Coexpression of neuropeptide Y and vasoactive intestinal polypeptide in pelvic plexus neurones innervating the uterus and cervix in the rat

The present study investigates the distribution and coexpression of neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) in neurones of the accessory ganglion (AG), hypogastric plexus (HP) and paracervical ganglion (PCG), which compose the pelvic plexus in the female rat. Nerve cell bodies immunoreactive for NPY and VIP represent 84% and 46% of the neurone population in the PCG, respectively, while immunoreactivity for each peptide is observed in about 90% of the AG and HP neurones. Adjacent sections immunostained for NPY and VIP, as well as the use of immunocytochemistry combined with in situ hybridization show that 92% of the VIP-containing neurones in the pelvic plexus also contain NPY. In addition, a retrograde tracing study performed in combination with immunocytochemistry demonstrates that pelvic plexus neurones project preferentially to the lower part of the uterus and to the cervix, and that about 95% of these projecting neurones contain VIP. Taken together, our findings indicate that in the female rat, neurones of the pelvic plexus projecting to the lower genital tract mainly coexpress VIP and NPY, and supply nerve fibres to the vascular and nonvascular smooth muscle in the uterocervical region. Since NPY and VIP exert distinct effects according to the target tissue, our results suggest that neurones coexpressing these peptides play important roles in the local regulation of the vascular bed and motor activity of the lower genital tract.