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PubMed1980

Pseudohypertension in sinoaortic-denervated rats.

1. Mean arterial pressure was determined continuously over a 24-h period by computerized data collection in eight control and nine sinoaortic-denervated rats housed in standard-sized metabolic cages. In addition, direct and indirect pressure measurements were made while the rats were resting in a Lucite restrainer. 2. Pressure measurements made during restraint indicated that the baroreceptor-denervated rats were hypertensive: mean aortic pressure averaged 145 +/- 3.4 mmHg (mean +/- SEM) in denervated rats vs 119 +/- 2.8 mmHg in control rats (P < 0.001), and tail-cuff pressure averaged 156 +/- 5.4 mmHg compared with 121 +/- 2.7 mmHg in the control group (P < 0.001). 3. In contrast, continuous pressure monitoring showed the sinoaortic-denervated rats were normotensive (mean arterial pressure averaged 119 +/- 4.7 mmHg vs 119 +/- 3.1 mmHg in control rats). 4. Apparently arterial pressure is elevated during restraint in sinoaortic-denervated rats and pressure measurements made under these conditions give a false indication of hypertension.

Animals↗
PubMed1982

Effect of acute unilateral renal denervation on intrarenal haemodynamics and urinary excretion in rats before and during hypervolaemia.

1. The possible involvement of renal nerves in the diuresis and natriuresis of blood volume expansion was studied in anaesthetized rats. Acute unilateral renal denervation caused increased excretion of fluid, sodium and potassium. 2. Renal blood and plasma flows were elevated without change in filtration rate. Intracortical blood flow distribution was not affected by the denervation. 3. Blood infusion caused diuresis, natriuresis and kaliuresis in both denervated and sham-denervated kidneys, associated with comparable initial increases in filtration and decreases in renal blood flow. No change in flow distribution was found, whether or not renal nerves were intact. 4. Although the magnitude of the excretory response to hypervolaemia was greater in denervated kidneys, the temporal pattern was identical with that of sham-operated kidneys. Our data thus do not show an effect of efferent renal nerve activity on volume natriuresis.

Animals↗
PubMed1997

Supersensitivity in rat micro-arteries after short-term denervation.

Contractile responses to phenylephrine and high-K+ were investigated in vitro in microvascular preparations from the rat medial plantar artery, a branch from the saphenous artery, obtained after short-term denervation in vivo. Two groups of animals were studied: (1) animals undergoing surgical resection of the saphenous nerve, and (2) animals undergoing surgical resection of both the sciatic and saphenous nerves. The animals were operated on one side only. Microvascular preparations (diameter about 325 microns) were obtained 10 days after surgery. Vessels from the non-operated side served as controls. Immunocytochemistry showed a decreased number of both neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) immunoreactive nerve fibres in vessels after resection of the saphenous nerve only. Resection of both the saphenous and the sciatic nerve caused a complete loss of immunoreactive nerve fibres. Mechanical measurements were performed using a wire myograph. In vessels subjected to resection of the saphenous nerve the sensitivity to phenylephrine was similar to controls. Vessels denervated by resection of both the saphenous and sciatic nerves showed significant increases in phenylephrine and potassium sensitivity. When depolarized in high-K+ solution the denervated vessels showed an increased sensitivity to extracellular Ca2+. The results show that complete short-term denervation of the rat medial plantar artery in vivo causes a pronounced supersensitivity in the vascular smooth muscle. The supersensitivity appears not to be restricted to the sympathetic alpha-receptors but also associated with changes in the cellular excitation-contraction coupling. Such altered reactivity of the vascular smooth muscle may contribute to vascular disturbances observed in vivo after nerve damage or surgical denervation.

Adrenergic alpha-Agonists↗
PubMed1998

Matrix metalloproteinases MMP-2 and MMP-9 in denervated muscle and injured nerve.

Nerve crush or axotomy results in a transient or longterm denervation accompanied by remodelling in nerve, muscle and neuromuscular junctions. These changes include an increased turnover of several extracellular matrix molecules and proliferation of Schwann cells in injured nerves. Given the role of matrix degrading metalloproteinases MMP-2 and MMP-9 (gelatinases-type IV collagenases) in extracellular matrix remodelling, we investigated their regulation and activation in denervated muscles and injured nerves in mice. For this, immunofluorescence using MMP-2 and MMP-9 antibodies was carried concomitantly with gelatin zymography and quantification of gelatinase activity using [3H]-gelatin substrate. Results show that in normal mouse muscles MMP-2 and MMP-9 are localized at the neuromuscular junctions, in Schwann cells and the perineurium of the intramuscular nerves. In denervated mouse muscles, MMP-2 immunolabelling persists at the neuromuscular junctions but decreases in the nerves whereas MMP-9 immunolabelling persists at the neuromuscular junctions but is enhanced in degenerated intramuscular nerves. Denervated muscles did not show any significant change of gelatinolytic activity or expression pattern, while injured nerves exhibited a transient increase of MMP-9 and activation of MMP-2. In conclusion, this study demonstrates that MMP-2 and MMP-9 are expressed at mouse neuromuscular junctions and that their localization and expression pattern appear not to be modified by denervation. Their modulation in injured nerves suggests they are involved in axonal degeneration and regeneration.

Animals↗
PubMed1999

Denervation of rabbit gastrocnemius and soleus muscles: effect on muscle-specific enolase.

We report here, for the first time, the expression of the muscle-specific isoform of the glycolytic enzyme, enolase (EC 4.2.1. 11) (beta enolase), in rabbit skeletal muscles. We have analysed the fast-twitch gastrocnemius and the slow-twitch soleus muscles during normal postnatal development and following denervation. We show that, in rabbit, as already described in rodents, beta enolase gene expression behaves as a good marker of the fast-twitch fibers. In soleus muscle, the beta enolase transcript level is 10-20% of that found in gastrocnemius. Denervation, performed at 8 postnatal days, induces an important drop of beta enolase transcript levels in both developing soleus and gastrocnemius muscles, with a 80% decrease observed 1 week after denervation in the operated muscles, as compared to the corresponding contralateral muscles. Thereafter, the beta enolase transcript level continues to decrease in the fast-twitch muscle, with the beta enolase subunit being detectable only in the atrophic fast-twitch fibers. In contrast, the beta transcript level tends to increase in the denervated slow-twitch muscle, reaching about 50% of that in contralateral soleus, at 7 weeks after surgery. The level of beta enolase transcripts still expressed after denervation seems to stabilize at the same low level in both types of inactive muscles. This suggests that the small fraction of beta enolase expression which is not controlled by the nerve, or by the contractile activity imposed by it, is independent of the muscle phenotype.

Animals↗
PubMed2000

Effects of renal denervation on the sodium excretory actions of leptin in hypertensive rats.

BACKGROUND: Previous studies from this laboratory have reported a marked attenuation of the renal responses to pharmacologic doses of synthetic murine leptin infused in the spontaneously hypertensive rat (SHR) model compared with normotensive Sprague-Dawley and lean Zucker rat models. METHODS: In the present study, the hemodynamic and renal excretory effects of an intravenous bolus administration of pharmacologic doses of synthetic murine leptin were examined in groups of anesthetized SHR with unilateral nephrectomy and renal denervation or sham-denervation of the remaining kidney. RESULTS: In the SHR with acute renal denervation (N = 8), an intravenous bolus of 1600 microg/kg of leptin produced a significant twofold to fourfold elevation in sodium excretion but did not increase natriuresis in the sham-denervated group (N = 6). Chronic renal denervation of one-week duration (N = 8) was associated with qualitatively and quantitatively similar increases of sodium excretion in response to leptin administration. Mean arterial pressure remained unchanged in all groups after the administration of leptin. CONCLUSIONS: Collectively, these results are interpreted to suggest that the blunted natriuretic and diuretic responses to leptin observed in the SHR with intact renal nerves may be partially explained by the antinatriuretic effect of an enhanced baseline efferent renal sympathetic activity and/or leptin's stimulation of the sympathetic nervous system.

Animals↗
PubMed2003

Ileal resection enhances jejunal absorptive adaptation for water and electrolytes to extrinsic denervation: implications for segmental small bowel transplantation.

BACKGROUND/PURPOSE: Segmental small bowel transplantation (SBT) may be an alternative to whole jejunoileal SBT. The aim of this study was to evaluate adaptability of extrinsically denervated jejunum after ileectomy. METHODS: Baseline absorption of an isomolar, nonnutrient electrolyte solution was measured in an 80-cm in situ jejunal segment. Control (CON) and extrinsically denervated dogs (EXT DEN) then underwent distal 50% enterectomy; EXT DEN dogs also underwent a complete extrinsic denervation of remnant jejunum. Absorption was remeasured 2 and 12 weeks later; jejunal biopsies at 12 weeks were compared with baseline. RESULTS: All dogs experienced weight loss and diarrhea, which resolved by 10 weeks in CON but persisted in EXT DEN dogs. Net absorptive fluxes of water, Na+, K+, and Cl-, however, remained unchanged in both groups 2 weeks and 12 weeks after denervation. Morphometric evaluation showed an increase in crypt depth in both groups at the 12-week time-point. CONCLUSIONS: Despite a clinical short bowel syndrome, more weight loss, and diarrhea in EXT DEN, there were no temporal differences in net absorptive fluxes of water and electrolytes within or between these 2 groups, and both developed increased crypt depth at 12 weeks. Extrinsic denervation does not blunt jejunal adaptive response to ileectomy.

Adaptation, Physiological↗
PubMed1999

Denervation of Pacinian corpuscles: electron microscopic observations in the rat following nerve transection.

Nerve transection using rat sciatic nerves was employed to observe morphologic changes in the periodic denervation of Pacinian corpuscles. During periods of from 1 to 20 weeks after surgery, a total of 15 corpuscles were obtained under the operating microscope and processed for morphologic analysis using light and electron microscopes. Based on the morphologic findings, normal corpuscles were composed of an axon terminal and inner and outer core cells. Following nerve transection, the axon terminal immediately disappeared at 1 week, but the original inner and outer core cells were preserved, with macrophage migration occurring in the outer core. After 8 weeks, the circular regularity of the inner and outer core lamellae was occasionally broken. The lamellae had wavy courses and there were many empty spaces in the inner core. Even at 20 weeks after denervation, there was interruption in the continuity of the outer core cells; the membranous structure of the outer core and the lamellar structure of the inner core were well-preserved; the outer and inner core cells were still present. Simultaneously, a small number of collagen fibrils were observed between the inner and outer core cells from the earliest postoperative stage. These fibrils increased in number in later stages. The results suggest that, immediately after destruction of axon terminals, macrophages migrate into the interlamellar spaces where they engulf the debris of the degenerated axon terminals. The degeneration of the corpuscles seems to be similar to that of denervated nerve axons; therefore, the inner core cells, which are continuous with the Schwann cells, maintain their original condition for at least 20 weeks after corpuscle denervation. The outer core cells, which are continuous with the perineurial nerve cells, are assumed to be the main cells producing the collagen fibrils in the denervated Pacinian corpuscles.

Animals↗
PubMed1999

Denervation of rabbit lacrimal gland increases levels of transferrin and unidentified tear proteins of 44 and 36 kDa.

PURPOSE: The main lacrimal gland secretes proteins and fluid that make up the aqueous component of the tears. Previous reports indicate that the parasympathetic innervation of the gland influences the secretion of protein from the lacrimal gland. We investigated the effect of lacrimal nerve transection on the levels of individual proteins and overall protein concentration in the tear fluid. METHODS: The main lacrimal gland was unilaterally denervated in adult rabbits at the site of nerve entry to the gland. The contralateral gland (sham-operated) had identical surgical manipulations, excluding nerve transection. Tears were collected daily from both eyes for up to 9 days, after which lacrimal glands were collected. SDS-PAGE, densitometric and image analysis, and Western blot were performed. RESULTS: Consistently measurable tear protein bands ranged from 6 kDa to 85 kDa, using densitometric analysis. Lacrimal gland denervation produced a sustained increase in proteins of 85, 44, and 36 kDa in tears and lacrimal gland tissue from the denervated side, compared with the sham-operated side (0.025 > p > 0.001). The band at 85 kDa was identified as transferrin by Western blot. Tears from the denervated glands also showed transient decreases in low molecular weight tear proteins (18, 12/10, and 6 kDa), as well as a decrease in overall protein concentration, compared with tears from sham-operated glands and non-operated glands (p < 0.001). CONCLUSIONS: These results demonstrate that, in rabbit tears, the quantities of transferrin and two unidentified tear proteins, as well as overall protein concentration, are influenced by the sensory and/or autonomic innervation to the lacrimal gland. The decrease in overall tear protein concentration after lacrimal gland denervation may be related to a loss of nerve-regulated secretagogue-induced protein secretion.

Animals↗
PubMed1987

Neurite outgrowth on cryostat sections of innervated and denervated skeletal muscle.

To localize factors that guide axons reinnervating skeletal muscle, we cultured ciliary ganglion neurons on cryostat sections of innervated and denervated adult muscle. Neurons extended neurites on sections of muscle (and several other tissues), generally in close apposition to sectioned cell surfaces. Average neurite length was greater on sections of denervated than on sections of innervated muscle, supporting the existence of functionally important differences between innervated and denervated muscle fiber surfaces. Furthermore, outgrowth was greater on sections of denervated muscle cut from endplate-rich regions than on sections from endplate-free regions, suggesting that a neurite outgrowth-promoting factor is concentrated near synapses. Finally, 80% of the neurites that contacted original synaptic sites (which are known to be preferentially reinnervated by regenerating axons in vivo) terminated precisely at those contacts, thereby demonstrating a specific response to components concentrated at endplates. Together, these results support the hypothesis that denervated muscles use cell surface (membrane and matrix) molecules to inform regenerating axons of their state of innervation and proximity to synaptic sites.

Animals↗
PubMed1994

Synaptic activity and connective tissue remodeling in denervated frog muscle.

Denervation of skeletal muscle results in dramatic remodeling of the cellular and molecular composition of the muscle connective tissue. This remodeling is concentrated in muscle near neuromuscular junctions and involves the accumulation of interstitial cells and several extracellular matrix molecules. Given the role of extracellular matrix in neurite outgrowth and synaptogenesis, we predict that this remodeling of the junctional connective tissue directly influences the regeneration of the neuromuscular junction. As one step toward understanding the role of this denervation-induced remodeling in synapse formation, we have begun to look for the signals that are involved in initiating the junctional accumulations of interstitial cells and matrix molecules. Here, the role of muscle inactivity as a signal was examined. The distributions of interstitial cells, fibronectin, and tenascin were determined in muscles inactivated by presynaptic blockade of muscle activity with tetrodotoxin. We found that blockade of muscle activity for up to 4 wk produced neither the junctional accumulation of interstitial cells nor the junctional concentrations of tenascin and fibronectin normally present in denervated frog muscle. In contrast, the muscle inactivity induced the extrajunctional appearance of two synapse-specific molecules, the acetylcholine receptor and a muscle fiber antigen, mAb 3B6. These results demonstrate that the remodeling of the junctional connective tissue in response to nerve injury is a unique response of muscle to denervation in that it is initiated by a mechanism that is independent of muscle activity. Thus connective tissue remodeling in denervated skeletal muscle may be induced by signals released from or associated with the nerve other than the evoked release of neurotransmitter.

Acetylcholine↗
PubMed1987

Effect of lack of noradrenaline on myocardial oxygen consumption in denervated dog hearts.

Surgical cardiac denervation was carried out in dogs under halothane anaesthesia. In a paired experimental design control biopsy specimens were obtained before surgical denervation. The dogs were allowed to recover and three weeks to elapse before the second biopsy specimen was taken. Both right and left ventricular specimens had higher in vitro oxygen consumption after denervation than before. Other specimens were immediately cooled in hexane at -60 degrees C and stored under liquid nitrogen until analysed. Succinate dehydrogenase and cytochrome oxidase activities were then measured histochemically in sequential 10 or 12 microns sections. There was no significant difference between the enzyme activities measured before or after cardiac denervation (succinate dehydrogenase 20.3(6.3) before, 19.4(4.02) pmol.H2.cm-2.s-1, after; cytochrome oxidase 223(73.4) before, 263(61.6) (measured as extinction coefficient) after). Thus the changes in oxygen consumption in the chronically denervated dog heart are not due to any lack of these mitochondrial enzymes.

Animals↗
PubMed2001

Specific force deficit in skeletal muscles of old rats is partially explained by the existence of denervated muscle fibers.

We tested the hypothesis that denervated muscle fibers account for part of the specific force (sF(o)) deficit observed in muscles from old adult (OA) mammals. Whole muscle force (F(o)) was quantified for extensor digitorum longus (EDL) muscles of OA and young adult (YA) rats. EDL muscle sF(o) was calculated by dividing F(o) by either total muscle fiber cross-sectional area (CSA) or by innervated fiber CSA. Innervated fiber CSA was estimated from EDL muscle cross sections labeled for neural cell adhesion molecules, whose presence is a marker for muscle fiber denervation. EDL muscles from OA rats contained significantly more denervated fibers than muscles from YA rats (5.6% vs 1.1% of total CSA). When compared with YA muscle, OA muscle demonstrated deficits of 34.1% for F(o), 28.3% for sF(o), and 24.9% for sF(o) calculated by using innervated CSA as the denominator. Denervated muscle fibers accounted for 11.3% of the specific force difference between normal YA and OA skeletal muscle. Other mechanisms in addition to denervation account for the majority of the sF(o) deficit with aging.

Aging↗
PubMed2002

Effects of long-term denervation on skeletal muscle in old rats.

We compared the reactions to denervation of limb muscles between young adult and old rats. After denervation for up to 4 months in 24-month-old rats, limb muscles were removed and analyzed for contractile properties, morphology, and levels of several key molecules, including the peptide elongation factors eEF1A-1 and eEF1A-2/S1, myogenin, gamma-subunit of the acetylcholine receptor, and cyclin D3. The principal difference between denervated old and young muscle is a somewhat slower rate of atrophy in denervated older muscle, especially among the type II fibers. Expression levels of certain molecules were higher in old than in young control muscle, but after denervation, levels of these molecules increased to the same absolute values in both young and old rats. Although many aspects of postdenervation reactions do not differ greatly between young and old animals, the lesser degree of atrophy in the old rats may reflect significant age-based mechanisms.

Age Factors↗
PubMed2003

Expression of ARPP-16/19 in rat denervated skeletal muscle.

It is known that denervation of rat skeletal muscle causes atrophy and this is often adopted as a model for human muscle atrophy. To understand the molecular changes that occur, it is important to identify the profiles of differential gene expression. In the present study, we investigated differentially expressed genes in denervated muscle using DNA microarrays with printed genes preferentially expressed in skeletal muscle. We found that several genes are differentially expressed. Of these genes, ARPP-16/19 (cAMP-regulated phosphoprotein 16/19) is selectively enhanced after denervation. The expression of ARPP-16/19 in denervated muscles starts to increase from two days after denervation surgery. On the other hand, the expression of ARPP-16/19 does not change in hind-limb suspended muscles, such as EDL and soleus muscles. These results suggest that the increase in ARPP-16/19 mRNA expression is regulated by unknown factor(s) secreted from nerves, and not by electrical muscle activity.

Animals↗
PubMed2005

Denervation enhances the expression of SHPS-1 in rat skeletal muscle.

SHPS-1 (Src homology 2 domain containing protein tyrosine phosphatase substrate 1) is a transmembrane glycoprotein containing three immunoglobulin-like motifs in its extracellular domain and immunoreceptor tyrosine-based inhibitory motifs (ITIM) that interact with SHP-2 (Src homology 2 domain containing protein tyrosine phosphatase-2) in its cytoplasmic region. SHPS-1 is highly expressed in brain, but at much lower levels in skeletal muscle. In this study, we found that the level of the SHPS-1 mRNA increases in rat skeletal muscle after denervation. Western blot analysis also confirmed the increase of SHPS-1 in denervated muscle. Moreover, it was found that the glycosylation of SHPS-1 is N-linked in a muscle-specific manner, and that this is altered upon innervation or denervation. Immunohistochemistry revealed SHPS-1 immunoreactivity at neuromuscular junctions (NMJs) under innervation, whereas immunoreactivity was observed extrasynaptically in muscle fibers after denervation. Our results indicate that the expression, glycosylation, and localization of SHPS-1 are strongly regulated by the nervous system, and that SHPS-1 may play an important role in denervated skeletal muscle.

Animals↗
PubMed2004

Chronic renal denervation prevents glomerular hyperfiltration in diabetic rats.

BACKGROUND: The increase in glomerular filtration rate (GFR) induced by amino acid infusion is attenuated in rats with chronic renal denervation. The aim of the present study was to investigate whether renal denervation abrogates glomerular hyperfiltration occurring in the early state of diabetes mellitus. METHODS: Sprague-Dawley rats were subjected to bilateral renal denervation before induction of diabetes mellitus (DM) by streptozotocin. Clearance experiments were performed 2 weeks after onset of moderate DM. Glomerular volume was estimated following paraformaldehyde fixation in rat kidney slices from measurement of cross-sectional area of Bowman's capsule. RESULTS: GFR in non-diabetic rats with intact nerves (CON-INN) was 0.82+/-0.03 ml.min(-1).100 g(-1) body weight. Diabetic animals with innervated kidneys presented a significant glomerular hyperfiltration (1.13+/-0.03 ml.min(-1).100 g(-1) body weight), while renal denervation in diabetic rats lowered GFR towards levels of CON-INN (0.88+/-0.03 ml.min(-1).100 g(-1) body weight). Estimated glomerular volume amounted to 0.69+/-0.03.10(6) micro m(3) in the CON-INN group and was significantly higher in diabetic animals with intact renal nerves (0.86+/-0.04.10(6) microm(3)). Interestingly, renal denervation prevented the glomerular enlargement due to DM. CONCLUSIONS: Renal nerves appear to be significantly involved in the mediation of glomerular hyperfiltration in experimental DM. If the kidney is prevented from sympathetic nerve stimulation, structural changes due to early diabetic nephropathy, i.e. glomerular enlargement, are abolished.

Analysis of Variance↗
PubMed1999

Subcutaneous feather tract denervation does not alter feather retention force ante- and postmortem in broilers.

To determine whether feather retention force (FRF) in 6-wk-old commercial broilers was influenced by the presence or absence of cutaneous innervation, nerve trunks for the pectoral and sternal feather tracts were severed unilaterally (left side) in Trial 1. In Trial 2, the sternal subcutaneous nerve trunk was severed either unilaterally (left or right side) or bilaterally. Four days postdenervation, FRF was determined bilaterally either antemortem (immediately prior to stunning) or 2 min after stunning and bleeding (postmortem). In Trial 1, the pectoral feather tract ante- and postmortem FRF values did not differ significantly for innervated or denervated tracts. In this trial, the sternal feather tract ante- and postmortem FRF values were 13% higher (44 g) for the denervated (left side) than for the innervated (right side) treatments. Partitioning this difference into the effects of sample side or innervation could not be attained because only the left side was denervated (left-denervation or right-innervated) in Trial 1. In Trial 2, both the left and right sternal feather tracts were represented in equal numbers for the innervated and denervated treatments, and there were no significant differences in FRF related to innervation, left and right side, or ante- and postmortem sample times. The presence or absence of cutaneous nerve innervation does not appear to influence FRF ante- or postmortem. This finding indicates that treatments disabling the central nervous system antemortem may lower FRF indirectly by altering cutaneous metabolism and therefore have been consistently unsuccessful in substantially altering postmortem FRF.

Animals↗