Developmental delay of lingual lipase expression after guanethidine-induced sympathectomy.

Rat lingual lipase increases during postnatal development. To evaluate the role of the sympathetic nervous system in the control of lingual lipase during development, suckling rats were chemically sympathectomized by chronic treatment with guanethidine. This treatment was found to be effective in suppressing the developmental increase of lingual lipase. The effect was age dependent and also related to the dose of guanethidine given (i.e., the higher the dose, the more effective the suppression is, up to 40 micrograms/g body wt). The effect of guanethidine on lingual lipase suppression was not a result of induced stress, since simultaneous treatment with RU-38486, a known glucocorticoid receptor antagonist, did not prevent the decrease in lingual lipase activity. Ephedrine, a known sympathomimetic agent, restored the lingual lipase to a near normal level in guanethidine-treated animals, confirming that guanethidine acts through the sympathetic nerves. Furthermore, histochemical studies showed that guanethidine-treatment resulted in the reduction or elimination of catecholaminergic fibers in the von Ebner's glands. The effect of guanethidine was found to be transient, in that the lingual lipase activity showed complete recovery upon withdrawal of the treatment for 1 week. Together, the results indicated that sympathetic nerves have an important regulatory role in lingual lipase in rat pups during development.     

Histochemical evidence of chemical sympathectomy by guanethidine in newborn rats

Synopsis Guanethidine is known to cause a loss of catecholamines from sympathetically innervated tissues and sympathetic ganglia in adult animals but its effect on newborn animals has not been examined.Newborn rats were injected daily with guanethidine (20 mg/kg body weight) for 8 days. They were killed when 1 month-old along with untreated litter mate controls. Catecholamines were demonstrated in the iris, in the pineal body and in sympathetic ganglia, using the formaldehyde-induced fluorescence method.In the guanethidine-treated rats there was a complete loss of fluorescent nerve fibres from the pineal body and an almost complete loss of similar fibres from the iris. The sympathetic ganglia were reduced to less than 10% of the control ganglia, and the number of nerve cell bodies per unit area was decreased in the ganglion remnants.It is concluded that guanethidine causes, in newborn rats, an irreversible destruction of most sympathetic neurons, i.e. a chemical sympathectomy closely resembling that obtainable in newborn animals by injections of 6-hydroxydopamine or antiserum to nerve growth factor.     

Blockade of the sympathetic nervous system degrades ligament in a rat MCL model.

We hypothesize that blockade of the sympathetic nervous system degrades ligament. We tested this hypothesis in a rat medial collateral ligament (MCL) model. Fifteen animals were treated for 10 days with the sympathetic chemotoxin guanethidine using osmotic pumps, whereas 15 control rats received pumps containing saline. A reduction in plasma concentrations of norepinephrine in the guanethidine rats indicated a significant decrease in sympathetic nerve activity. Vasoactive intestinal peptide and neuropeptide Y were decreased in MCLs from guanethidine animals, as quantified by radioimmunoassays. Tissue vascularity was substantially increased in guanethidine MCLs, whereas mechanical properties were significantly decreased. Proteases, such as matrix metalloproteinases (MMP) and cysteine proteases, play a major role in ligament degradation. The proteases MMP-13, cathepsin K, and tartrate-resistant acid phosphatase (TRAP) have collagenolytic activity and have been shown in rat ligament tissues. To determine whether the degradation seen in this study was due to protease activity, we determined the expression of these enzymes in control and treated MCLs. Real-time quantitative PCR revealed that guanethidine treatment increased expression of MMP-13 and cathepsin K mRNAs, although overall expression levels of MMP-13 and TRAP were relatively low. Histology also identified increases in TRAP and cathepsin K, but not MMP-13, in guanethidine-treated tissues. Results support our hypothesis that blockade of the sympathetic nervous system substantially degrades ligament.     

Tumor necrosis factor, interleukin-1 and interleukin-8 mediate the nociceptive activity of the supernatant of LPS-stimulated macrophages

It has been suggested that the supernatant of LPSstimulated macrophages (macrophage nociceptive factor, MNF) promotes nociception in mice. Intraperitoneal administration of MNF induced dose-related writhing, which reached a plateau between 18 and 26 min after injection and decreased within 60 min. The release of MNF was inhibited by the pretreatment of the macrophages with cycloheximide, a protein synthesis inhibitor, or with the glucocorticoid dexamethasone. Cyclooxygenase inhibitors, such as indomethacin or paracetamol, had no effect. The MNF-induced nociception was inhibited in a dose-related manner by pretreatment of the animals with indomethacin, paracetamol or dexamethasone. Pretreatment of the animals with the sympatholytics guanethidine and atenolol partially reduced the MNF nociception, which was abolished by the combination of guanethidine or atenolol with indomethacin. The preincubation of MNF with antisera against TNF-alpha, IL-1 or IL-8 partially inhibited its nociceptive effect. Intraperitoneal injection of a mixture of the recombinants cytokines TNF-alpha, IL-1 and IL-8 mimicked MNF nociception. The individual injection of these cytokines was unable to induce the nociceptive effect. In conclusion, our data suggest that the nociceptive activity of the supernatant of LPSstimulated macrophages is explained by the presence of TNF-alpha, IL-1 and IL-8, the nociceptive activity of which (in mice) seems to be due to the release of cyclooxygenase and sympathetic metabolites.     

Reduction in human urinary MHPG excretion by guanethidine: urinary MHPG as index of sympathetic nervous activity.

The norepinephrine metabolites methoxyhydroxyphenyl glycol (MHPG) and vanillylmandelic acid (VMA) were measured in the urine of hypertensive subjects before and during adminstration of guanethidine, a peripheral sympatholytic agent which does not cross the blood-brain barrier or deplete adrenal catecholamines. Dosages of guanethidine (1.2 mg/kg/day) sufficient to cause at least a 20 torr reduction in standing systolic blood pressure caused a mean 63% (maximum of 68%) reduction in urinary MHPG excretion (p=0.01) while only causing a mean 37% (maximum of 44%) reduction (p<0.005) in excretion of VMA. These results indicate that MHPG in human urine, as in lower animals, is predominantly the product of peripheral sympathetic nervous system, rather than central nervous system nonrepinephrine metabolism. Urinary MHPG is more sensitive to specific sympatholytic therapy than is urinary VMA, and may be a useful index of sympathetic nervous activity.     

Changes in cardiac rhythm of rats in dehydration

80 mongrel rats were studied for peculiarities of the heart activity regulation in dehydration, conditions of the vegetative homeostasis being different. Data of the variation pulsometry were used. A sympathetic shift of the vegetative homeostasis was a common dehydration-caused response. The shift was significant in rats with an initial equilibrium of the vegetative homeostasis and prevailing parasympathetic effects. The survival rate of this group of rats was high. In the group of rats with the initial prevalence of a sympathetic tonus a short-term sympathetic shift was replaced by an increase of parasympathetic effects. The survival rate of this group was much lower. Therefore, rats with initial prevalence of the sympathetic compartment tonus of the vegetative nervous system are more labile to the effect of the dehydration stress.     

Marked difference in the susceptibility of several species to guanethidine-induced chemical sympathectomy.

Administration of high doses of guanethidine to newborn or adult rats destroys the sympathetic nervous system. In an attempt to produce models of permanent sympathectomy in other species, high doses of guanethidine were administered neonatally to cats, rabbits, and hamsters. In contrast to rats, the sympathetic nervous systems of these species were not destroyed by guanethidine.     

Restraint stress delays solid gastric emptying via a central CRF and peripheral sympathetic neuron in rats

Central corticotropin-releasing factor (CRF) delays gastric emptying through the autonomic nervous system. CRF plays an important role in mediating delayed gastric emptying induced by stress. However, it is not clear whether a sympathetic or parasympathetic pathway is involved in the mechanism of central CRF-induced inhibition of solid gastric emptying. The purpose of this study was to investigate whether 1) CRF inhibits solid gastric emptying via a peripheral sympathetic pathway and 2) stress-induced inhibition of solid gastric emptying is mediated via a central CRF and peripheral sympathetic pathways. Using male Sprague-Dawley rats, CRF was injected intracisternally with or without various adrenergic-blocking agents. To investigate whether central CRF-induced inhibition of solid gastric emptying is mediated via a peripheral sympathetic pathway, rats underwent celiac ganglionectomy 1 wk before the gastric emptying study. After solid meal ingestion (90 min), gastric emptying was calculated. To investigate the role of endogenous CRF in stress-induced delayed gastric emptying, a CRF type2 receptor antagonist, astressin2-B, was intracisternally administered. Rats were subjected to a restraint stress immediately after the feeding. Intracisternal injection of CRF (0.1-1.0 microg) dose-dependently inhibited solid gastric emptying. The inhibitory effect of CRF on solid gastric emptying was significantly blocked by guanethidine, propranolol, and celiac ganglionectomy but not by phentolamine. Restraint stress significantly delayed solid gastric emptying, which was improved by astressin2-B, guanethidine, and celiac ganglionectomy. Our research suggests that restraint stress inhibits solid gastric emptying via a central CRF type2 receptor and peripheral sympathetic neural pathway in rats.     

Effect of chronic guanethidine treatment on vascular norepinephrine content in the neonatal domestic pig

Vinblastine, 6-hydroxydopamine, and antibody to nerve growth factor have been shown to destroy sympathetic neurons in neonatal rats. High doses of guanethidine produce permanent sympathectomies in the adult or newborn rat. Similar studies in the cat, rabbit, and hamster demonstrate that the sympathetic nervous systems are not destroyed with guanethidine. To produce permanent sympathectomy in a large animal model, guanethidine was administered to neonatal pigs. As with the cat, rabbit, and hamster, the sympathetic nervous system in the piglets was not destroyed by guanethidine.     

Guanethidine and Pupillary Reaction

Local application of guanethidine to the eye results in miosis. The sympathicolytic action of guanethidine on the pupil was proved by the consistent appearance of a Horner''s syndrome after instillation of a 10% solution into the conjunctival sac. Lack of cocaine mydriasis and unimpaired adrenaline mydriasis after guanethidine application are further evidence of this mode of action. Guanethidine is the first drug that can be consistently relied upon to produce miosis by inhibiting sympathetic impulses to the intraocular pupillary muscles; it also inhibits sympathetic impulses to Horner''s muscle of the upper lid. It is a reliable sympathicolytic agent for testing the reaction of abnormal pupils.     

Effects of alfa-receptor and adrenergic neuron blockade on indomethacin-induced changes of renal haemodynamics

The effect of prostaglandin synthesis inhibitor indomethacin was studied on renal haemodynamics by radioactive microspheres in untreated control dogs and in animals treated by the alfa-adrenergic receptor blocking agent phentolamine or by the adrenergic neuron blocking agent guanethidine. RBF was reduced by indomethacin. The reduction of blood flow was more pronounced in the inner cortical zones, which resulted in a blood flow redistribution towards the superficial cortical regions. Urine flow, osmotic concentration and electrolyte excretion did not change significantly. Pretreatment by phentolamine or by guanethidine did not influence the effect of indomethacin on renal haemodynamics or renal function. These data suggest that the sympathetic nervous system is not involved in the renal effects of indomethacin.     

Dependence of the cytotoxic effect of guanethidine on the degree of sympathetic activity

Young rats aged 15-29 days received a subcutaneous injection of guanethidine sulphate (5 mg/kg body weight) every day. Owing to damage to the postganglionic sympathetic neurones, on about the 60th day of life we observed a significant decrease in the noradrenaline concentration in these animals' hearts compared with the controls. If every guanethidine injection was followed immediately by intensive physical exercise, there was no drop in the heart noradrenaline concentration. Physical exercise of the same intensity performed a few hours before injecting guanethidine did not prevent the drop in the noradrenaline concentration in the heart. The results show that an exercise-induced increase in sympathetic activity, at a time when guanethidine is circulating in the blood and accumulating in the adrenergic neurones, inhibits the cytotoxic effect of guanethidine. Isolated physical exercise performed between the 15th and 29th day of life leads to an increase in the noradrenaline content of the heart of rats aged 60 days.     

Characteristics of the compensatory repair processes in the thyroid of 1-month-old rats as affected by sympathectomy

A considerable decrease in the amount of sympathetic nervous cells in neonatal rats injected guanethidine resulted in the depression of thyroid gland functional activity in 1-month-old animals, there was an apparent parallel increase in the proliferative activity of the gland. A 2/3 thyroidectomy led to the functional tension of the remaining part of the organ. A comparison of compensatory-reparative processes after thyroidectomy has shown similarity of reparative changes in experimental and control rats, however, the degree of repair potential was much higher in the sympathectomized thyroid gland.     

Effect of tyramine and guanethidine on dopamine-β-hydroxylase activity and norepinephrine concentrations in vesicular fraction of the heart and plasma of rats

Repeated administration of high doses of tyramine to rats results in a striking increase in plasma levels of norepinephrine (NE) and a marked depletion in tissue content of NE. The drug also may produces a moderate increase in plasma levels of dopamine-β-hydroxylase (DBH) and a decrease in DBH in synaptic vesicles of sympathetic nerves in the heart. The latter effects are prevented by a ganglionic blocking agent, indicating that they may be mediated by neuronal activation secondary to the stress attending the drug administration. Chronic administration of guanethidine, which is reported to destroy most sympathetic nerves produces more marked decrease in plasma NE levels and plasma DBH activity. The possible sources of this activity are discussed.     

Differential plasma catecholamine and neuropeptide Y responses to acute stress in rats

Neuropeptide Y (NPY) is a vasoconstrictor present in the sympatho-adrenomedullary system and may be co-released with norepinephrine (NE) and epinephrine (EPI) during sympathetic activation. We studied plasma NPY-immunoreactivity (-ir, radioimmunoassay) and catecholamine (radioenzymatic) responses during two acute stress paradigms that differ in character, intensity, and duration. The intermittent stress of footshock (0.75 and 1.5 mA, 0.5 sec duration, at 5-sec intervals, for 5 min) evoked intensity-dependent immediate increments in plasma NE and EPI, and a delayed NPY-ir response (+0.6 +/- 0.1 pmol/ml). Prolonged (60 min) immobilization caused greater increases in plasma NE and EPI levels and no changes in plasma NPY-ir until the end of the stress session (+0.3 +/- 0.1 pmol/ml). Plasma NPY-ir responses correlated with those of NE but not with EPI suggesting a sympathetic origin for the release of the peptide. Relatively greater NPY-ir responses to footshock than to immobilization may be consistent with a preferential release of the peptide by a bursting but not continuous mode of sympathetic activation. However, it may also be due to a differential activation of the sympathetic nerves and adrenal medulla by these two stress situations.     

Role of catecholamines in the inhibitory effect of immobilization stress on testosterone secretion in rats

Immobilization stress applied for 6 h induced, in adult male rats, a rise of epinephrine (E) and norepinephrine (NE) plasma levels and a decrease of baseline plasma testosterone (T) values and of human chorionic gonadotropin (hCG)-induced T response. Treatment of the animals for 5 weeks with guanethidine (G), a sympathetic neuron toxic agent, significantly decreased E and NE responses to stress and partly antagonized the inhibitory effects exerted by immobilization on T biosynthesis. Adrenalectomy totally suppressed circulating E and reduced the stress-induced NE increase while partly antagonizing the inhibitory effects exerted on T biosynthesis. Combined G and adrenalectomy treatments totally suppressed plasma E and NE, and completely blocked the effects of immobilization on T levels. Treatment of the animals with the alpha 1-adrenergic blocker, prazosin, and the beta 1-adrenergic blocker, metoprolol, did not modify the effects of stress on T biosynthesis. Treatment with propranolol or with butoxamine, a nonspecific beta- and a specific beta 2-adrenergic receptor blocker, respectively, antagonized the testicular hyposensitivity to hCG induced by stress. Stress- or treatment-induced changes of plasma luteinizing hormone (LH) and hCG levels were not consistently correlated with plasma T modifications. These findings suggest that at least part of the inhibitory effects of immobilization stress on T biosynthesis is exerted by catecholamines through a beta 2-adrenergic receptor.     

Mechanism of effect of sympathetic nervous system on skin receptors

While researching the mechanism underlying the effect of the sympathetic nervous system on the operation of skin receptors, we demonstrated that a tremendous role in this process is played by smooth muscles, whose condition also mediates the sympathetic effect on receptors. The increase in the activity of the sympathetic nerve fibers results in an increase in the tonus of the smooth muscles which in turn alters the mechanical condition of the tissues surrounding the receptors. It was established that the change in the tonus of the smooth muscles in the skin itself affects the reaction of the receptors that is evoked by mechanical stimulation. The change in the tonus of the smooth muscles of the vessels affects the response of receptors caused by cooling of the skin.Nizhegorod Medical Institute, Russian Federation Ministry of Health. Translated from Neirofiziologiya, Vol. 24, No. 5, pp. 552–558, September–October, 1992.     

Frequency distribution of coping strategies in four populations of brown trout (Salmo trutta)

In a challenging situation some animals respond by active avoidance, aggression and an activation of the sympathetic nervous system whereas others respond by immobility, low levels of aggression and a predominant adrenocortical stress response. When consistent over time and across situations such inter-individual differences in behavioural and physiological stress responses are referred to as stress coping strategies. In a previous study we reported the existence of two distinct stress coping strategies in a sea-ranched brown trout (Salmo trutta) population. Using the same method, we here show that four brown trout populations with different origin, but reared under identical conditions, differ in their endocrine stress response, behaviour during hypoxia and aggression. Further more, if individuals are classified as high- and low responsive based on post-stress blood plasma noradrenalin levels (indicator of sympathetic reactivity) the frequency distribution shows that populations with hatchery origin are biased towards having higher frequencies of high responsive individuals. However, the number of high responsive trout ranges from 14-48% in the different populations which shows that generally the frequency is biased towards lower levels of high responsive individuals. We discuss different frequency-dependent mechanisms that maintain multiple phenotypes in populations and speculate about differences in selection regime among the studied populations.     

The effect of laser puncture on the functional indices of the mammalian body

Biologically active points (acupuncture points) and reflexogenic zones of Wistar rats of different age were exposed to He-Ne laser radiation with the subsequent control of acetylcholine esterase activity, electric parameters of skeletal muscles and heart, and physical activity. Laser puncture was shown to increase the sympathetic nervous system tonus which was manifested by the decreased acetylcholine esterase activity and increased heart rate. Laser puncture stimulated the growth of membrane potential and increased considerably the performance capability of animals, particularly of three-month-olds.