Regulation Of Smooth Muscle Activity Research Articles

Identification of C-Kit-Positive Interstitial Cells in the Dog Lower Urinary Tract and Relationship with Smooth Muscle and Nerves. Hypotheses for a Likely Pacemaker Role.

The aim of this work was to give an evidence of the likely presence of interstitial cells in the canine lower urinary tract and to study their possible interactions with the musculature and the intramural innervation. Cryosections of normal canine bladder and urethra were immunofluorescently labelled with c-kit, a transmembrane, tyrosine kinase growth factor receptor, known to be expressed on the interstitial cells of Cajal (ICCs) of the gut. The relationship with antiactin positive smooth muscle cells and PGP9.5-positive intramural innervation was also investigated by confocal microscopy. Anti-c-kit labelling demonstrated a network of elongated and branched c-kit positive cells, which were located in interstitial spaces, oriented in parallel to the smooth muscle bundles that form the bladder muscular layer, irrespective of dog sex. Cells with a similar localization were also PAS- and NADPH-diaphorase-positive. A contact between c-kit immunofluorescent cells and intramural innervation was demonstrated, too. The roles of interstitial cells might include regulation of smooth muscle activity of the bladder detrusor, integrating neuronal signals during urine storage and voiding.

Progesterone decreases the relaxing effect of the β3-adrenergic receptor agonist BRL 37344 in the pregnant rat myometrium

Although the published results regarding the function of the beta(3)-adrenergic receptors (beta(3)-ARs) in the regulation of smooth muscle activity are very promising, the question of the mechanism of beta(3)-ARs' action in the pregnant myometrium cannot be fully answered by human investigations. To assess whether it possesses an essential role in the regulation of uterine contractility in pregnant rats, as in humans, we performed functional, western blotting and molecular biology experiments on the late-pregnant rat myometrium. The influence of progesterone on the function of the beta(3)-ARs was also investigated. We demonstrated the presence and the functional activity of the beta(3)-ARs in the late-pregnant rat myometrium. The maximum dose-dependent uterus-relaxing effect of the selective beta(3)-agonist BRL 37344 was recorded at the end of pregnancy in rats, similarly as in humans. The extent of its relaxing action was regarded as moderate. The expression of beta(3)-AR protein and mRNA remained unchanged during the investigated period. The administration of progesterone had no effect on the beta(3)-AR mRNA and protein expression or the maximum relaxation effect of BRL 37344, but shifted the dose-response curve to the right and decreased the synthesis of the second messenger, cAMP. It can be concluded that the beta(3)-ARs play an additional role in the regulation of the contractile activity of the pregnant rat uterus. The inhibitory effect of progesterone on the functional activity of the beta(3)-ARs may have important consequences in the case of human application if this effect is also demonstrated in pregnant human myometrial tissue.

P2X 2 receptor expression by interstitial cells of Cajal in vas deferens implicated in semen emission

Male reproduction is dependent upon seminal emission mediated by vas deferens contraction. This drives spermatic fluid to the prostatic urethra during ejaculation. We localize interstitial cells of Cajal (ICC), which express P2X 2 receptor, subunits of ATP-gated ion channels, to rat, mouse and guinea-pig vas deferens submucosa. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of rat vas deferens resolved two functional splice variant transcripts of the P2X 2 receptor subunit. The P2X 2 receptor mRNA was localized principally within the lamina propria (submucosal) region of the rat vas deferens using in situ hybridization (ISH) and in situ RT-PCR-ISH. Immunohistochemistry using rat, mouse and guinea-pig vas deferens tissues confirmed expression of P2X 2 receptor protein within the lamina propria, particularly within a dense column of small spindle-shaped cells adjacent to the columnar epithelial cells which line the lumen. This immunoreactivity was co-localized with neurone-specific enolase (NSE) and c-Kit protein expression, gene markers for ICC. Mucosal mast cells were distinguished from ICC by toluidine blue staining. Choline acetyltransferase immunoreactivity, a marker for post-ganglionic parasympathetic innervation, occurred on the lateral margin of the lamina propria and extended into the inner longitudinal muscle layer. P2X 1 receptor immunolabelling was associated with sympathetic innervation of the smooth muscle in the outer longitudinal and circular muscle layers, but not the inner longitudinal layer. The physiological significance of the vas deferens ICC which express P2X 2 receptors remains to be established. Possible roles include regulation of smooth muscle activity or mucosal secretion utilizing local ATP signaling, both of which would affect semen transport.

Neuropeptides and the regulation of smooth muscle activity in echinoderms: Where's the catch?

Neuropeptides and the regulation of smooth muscle activity in echinoderms: Where's the catch?

Galanin-like immunoreactive nerve elements in the small intestine of the rat. An electron microscopic immunocytochemical study

Nerve cell bodies and fibres showing galanin-like immunoreactivity have been demonstrated in rat small intestine using immunocytochemistry. Immunoreactive cell bodies were observed in both the myenteric and the submucous plexuses. Immunoreactive nerve fibres were observed in all layers of the small intestine, especially in both plexuses and in the inner circular muscle layer. The immunoreactive nerve processes were found in close association (sometimes separated by less than 40 nm) with smooth muscle cells. These terminals contained both agranular vesicles (30–40 nm) and large granular vesicles (80–120 nm). Immunoreactive nerve fibres were sometimes seen in perivascular plexuses. It is concluded that, in rat small intestine, neurones expressing galanin-like immunoreactivity project to several different sites and may participate in a number of mechanisms, including the regulation of smooth muscle activity, mucosal cell secretion and blood flow; galanin may also be involved in interneuronal activity.

Ultrastructural identification of vasoactive intestinal polypeptide and neuropeptide Y-containing nerve fibres in the vas deferens of the guinea-pig

Vasoactive intestinal polypeptide (VIP)-like and neuropeptide Y (NPY)-like immunoreactive nerve fibres were identified by electron microscopic immunohistochemistry in the guinea-pig vas deferens. Labelled nerve fibres were observed in all layers of the wall. However, the NPY-like immunoreactive nerve fibres were most numerous in the muscle layer, and only a few labelled nerve processes were found in the tunica mucosa. In contrast, many of the VIP-like immunoreactive nerve fibres were found in close relation to the blood vessels, especially in the tunica mucosa. In the muscle layer, most immunoreactive nerve fibres were found in close relation to the smooth muscle cells; in these situations the separation between axon and muscle cell membranes was nearly always less than 100 nm, and in many cases as little as 20 nm. The ratio of large to small vesicles in the VIP-like immunopositive axons was 1 :3.1, while in the NPY-like immunoreactive nerve terminals the ratio was 1: 6.2. These ultrastructural observations confirm that VIP- and NPY-like immunoreactive nerve fibres exist in vas deferens and provide a morphological basis for the possibility that these fibres may participate in the regulation of smooth muscle activity and may influence blood flow in the vas deferens.

Electron microscopic study of neuropeptide Y-containing nerve elements of the guinea pig small intestine

Neuropeptide Y-containing nerve cell bodies and processes were identified by electron microscopic immunocytochemistry in the guinea pig small intestine. Labeled nerve processes were numerous in the myenteric plexus. However, a few immunoreactive nerve fibers were found in all layers of the small intestine. Some of the immunoreactive nerve processes were found in close apposition to the epithelial cells of the crypts of Lieberkühn and to endothelial and smooth muscle cells. The neuropeptide Y-containing nerve cell bodies were preferentially located in the submucous ganglia. In the myenteric plexus many synaptic connections were observed between the neuropeptide Y-immunoreactive nerve fibers and unlabeled nerve cell bodies and other nerve fibers. These findings provide a morphologic basis for the possibility that neuropeptide Y may act as a transmitter and exert postsynaptic effects on intrinsic neurons, in addition to participating in the regulation of smooth muscle activity and epithelial cell functions.

Responsiveness of rat vas deferens and stomach smooth muscles after treatment with indomethacin.

The contractile responses of rat vas deferens and longitudinal stomach fundus strips to stimulants and relaxants were studied after treatment with indomethacin (Ind) injected i.p. at doses of 15 mg/kg for 24 hr and 25 mg/kg for 48 hr. The treatment with Ind reduced the amount of both spontaneously and electrically-evoked release of a prostaglandin (PG)-like substance from the isolated n. hypogastricus-vas deferens preparations. A considerable decrease of the responsiveness to exogeneous noradrenaline occurred in vas deferens isolated from Ind-pretreated rats. The EC50 values of noradrenaline increased as compared to the control value. The contractile responses of the isolated longitudinal stomach fundus strips to acetylcholine, serotonin, PGE2, PGF2 and arachidonic acid were reduced while the relaxant action of noradrenaline and papaverine was potentiated after Ind treatment. It is assumed that endogeneous PGs participate in the regulation of smooth muscle activity through potentiation of the postjunctional excitatory action of noradrenaline in vas deferens and through interaction with the transmembrane ion transport in stomach fundus smooth muscles.