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PubMed2005

Denervation of the porcine ovaries performed during the early luteal phase influenced morphology and function of the gonad.

We studied both morphology and steroidogenic activity of ovaries in gilts after bilateral surgical denervation performed on day 3 of the estrous cycle. Blood samples were collected from day 4 of the first estrous cycle to day 11 of the subsequent cycle. Denervation resulted in a dramatic reduction in the number or in the disappearance of tyrosine hydroxylase/dopamine-beta-hydroxylase- and/or neuropeptide Y-immunoreactive nerve fibres. On day 11 of the second cycle, the number of follicles (3-6 mm in diameter) was lower (p<0.001) in the denervated ovaries, while corpora lutea were not present. Neurectomy also led to a decrease in the concentrations of progesterone, androstendione and 17beta-estradiol in the follicular fluid originated from small (1-3 mm in diameter) as well as medium-sized follicles (3-6 mm in diameter). Similar to follicular fluid, concentration of androstendione in the follicular wall of medium-sized follicles decreased in experimental gilts in comparison to that of control animals. In addition, plasma concentrations of LH and steroid hormones were lower in the control than in the experimental group. Our results show that denervation of ovaries during the early luteal phase of the estrous cycle in gilts resulted in the changes in both morphology and steroidogenic activity. These results confirm the important role of the peripheral nerves in the function of ovaries.

Androstenedione↗
PubMed1992

[Effect of trigeminal denervation on rabbit corneal epithelium].

To investigate the effects of trigeminal denervation on the corneal epithelium, left postganglionic trigeminal neurotomy via intracranial approach was performed in 22 rabbits. Among 16 rabbits survived successfully, 13 denervated eyes (81%) showed corneal epithelial abnormalities that included 4 epithelial defects and 9 epithelial opacities. The remaining 3 eyes were normal. Histological examination showed many atrophic epithelial cells and the thinning of the corneal epithelial layer in the denervated eyes with corneal opacities. There was no abnormality in corneal stroma or endothelium. The ratio of epithelial to total corneal thickness calculated by a computer-assisted image analyzer was 6.5 +/- 2.1 (%) in control eyes and 3.8 +/- 1.9 (%) in the denervated eyes, the two values being significantly statistically different (p less than 0.001).

Animals↗
PubMed2006

[Impacts of denervation on the morphology and expression of neuronal nitric oxide synthase of prostate of adolescent rats].

OBJECTIVE: To explore the impacts of denervation on the morphology and the expression of neuronal nitric oxide synthase (nNOS) of prostate of the adolescent rats. METHODS: Adolescent male SD rats were randomly divided into group A and group B. The right pelvic ganglion denervation was performed in group B with the help of surgical microscope, and group A received a sham operation. Five weeks later, the ventral prostates were obtained for morphologic observation, apoptosis detection and the evaluation of nNOS expression. RESULTS: A 30.8% reduction of right ventral prostate (RVP) fresh weight was found in group B. After denervation, histological features showed an overall decrease in the numbers of cells and cell height, and apoptosis indexes (AI) was significantly higher than that in group A (P <0.01), while the expression of nNOS decreased apparently (P < 0.01). CONCLUSION: The study indicates that denervation can cause apoptosis of the prostatic, and affect the prostate growth of the adolescent rat. During this process, nNOS plays an important role in the regulation of apoptosis.

Animals↗
PubMedDate not supplied

[Elevation of the vascular smooth muscle sensitivity to effects of constrictors after denervation and under decreased blood pressure].

Changes in contractile activity of saphenous artery in normotensive rats and in rats with regional hypotension have been investigated. The abdominal aorta was partially occluded in Wistar rats distally to the renal arteries. Four weeks later, a 5-7-mm segment of the femoral nerve in one hindlimb was resected to denervate the saphenous artery. After two weeks, the isometric contraction of innervated and denervated saphenous artery segments was studied. In normotensive rats, the denervation augmented vessel sensitivity to noradrenaline, phenylephrine, serotonin, and KCl (in the presence of phentolamine). Chronic hypotension also augmented vessel sensitivity to constrictor agonists, whereas denervation did not result in further increase of sensitivity. In glyoxilic acid-stained preparations obtained from hypotensive rats, a reduced intensity of fluorescence of adrenergic fibers was observed. It was assumed that the higher sensitivity of vascular smooth muscle in hypotensive rats is due to functional disturbances of sympathetic innervation.

Animals↗
PubMed1991

The molecular and pharmacological properties of muscarinic cholinergic receptors expressed by rat sweat glands are unaltered by denervation.

Previous studies have indicated that denervation of adult rodent sweat glands results in the loss of secretory responsiveness to muscarinic agonists. To elucidate the molecular basis of this loss, we have characterized the muscarinic cholinergic receptor present in adult rat sweat glands and examined the effects of cholinergic denervation on its properties and expression. When homogenates of gland-rich tissue from adult animals were assayed with [N-methyl-3H]-scopolamine, a high-affinity muscarinic antagonist, the concentration of muscarinic receptors was 301 fmol/mg protein and the affinity was 131 pM. Autoradiographic analysis demonstrated that ligand binding sites were detectable only on glands. In competition studies with well-characterized muscarinic agents, the receptor exhibited typical muscarinic pharmacology. Further investigation with the selective muscarinic antagonists 4-diphenylacetoxy-N-methylpiperidine methiodide, pirenzepine, and AF DX-116 revealed that the sweat gland receptor belongs to the M2 glandular pharmacological subtype. In situ hybridization histochemistry with receptor subtype-specific oligonucleotide probes indicated that rat sweat glands express the m3 molecular receptor subtype. Seven days after sciatic nerve transection, when denervated glands were compared to those on the contralateral unoperated side, there was no significant difference either in the concentration or affinity of muscarinic binding sites or in receptor density or distribution. Furthermore, the molecular subtype and the level of its expression were unchanged. Thus, it appears that muscarinic binding sites and m3 receptor mRNA are present in denervated sweat glands that are unresponsive to muscarinic stimulation. These results suggest that the regulation of responsiveness occurs at a point distal to the expression of muscarinic receptors.

Animals↗
PubMed1991

Renal denervation enhances the phosphaturic effect of parathyroid hormone.

Hyperventilation/hypocapnia increases renal phosphate reabsorption and decreases the phosphaturic effect of parathyroid hormone (PTH). Recent studies suggest that the blunted phosphaturic effect of PTH in hyperventilated/hypocapnic rats may be mediated by the stimulation of renal beta-adrenoreceptors. In the present study, no differences in plasma catecholamine levels were detected in hyperventilated/hypocapnic rats as compared to hyperventilated/normocapnic rats. Therefore, studies were performed to determine the role of the renal nerves in the blunted phosphaturic effect of PTH in hyperventilated/hypocapnic rats. In clearance experiments in acutely thyroparathyroidectomized male Sprague-Dawley rats, PTH infusion increased the fractional excretion of phosphate (FEPi) in the denervated left kidney of hyperventilated/hypocapnic rats (n = 8), from 2.4 +/- 1.1 to 18.6 +/- 2.7%, as compared to 1.0 +/- 0.3 to 9.1 +/- 2.1% in the contralateral innervated kidney. Denervation of the left kidney in hyperventilated/normocapnic rats (n = 8) also significantly increased the phosphaturic response to PTH by 2.5 +/- 1.5 to 26.9 +/- 3.0% as compared to 0.9 +/- 0.5 to 18.6 +/- 2.6% in the contralateral innervated kidney. The phosphaturic responses to PTH were similar when comparing the denervated kidney in hyperventilated/hypocapnic rats with the innervated kidney of hyperventilated/normocapnic rats. Thus, renal denervation enhanced the phosphaturic effect of PTH in both hyperventilated/hypocapnic and hyperventilated/normocapnic rats. These results suggest that renal nerves play a role in the modulation of the phosphaturic effect of PTH.

Animals↗
PubMed1991

Effect of renal denervation on the development of hypertension in Dahl-Iwai salt-sensitive rats.

Renal denervation has been shown to delay the onset of hypertension in spontaneously hypertensive rats and DOCA-salt sensitive rats. We investigated the contribution of the renal nerves to the development of hypertension in Dahl-Iwai salt-sensitive (DS) rats. Bilateral renal denervation or sham-operation was carried out in DS rats, and animals were then kept on a high salt diet (study I) or on a normal salt diet (study II). DS rats became severely hypertensive (207 +/- 8 mmHg) after 4 weeks on a high salt diet. They became mildly hypertensive (156 +/- 3 mmHg) after 4 weeks on a normal salt diet. In both studies, renal denervation exerted no effect on the development of hypertension in the DS rats. The urinary sodium excretion, urinary volume, heart rate and body weight were unaltered by renal denervation. These results indicate that the renal nerves do not make a major contribution to the development of hypertension in DS rats.

Animals↗
PubMed1990

Denervation of mouse skeletal muscle differentially affects the expression of the jun and fos proto-oncogenes.

The mRNA levels of the jun and fos proto-oncogenes, whose products are part of the transcription regulatory complex AP1, were investigated after denervation of the lower-leg muscles of adult mice. The levels of the four transcripts studied varied in a non-coordinated manner after muscle denervation. As early as 1.5 h after sciatic nerve section, c-fos mRNA reached a maximum and then returned to basal level at 6 h, while c-jun and jun-B mRNA levels increased after 24 h and remained elevated for at least 8 days. In contrast, jun-D mRNA levels did not change after denervation. In situ hybridization experiments revealed different patterns of spatial localization of the c-jun and jun-D transcripts. Labeling of dividing cells by the thymidine analog bromo-deoxyuridine demonstrated that proliferating cells were at least 40-fold less abundant than those expressing c-jun. Thus, denervation rapidly and differentially modulates the expression of genes coding for the AP1 transcription factor subunits in differentiated muscle cells. The possibility that these proto-oncogenes might be involved in the trans-synaptic regulation of muscle-specific gene expression is discussed.

Animals↗
PubMed1990

Sodium and bicarbonate reabsorption in microperfused proximal tubules from the denervated rat kidney: relationship to cortical Na-K-ATPase activity.

Although numerous studies have documented the effects of the renal nerves on kidney function, the mechanisms involved in the diuresis have yet to be elucidated. The present study was undertaken to examine the effect of acute unilateral renal denervation (DNX) on proximal tubular absorption of fluid and bicarbonate and to determine if acute DNX was associated with changes in Na-K-ATPase activity. Acute DNX caused significant increases in urine flow and absolute and fractional excretions of Na, HCO3 and K compared to the contralateral control kidney (INN) or sham denervated kidneys in normal rats as well as in rats made alkalotic by the I.V. infusion of 150 mM NaHCO3. These effects were seen without significant changes in GFR. When proximal convoluted tubules (PCT) were perfused with bicarbonate-Ringer's solution DNX resulted in a 67% decrease in fluid reabsorption (INN: 3.0 +/- 0.2 vs DNX: 1.0 +/- 0.1 nl/min/mm; p less than 0.001) and a 40% decline in bicarbonate (total CO2) reabsorption (INN: 151.3 +/- 8.8 vs DNX: 94.5 +/- 10.1 pmol/min/mm; p less than 0.01). Acute DNX caused a significant reduction in Na-K-ATPase activity measured in microsomes derived from the outer cortex of the kidney (INN: 13.2 +/- 1.3 vs DNX: 10.9 +/- 0.7 mumol PO4/mg prot/hr; p less than 0.01) while Mg-ATPase was unaffected. Sham denervation had no effect on any of the above parameters. These results indicate that the renal nerves play an important role in the regulation of bicarbonate and fluid reabsorption in the PCT. The diuresis, natriuresis, and bicarbonaturia associated with acute unilateral renal denervation may be the direct result of inhibition of Na-K-ATPase activity.

Acid-Base Equilibrium↗
PubMed1990

Age differences in morphology of reinnervation of partially denervated mouse muscle.

The effect of age on the ability of motor neurons to develop and maintain an enlarged total axonal and synaptic volume was compared in soleus muscles of 5-8-month and 25-30-month mice, 30-120 d after partial denervation. Before and after partial denervation (transection of the L5 root), the total number of muscle fibers was the same in all muscles. However, in young animals, there was only some transient atrophy and hypertrophy mostly receded by 120 d, whereas in old muscle, a more prominent early atrophy was followed by persistent hypertrophy. Ectopic endplates were not found. In zinc-iodide-osmium (ZIO) stained preparations, muscle fibers with small nerve terminals were present at 60 d and were still present in old muscle at 120 d. Fluorescent staining of nerve terminals and acetylcholine receptors revealed that in young muscle, postsynaptic sites were nearly or completely reoccupied by 60 d. In old muscle, about 22% of former junctions were denervated, with the remainder minimally to fully reinnervated. At 60 d and thereafter, collateral sprouts originated from nodes of Ranvier in both young and old muscle and were remyelinated in young but mainly unmyelinated and remarkably tortuous in old animals. These results, confirmed with immunofluorescent strains for myelin basic protein and neurofilaments, account for many of the physiological findings (Jacob and Robbins, 1990). Motor unit size expanded 2.5 times in young and 2 times in old muscle at 60 d after partial denervation. However, the increment in total quantal output and nerve terminal volume per motor neuron was 60-100% greater than control in young but only 20-25% greater in old muscle, with little further recovery. This inability of the motor neuron in old mice to expand the field of innervation may reflect a limitation imposed by reduced axonal transport. The present findings may elucidate the muscle weakness in postpolio syndrome and amyotrophic lateral sclerosis.

Aging↗
PubMed1989

Nondopaminergic prefrontocortical efferent fibers modulate D1 receptor denervation supersensitivity in specific regions of the rat striatum.

A unilateral injection of 6-OHDA (6 microgram/1.5 microliter) was made into the fields of Forel in order to estimate the effects of the destruction of ascending dopaminergic (DA) pathways on the denervation supersensitivity of DA D1 receptors in the rat striatum. DA-sensitive adenylate cyclase activity was markedly enhanced in the anteromedian part of the striatum 3 weeks after the lesion (+68%) and remained elevated for several weeks thereafter (+36%). A different response occurred in the laterodorsal striatum, where the increase in DA-sensitive adenylate cyclase activity was less pronounced after 3 weeks (+40%) and no longer present after 7 weeks. Estimations of catecholamine levels indicated that the lesion made destroyed not only nigrostriatal DA neurons but other ascending catecholaminergic fibers projecting into the cerebral cortex as well. In addition, retrograde transport experiments made with wheat germ agglutinin coupled to horseradish peroxidase indicated that the anteromedian part of the striatum, but not the laterodorsal one, receives both an ipsi- and contralateral cortical projection originating in the prefrontocortical DA field. When the destruction by 6-OHDA of this contralateral DA innervation was combined to the unilateral lesion of the fields of Forel, the increase in DA-sensitive adenylate cyclase activity in each striatal area 3 or 7 weeks postlesion was prevented. This effect was due to DA denervation of the prefrontal cortex since striatal D1 denervation supersensitivity was still observed when contralateral ascending noradrenergic fibers were selectively destroyed by a 6-OHDA lesion made laterally to the pedunculus cerebellaris superior. These results suggest that, by controlling the activity of corticostriatal neurons, the mesocorticoprefrontal DA neurons exert a permissive role on the development of D1-receptor denervation supersensitivity in specific areas of the striatum.

Adenylyl Cyclases↗
PubMed1978

[Excretory function of the kidney after denervation and the administration of a beta-blockader].

Osmotic diuresis (15% mannitol, 4.5 ml/hr) was in duced in anesthetized rats. At the end of each of 10 consecutive 10-min clearance periods the following parameters were determined: diuresis, sodium, chlorine and osmotic excretion, GFR (inulin clearance). The animals were divided into three groups: a) controls, b) with bilateral renal denervation (performed one week earlier) and c) with application of beta-adrenergic blocking agent propranolol (Obsidan, Germed DDR) introduced intravenously 0.1 mg/100 g initially and 0.12 mg/100 g sustaining dose during 2 hrs. The experimental results showed an increased sodium excretion in denervated and obsidan--treated animals with no change of the total excreted osmotically active substances. In denervated animals the chlorine excretion was increased as well. The data suggest that, in osmotic diuresis, the renal denervation and beta-adrenergic blocking agents inhibit the tubular sodium transport. The kidney osmoregulatory functions remains unchanged.

Adrenergic beta-Antagonists↗
PubMed1989

Regulation of muscarinic receptors in hippocampus following cholinergic denervation and reinnervation by septal and striatal transplants.

The regulation of hippocampal muscarinic M1 and M2 receptors was studied by autoradiographic methods following cholinergic denervation and reinnervation from embryonic septal transplant. In young adult male rats the density of M1 sites, labeled either with 3H-pirenzepine (PZ) or 3H-N-methylscopolamine (NMS, in the presence of excess carbachol), exceeded by 4- to 5-fold the density of M2 sites, labeled with 3H-NMS in the presence of excess PZ. Both receptors appeared to be densest in hippocampal regions lowest in acetylcholinesterase or 3H-hemicholinium-3 binding. The distribution of M1 receptors did differ from the distribution of M2 receptors within subregions of the hippocampus. Along the mediolateral axis from the subiculum to the lateral CA 1, the density of M1 receptors is uniform, but the density of M2 receptors decreases. Also apparent is the relatively small difference in density between the CA1 and dentate gyrus for M1 receptors but a significantly greater difference for M2 receptors. However, the response of M1 and M2 receptors to long-term cholinergic denervation following fimbriafornix transection of the septal cholinergic input and to cholinergic innervation by embryonic septal transplants was similar. Long-term denervation (40-60 d) resulted in a 30-60% increase in both M1 and M2 receptors within regions of the hippocampal formation. Receptor levels were reduced to normal in regions innervated by septal transplants. For both receptors, the changes in the density of sites were due to alterations in the Bmax and not the Kd for the radioligands. The specificity of this regulation is supported by the evidence that (1) the degree and topography of the normalization of muscarinic receptor density was entirely dependent on the degree and pattern of cholinergic reinnervation by the fibers of the septal transplant, (2) cholinergic fiber reinnervation by embryonic striatal grafts also down-regulated the density of M1 and M2 receptors, and (3) successfully surviving transplants (e.g., cerebellar and striatal) that did not provide innervation to the hippocampus did not induce down-regulation of muscarinic receptors. Changes in the density of sites were not related to changes in the width of the hippocampus following denervation and reinnervation. The data support the view that the majority of M1 and M2 receptors are located postsynaptically on neurons within the hippocampus and not presynaptically on cholinergic fibers.

Animals↗
PubMed1989

Effect of short time denervation on intracellular elemental content and fibre atrophy pattern of slow and fast twitch rat muscle.

Fast twitch extensor digitorum longus (EDL) and slow twitch soleus (S) muscles were studied after 5 and 16 days of denervation. Elemental contents of single muscle fibres were obtained with energy dispersive X-ray microanalyses (XRMA) applied on cryosections visualised in the scanning or scanning-transmission mode of electron microscopy. Cross sections in series with those produced for analytical electron microscopy were stained for enzyme histochemical fibre typing. A similar increase of Na and Cl was observed in EDL and S fibres after 16 days of denervation and a decrease of K was observed as well in EDL. This time after denervation is known to correspond to the maximal acetylcholine receptor synthesis extrajunctionally. There were no changes of elemental content after 5 days and thus the early membrane changes as i.a. fall in resting membrane potential and increased permeability for Na as well as increased endocytosis did not correspond to changes detectable by XRMA. Time course of atrophy differed between histochemical fibre types in EDL. In S all the muscle fibres atrophied earlier than in EDL and without any difference between fibre types. Then changes in elemental composition of muscle fibres after denervation do not seem to be related to degree and time course of muscle fibre atrophy.

Animals↗
PubMed1986

In vitro and in vivo activation of the insulin receptor kinase in control and denervated skeletal muscle.

Skeletal muscle rapidly develops severe insulin resistance following denervation, although insulin binding is unimpaired. Insulin-stimulated receptor tyrosyl kinase activity was studied in intact and 24-h denervated rat hind limb muscles using three preparations: (a) solubilized insulin receptors incubated +/- insulin with gamma-[32P]ATP and histone H2b; (b) soleus muscles prelabeled in vitro with [32P]phosphate with subsequent insulin-stimulated phosphorylation of the receptor in situ; (c) assessment of in vivo activation of muscle receptor tyrosyl kinase by insulin. The latter was achieved by solubilizing muscle insulin receptors in the presence of phosphoprotein phosphatase and kinase inhibitors and measuring receptor-catalyzed histone H2b phosphorylation in the presence of limiting (5 microM) gamma-[32P]ATP. Receptors isolated 5 and 30 min after intravenous insulin injection catalyzed 32P incorporation into histone H2b twice as fast as those from saline-treated controls; insulin stimulated histone H2b labeling exclusively on tyrosine. In vivo activation was demonstrated using solubilized and insulin-agarose-bound receptors. Autophosphorylation of the beta-subunit and receptor tyrosyl kinase activity toward histone H2b was stimulated by insulin in denervated muscles as in controls, although the biological response to insulin, in vitro and in vivo, was markedly impaired after denervation, suggesting a postreceptor defect. The method developed to assess insulin-stimulated receptor activation in vivo seems useful in characterizing mechanisms of insulin resistance.

Animals↗
PubMed1988

Modification of electrocyte membrane lipid composition induced by denervation.

1. We determined the effect of denervation on the lipid composition of the main electric organ and electrocyte postsynaptic membrane vesicles of Electrophorus electricus. 2. Lipid extracts of whole electric organ contain mainly cholesterol, triglycerides, phosphatidylcholine and phosphatidylethanolamine. After 30 days of denervation, the lipid composition of whole electric organ did not change appreciably. 3. Lipid extracts of the membrane vesicles were similar, except that they contained mainly free fatty acids rather than triglycerides. After 30 days of denervation, cholesterol concentration was increased and phospholipids were decreased in the membrane fraction, with higher relative concentrations of phosphatidylethanolamine and cerebrosides. 4. These results suggest that electrocyte membrane fluidity and permeability will change after 30 days of denervation.

Animals↗
PubMed1978

[Effect of olivomycin on denervation changes in the membrane of frog tonic muscle fibers].

Membrane properties of frog denervated tonic muscle fibers were investigated after the action of olivomycin, which is an inhibitor of protein synthesis. Olivomycin injected as a single dose (7.5 mg) during 1--2 days after the denervation of m. pyriformis decreases the regenerative action potentials. This action is decreased three weeks after denervation. After denervation, olivomycin failed to prevent the appearance of extrajunctional cholinoergic receptors, but blocked the increase of junctional ones. The data support the view that some neuronal factor may influence the synthesis of functional membrane proteins.

Animals↗
PubMedDate not supplied

Phrenic output changes due to progressive airway denervation in rabbits.

The experiments were performed with thirteen anaesthetized rabbits breathing spontaneously through the larynx. Phrenic output was measured during tidal respiration in control conditions and in the course of progressive denervation of the laryngeal and tracheobronchial compartments. We have analysed changes in amplitude and the rate of rise of the integrated phrenic neurogram as well as the changes in TI, TE, TT and f of the respiratory timing after superior laryngeal nerves (SLN-s) section, section of the recurrent laryngeal nerves (RLN-s) and step-wise complete midcervical vagotomy. Nerve sections were performed by two methods: 1) bilateral SLN-s, RLN-s and cervical vagal neurotomy (horizontal method); 2) right-sided neurotomies of SLN, RLN and vagus followed by left-sided neurotomies of these nerves (vertical method). Laryngeal deafferentation did not greatly affect respiratory variables. Unilateral and especially bilateral vocal cord paralysis prolonged the respiratory cycle with enhanced TI/TT ratio, increased amplitude and rate of rise of the integrated phrenic neurogram. Maximum values of all parameters (the rate of rise excluded) were achieved after complete midcervical vagotomy. Of the two methods of denervation, the right-sided followed by left-sided denervation led to better adaptation of the organism to the respiratory disturbance (smaller changes in TI and TE compared with the control values). Denervation by the 'horizontal' method (paired section of the nerves) led to an abrupt failure of effective ventilation.

Animals↗