Tonus

Even if K is temperature dependent, the ooexistenoe ourve oan still be defined m tonus of a reduoed temperature = 2RT/K(T), although the reduoed temperature is then no longer direotly proportional to the temperature T. 

Landman R, Descamps D, Peytavin G, Trylesinski A, Katlama C, Girard PM, Bonnet B, Yeni P, Bentata M, Michelet C, Benalycherif A, Brun VF, Miller MD, Flandre P (2005) Early virologic failure and rescue therapy of tenofovir, abacavir, and lamivudine for initial treatment of HlV-1 infection TONUS study, HIV Clin Trials 6 291-301... 

Bonnard E., Mazarguil H., Zajac J.M. Peptide nucleic acids targeted to the mouse proNPFF(A) reveal an endogenous opioid tonus. Peptides 2002 23 1107-1113. 

Acute physiological responses to opiate administration occur rapidly and include constricted pupils, decreased pulse rate, reduced body temperature, slowed respiration rate and impaired reflexes. In addition, there is a marked slowing of the digestive system through an altering of the tonus and motility of the stomach and intestines, allowing for greater water absorption. This last effect is not subject to tolerance, and constipation is a common side effect even for chronic users. Indeed, some report that this is the worst side effect of opiate use. 

Major effector proteins for G-pro-tein-coupled receptors include adenylate cyclase (ATP intracellular messenger cAMP), phospholipase C (phos-phatidylinositol intracellular messengers inositol trisphosphate and di-acylglycerol), as well as ion channel proteins. Numerous cell functions are regulated by cellular cAMP concentration, because cAMP enhances activity of protein kinase A, which catalyzes the transfer of phosphate groups onto functional proteins. Elevation of cAMP levels inter alia leads to relaxation of smooth muscle tonus and enhanced contractility of cardiac muscle, as well as increased glycogenolysis and lipolysis (p. 

Because digestion of food in the intestinal tract is dispensable and only counterproductive, the propulsion of intestinal contents is slowed to the extent that peristalsis diminishes and sphinc-teric tonus increases. However, in order to increase nutrient supply to heart and musculature, glucose from the liver and free fatty acid from adipose tissue must be released into the blood. The bronchi are dilated, enabling tidal volume and alveolar oxygen uptake to be increased. 

Smooth muscle effects. The opposing effects on smooth muscle (A) of a-and p-adrenoceptor activation are due to differences in signal transduction (p. 66). This is exemplified by vascular smooth muscle (A). ai-Receptor stimulation leads to intracellular release of Ca + via activation of the inositol tris-phosphate (IP3) pathway. In concert with the protein calmodulin, Ca + can activate myosin kinase, leading to a rise in tonus via phosphorylation of the contractile protein myosin. cAMP inhibits activation of myosin kinase. Via the former effector pathway, stimulation of a-receptors results in vasoconstriction via the latter, P2-receptors mediate vasodilation, particularly in skeletal muscle - an effect that has little therapeutic use. 

In benign hyperplasia of the prostate, a-blockers (terazosin, alfuzosin) may serve to lower tonus of smooth musculature in the prostatic region and thereby facilitate micturition (p. 252). 

Responses to activation of the parasympathetic system. Parasympathetic nerves regulate processes connected with energy assimilation (food intake, digestion, absorption) and storage. These processes operate when the body is at rest, allowing a decreased tidal volume (increased bronchomotor tone) and decreased cardiac activity. Secretion of saliva and intestinal fluids promotes the digestion of foodstuffs transport of intestinal contents is speeded up because of enhanced peristaltic activity and lowered tone of sphincteric muscles. To empty the urinary bladder (micturition), wall tension is increased by detrusor activation with a concurrent relaxation of sphincter tonus. 

In blood vessels, the relaxant action of ACh on muscle tone is indirect, because it involves stimulation of M3-cho-linoceptors on endothelial cells that respond by liberating NO (= endothelium-derived relaxing factor). The latter diffuses into the subjacent smooth musculature, where it causes a relaxation of active tonus (p. 121). 

Lowering of pupillary sphincter tonus and pupillary dilation by local administration of homatropine or tropic-amide (mydriatics) allows observation of the ocular fundus. For diagnostic uses, only short-term pupillary dilation is needed. The effect of both agents subsides quickly in comparison with that of atropine (duration of several days). 

Mechanisms of action. The tonus of vascular smooth muscle can be decreased by various means. ACE inhibitors, antagonists at ATI-receptors and antagonists at a-adrenoceptors protect against the effects of excitatory mediators such as angiotensin 11 and norepinephrine, respectively. Prostacyclin an-Ltillmann, Color Atlas of Pharmacology 2000 Thieme All rights reserved. Usage subject to terms and conditions of license. 

In heart failure, cardiac output rises again because ventricular afterload diminishes due to a fall in peripheral resistance. Venous congestion abates as a result of (1) increased cardiac output and (2) reduction in venous return (decreased aldosterone secretion, decreased tonus of venous capacitance vessels). 

Peripheral effects concern the motility and tonus of gastrointestinai smooth muscie segmentation is enhanced, but propulsive peristalsis is inhibited. The tonus of sphincter muscles is raised markedly. In this fashion, morphine elicits the picture of spastic constipation. The antidiarrheic effect is used therapeutically (ioperamide, p. 

Clonazepam is used in somnambulic epilepsy, various forms of muscular tonus, insomnia (especially in patients with structural brain lesions), and psychomotor agitation. Synonyms of this drag are clonopin and rivotril. 

Pharmacology Trospium is an antispasmodic, antimuscarinic agent. Trospium antagonizes the effect of acetylcholine on muscarinic receptors in cholinergically innervated organs. Its parasympatholytic action reduces the tonus of smooth muscle in the bladder. Trospium increases maximum cystometric bladder capacity and volume at first detrusor contraction. 

At the bronchi, predominantly /32-adrenoceptors are present on the smooth muscle cells. Therefor noradrenaline has hardly any influence on the muscular tonus whereas adrenaline induce a dilatation especially of precontracted bronchi, independent of the cause (histamine, acetylcholine, kinines, prostanoides). This effect can be used therapeutically in the therapy of bronchial asthma. In general the local application by aerosol is more useful than the systemic application, due to lesser side effects and the additional, beneficial effect of the reduction of mucosa swelling. 

The effect of catecholamines on the human uterus, which can be mediated by a- and /3-adrenoceptors, depends on its functional state. During pregnancy /32-adrenoceptor stimulation decrease the uteral tonus, an effect that can be used therapeutically. /32-Adrenoceptor agonists are in use as tocolytics. In the bladder base and the urethral sphincter a-adrenoceptors are present, mediating a contraction, whereas the /32-adrenoceptors of the bladder wall induce a relaxation of the particular smooth muscles present at these structures. Ejaculation is regulated by a-adrenoceptors. 

Since the bronchial tonus is under the relaxant influence of 62-adrenoceptor stimulation, especially unselective jS-blockers increase the respiratory resistance. In susceptible patients this might induce airway obstruction or even acute asthma. The blockade of jS2-adrenoceptors inhibits the mobilization of free fatty acids and glucose. This might result in hypoglycemia in diabetic patients. Furthermore, these patients will be not aware of the danger since most of the sympathetically mediated alerting symptoms like tachycardia are suppressed by the jS-blockers as well. jSi-Selective blockers show this type of side-effect less pronounced than unselective compounds. 

Clonidine is an agonist at a - and o 2-adreno-ceptor subtypes. It reduce the sympathetic tonus and is thereby a useful antihypertensive drug. Clonidine can induce sedation, depression and peripheral side effects like a dry mouth. Unspecific a-adrenoceptor blocking agents like tricyclic antidepressants can reduce the antihypertensice effect of clonidine. 

Methyldopa is an false substrate for the dopamine-/ -hydroxylase resulting in a-methylnor-adrenaline. This metabolite is an a2-adrenoceptor agonist an induce, like clonidine, a centrally mediated reduction of sympathetic tonus. 

Mechanism of Action A parasympathetic, anticholinesterase agent that inhibits destruction of acetylcholine by acetylcholinesterase, thus causing accumulation of acetylcholine at cholinergic synapses. Results in an increase in cholinergic responses such as miosis, increased tonus of intestinal and skeletal muscles, bronchial and ureteral constriction, bradycardia, and increased salivary and sweat gland secretions. Therapeutic Effect Diagnosis of myasthenia gravis. 

Mechanism of Action A urinary antispasmodic t hat act s as a direct antagonist at muscarinic acetylcholine receptors in cholinergically innervated organs. Reduces tonus (elastictension) of smooth muscle in the bladder and slows parasympathetic contractions. Therapeutic Effect Decreases urinary bladder contractions, increases residual urine volume, and decreases detrusor muscle pressure. 

The cases where terpene metabolism has been studied In Insects are very few Indeed. Certain Ips and Dendroctonus bark beetles convert monoterpenes such as a-plnene, 6-plnene and myr-cene to oxidation products, some of which have pheromonal activities ( 5, 3A, 35). A Dendroc tonus bark beetle s cytochrome... 

Muscie Tonus Lost, Motor Output Biocked... 

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