Vasoactive intestinal polypeptide in sacral primary sensory pathways in the cat

Abstract

Unmyelinated sensory axons in the sacral spinal cord may play a role in bladder reflexes under certain pathological conditions. Previous data suggested vasoactive intestinal polypeptide (VIP) might be contained exclusively in sensory C‐fibers, some of which innervate the bladder. This study was undertaken to describe the morphology of these VIP fibers in the sacral cord of the cat. VIP immunoreactivity was confined to unmyelinated axons observed at several levels of the sensory pathway including the dorsal root ganglia, dorsal roots, Lissauer's tract, and the lateral collateral pathway. A combination of light and electron microscopic observations showed VIP‐immunoreactive fibers with labeled varicosities and synaptic terminals in laminae I, IIo, V, VII, and X. VIP‐immunolabeled varicosities had a mean diameter of 1.6 μm (range = 0.11–7.4 μm, S.D. = 1.01, n = 311) with a small percentage (8%) being relatively large (3–7.4 μm). VIP varicosities contained a mixture of small clear vesicles (CLV) and large dense core vesicles (LDV). Although most varicosities contained a moderate number of LDVs (14.86 LDVs/μm2), some varicosities contained a large number of LDVs, whereas others contained very few. Varicosities that possessed synaptic specializations were classed as terminals and were divided into three morphological classes. Two of these resembled Gray's Type I terminal, whereas a third was similar to the Gray's Type II terminal. There was no consistent relationship between vesicle content of the terminal and the type of synaptic contact it possessed. This study shows that in the sacral spinal cord of the cat, VIP terminals originate only from C‐fibers, terminate primarily in laminae I and V, and exhibit a variety of morphologies consistent with heterogeneous origins and functions of the lower urinary tract. J. Comp. Neurol. 407:381–394, 1999. © 1999 Wiley‐Liss, Inc.

Differential synaptic inputs to the cell body and proximal dendrites of preganglionic parasympathetic neurons in the rat conus medullaris

“…Immunohistochemical studies of the rat conus medullaris have also demonstrated in the IML the presence of several neuropeptides, including CGRP, substance P, vasoactive intestinal peptide (VIP), neuropeptide Y, galanin, and pituitary adenylate cyclase activating polypeptide (PACAP) (Gibson et al, 1986; Wang et al, 1998; Morgan et al, 1999; Vizzard, 2001; Zvarova et al, 2004, 2005). The association between neuropeptides and dense-cored vesicles in synaptic terminals of autonomic nuclei has also been supported by electron microscopy, as immunoreactivity for VIP has been detected ultrastructurally in synaptic terminals containing a mixture of clear and dense-cored vesicles in the sacral parasympathetic nucleus of cats (Morgan et al, 1999). Additional immunohistochemical studies combined with electron microscopy are needed, however, to determine which neuropeptidergic projections may exhibit a direct synaptic connection with the PPN somata and dendrites.…”

Expression of Phosphorylated cAMP Response Element Binding Protein (p-CREB) in Bladder Afferent Pathways in VIP−/− Mice with Cyclophosphamide (CYP)-Induced Cystitis

“…Greater basal activity in the primary bladder afferents in the DRG or in the target organ itself (i.e., urinary bladder) could result in increased pCREB expression in the absence of inflammation by increasing Ca ++ and/or cAMP in VIP −/− mice. Primary afferent cells in the DRG express VIP (Morgan et al, 1999;Hernandez et al, 2006) and VIP receptors (Yashpal et al, 1991;Braas et al, 2006). Thus, absence of VIP in the VIP −/− mice could produce a direct effect on primary afferent cells.…”

“…Neuropeptides are potential mediators or modulators of inflammation and are found in human micturition pathways (Chapple et al, 1992;Lasanen et al, 1992;Smet et al, 1997;Morgan et al, 1999;Uckert et al, 2002). Changes in the expression of neuropeptides have been observed with bladder overactivity (Chapple et al, 1992;Lasanen et al, 1992;Smet et al, 1997) and in animal models of bladder inflammation (Vizzard, 2000d(Vizzard, , 2001Zvarova and Vizzard, 2006).…”

Urinary Bladder Function and Somatic Sensitivity in Vasoactive Intestinal Polypeptide (VIP)−/− Mice

“…Neuropeptides are potential mediators or modulators of inflammation and are found in human micturition pathways (Chapple et al, 1992;Lasanen et al, 1992;Morgan et al, 1999). Changes in the expression of neuropeptides have been observed with bladder hyperreflexia (Chapple et al, 1992;Lasanen et al, 1992) and in animal models of bladder inflammation (Vizzard, 2000b(Vizzard, , 2001Zvarova and Vizzard, 2006).…”