Studies of the neuronal elements of the guinea pig anterior major pelvic ganglion

Abstract

The anterior major pelvic ganglion (AMPG) of the male guinea pig supplies the greater proportion of autonomic nerve fibres to the pelvic viscera and vasculature. Apart from a brief study (Schultzberg et al., 1983) the AMPG has not been extensively characterised in terms of the relationships between neuropeptides and classical neurotransmitters in the post-ganglionicand pre-ganglionic (including intraganglionic) components. The present study goes some way to rectifying this. Classical neurotransmitter associated enzymes (TH, DβH and AChE) were localised to groups of neuronal perikarya (producing regionalisation) and neuronal projections by indirect immunofluorescence and a histochemical method. Neuropeptides including NPY, VIP, ANF, SOM, MET, LEU and SP were localised to the neuronal elements of the AMPG by an indirect immunofluorescence method. The presence of multiple neuronal markers in neuronal perikarya established certain patterns of coexistence in the AMPG. Specific classes of neuronal perikarya could be related to immunoreactive (or histochemically reactive) groups of neuronal projections. Retrograde transport of fast blue dye injected into pelvic viscera, ductus deferens, seminal vesicle, urinary bladder(corpus/fundus), prostate and rectum, indicated that the AMPG innervate all the aforementioned viscera except for the urinary bladder (corpus/fundus). In fact, innervation of bilateral structures was from bilateral AMPG. Immunohistochemical analysis of dye laden neuronal perikarya demonstrated the `chemical coding' of groups of viscera-specific neurons. The selective or combined transection of the hypogastric and pelvic nerves allowed any segregation of neuropeptidergic neuronal projections to these inputs to be detected. SP- and LEU-immunoreactive neuronal projections are associated with both the hypogastric and pelvic nerves, while MET-immunoreactive neuronal projections appear to reach the AMPG via the hypogastric nerve. Hypogastric nerve transection produced the emergence of a few SP-immunoreative neuronal perikarya. AMPG maintained in vitro demonstrated that a far higher proportion of neuronal perikarya could exhibit SP-immunoreactivity; a property that could be down regulated by supplementing culture medium with different factors e.g. classical neurotransmitters or specific visceral factors.</p