive for ChAT were also observed associated with nerve cell bodies of ganglion neurones. Following deafferentation of the PCG, the ChAT-immunoreactive nerve fibres surrounding nerve cell bodies totally disappeared indicating their preganglionic origin, while those ass ociated with SIF cells did not degenerate, which demonstrate that they deri ved from intraganglionic cholinergic neurones. Taken together, the results show that adrenaline may be a transmitter for SIF cells in the PCG and sugg est that cholinergic neurones of the parasympathetic division of the PCG ca n modulate the SIF cell activity through the activation of muscarinic recep tors. (C) 1999 Elsevier Science B.V. All rights reserved.