Inhibition of epinephrine and gonadotropic hormone induced ornithine decarboxylase activity by phenoxybenzamine in the testis of immature rat

The effect of α and β adrenergic receptor blockers on epinephrine and gonadotropic hormone induced ornithine decarboxylase (ODC) activity in the testis of immature rats was studied. Intratesticular injection with phenoxybenzamine at 15 min before treatment with epinephrine or gonadotropic hormones blocked ODC activity. Similar injection with propranolol or practolol had no effect on ODC activity. These results show that α adrenergic receptors are involved in the action of epinephrine and gonadotropic hormones in the testis.     

Characterization of the beta-adrenergic receptor mediating secretion of parathyroid hormone

In vitro incubation studies with bovine parathyroid gland slices compared the relative responsiveness of parathyroid hormone (PTH) secretion to isoprotherenol, epinephrine or norepinephrine. Isoproterenol was the most potent and norepinephrine the least potent of the three stimuli, suggesting a beta 2 type of an adrenergic response. However in this in vitro system, tazalol, a selective beta 1 adrenergic agonist significantly stimulated PTH secretion, whereas terbutaline, a selective beta 2 agonist had no effect. In addition, practolol, a selective beta 1 adrenergic antagonist blocked isoproterenol- or tazolol-stimulated PTH secretion. In vivo studies in normal human subjects showed that injection of te nonselective beta agonist, isoproterenol, (0.15 mg s.c.) significantly increased, whereas injection of the selective beta 2 agonist, terbulatine (0.3 mg s.c.) had no effect on serum PTH levels. These latter studies with putative selective beta adrenergic agents suggest that the beta adrenergic receptor mediating PTH secretion is of the beta 1 type (in contrast to the studies above with nonselective agents). The studies suggest that the beta adrenergic receptor mediating PTH secretion apparently differs from the classical beta 1 receptor described in th myocardium or the classical beta 2 receptor described in the bronchial smooth muscle.     

Central adrenoceptors and basal prolactin release in the rat

The influence of the central adrenergic system on basal prolactin secretion was investigated in the rat. Several selective adrenoceptor blockers were centrally administered and their effects on prolactin secretion were observed. Blockade of beta-1 receptors by practolol, beta-2 receptors by IPS 339 and alpha-2 receptors by DG-5128 did not modify basal prolactin secretion, but alpha-1 adrenoceptor blockade by prazosin strongly enhanced prolactin plasma levels. These findings suggest that noradrenergic pathways in the central nervous system exert inhibitory tone on basal prolactin secretion, and that this effect seems to be mediated by alpha-1 adrenoceptors.     

Positive inotropic action of insulin on piglet heart.

This study was designed to investigate changes in cardiac performance during hypoglycemia produced by the administration of insulin in the newborn piglet. With heart rate, aortic pressure, and aortic flow held constant, the treated group demonstrated a pronounced positive inotropic response manifested by an increase of dP/dt max to 138% of control values. Central nervous system function and beta adrenergic activity were excluded from the preparation by ligation of the brachiocephalic vessels and administration of practolol. For reasons discussed, it is unlikely that the findings can be ascribed to glucagon contamination. Therefore, the increase in contractility presumably resulted from a direct effect of insulin upon the myocardium. Clinical and laboratory data suggest that the resistance of the neonate to hypoxia is modified by glycogen stores. Insulin is known to increase glycogen synthesis, and this effect might be expected to augment myocardial resistance to hypoxia. Under the conditions of these experiments, however, pretreatment with insulin had no demonstrable influence on the rate of deterioration of cardiac function during hypoxia. The mechanism of cardiac stimulation by insulin is unknown but may involve calcium fluxes.     

Interaction of dextrorotatory opioids with phencyclidine recognition sites in rat brain membranes

The potencies of several dextrorotatory opioids, including four pairs of enantiomers, as inhibitors of specific [³H]PCP binding to rat brain synaptic membranes has been determined. Of the compounds tested unlabeled phencyclidine (PCP) was the most potent followed by (?)? cyclazocine > dextrorphan > (+) ketamine > (+) cyclazocine > (+)? SKF10,047 > levorphanol > dextromethorphan > (?) SKF10,047 > (?)? ketamine > (±) pentazocine and > (±) ethylketocyclazocine. The opiate mu receptor ligands, morphine, naloxone and naltrexone were virtually inactive as competitors of specific [³H]PCP binding. Unlike the stereostructural requirements for opiate mu receptors where activity resides predominantly in the levorotatory enantiomers, the present results support the contention that binding to the [³H]PCP labeled recognition site may reside in either the levorotatory or the dextrorotatory enantiomer. The specific binding of [³H]PCP which was defined as total binding minus that occurring in the presence of 10μM dextrorphan was found to be of a high affinity, saturable, reversible and sensitive to thermal degradation. These results suggest that certain dextrorotatory morphian derivatives may prove to be useful probes in further investigations of the molecular characteristics of the [³H]PCP binding site in brain membrane preparations.     

Interaction of alpha adrenergic antagonists with calmodulin

Several alpha-adrenergic antagonists inhibited the activation of calmodulin-stimulated phosphodiesterase at concentrations that had little or no effect on basal phosphodiesterase activity. The most potent of these compounds were phenoxybenzamine and dibenamine (IC50 values of about 1 microM); the amino acid ergot alkaloids ergocryptine, ergocristine, ergotamine and their dihydrogenated derivatives were less potent calmodulin-inhibitors (IC50 values of 35-80 microM). The amino ergot alkaloids ergonovine and methysergide were essentially devoid of inhibitory activity. A variety of other alpha 1-antagonists (phentolamine, tolazoline and prazosin), an alpha 2-antagonist (yohimbine), alpha-agonists (norepinephrine, phenylephrine and clonidine), beta-adrenergic antagonists (propranolol and practolol) and the beta-adrenergic agonist methoxyphenamine displayed little or no anti-calmodulin activity (IC50 values greater than 300 microM). Similarly, the alkylating agents chlorambucil and mechlorethamine also failed to inhibit calmodulin activity. Phenoxybenzamine and dibenamine inhibited calmodulin activity irreversibly, whereas the inhibition caused by other alpha adrenergic blocking agents was reversible. Phenoxybenzamine inhibited calmodulin activity by binding directly to it. This binding was calcium-dependent and irreversible. The irreversible binding and inhibition of calmodulin activity by phenoxybenzamine (or dibenamine) may serve as a useful tool for studying the sites at which drugs bind to calmodulin and may also be useful for studying the distribution and turnover of calmodulin.     

Mechanism of action of βadrenergic receptor blocking agents in angina pectoris: Comparison of action of propranolol with dexpropranolol and practolol

The effect on exercise tolerance of racemic propranolol has been assessed in eight angina pectoris patients and compared with that of dexpropranolol (the dextro isomer of propranolol), practolol (I.C.I. 50172), and saline. Dexpropranolol has the same local anaesthetic action as propranolol with negligible β-adrenergic receptor blocking activity, while practolol is a cardio-selective β-adrenergic blocking agent which does not have local anaesthetic activity.Saline and dexpropranolol had no significant effect on exercise time; racemic propranolol and practolol improved exercise tolerance in six subjects, the response to the two drugs being very similar in individual patients. It was concluded that the beneficial effect of propranolol in angina pectoris results from its action as a β-adrenergic receptor blocking agent and is not due to its local anaesthetic, or quinidine-like, activity.     

Beta1 and beta2 receptor mechanisms in rat jugular veins: differences between norepinephrine and isoproterenol-induced relaxation.

The rat jugular vein possesses both beta₁ and beta₂ adrenergic receptors based on the use of two beta₁ antagonists, practolol and atenolol and two beta₂ antagonists, butoxamine and N-isopropylmethoxamine. In this vessel, norepinephrine and nylidrin interact primarily with beta₁ receptors whereas isoproterenol and salbutamol interact with both beta₁ and beta₂ receptors showing a slight preference for beta₂ receptors. Isoxsuprine-induced relaxation was not blocked by either beta₁ or beta₂ antagonists. Selectivity of norepinephrine for beta₁ receptors and of isoproterenol for beta₂ receptors also occurred in circular preparations of the portal vein after alpha adrenergic blockade. However, after alpha adrenergic blockade in rat aorta, practolol and N-isopropylmethoxamine were equieffective as antagonists of relaxation to norepinephrine and isoproterenol although N-isopropylmethoxamine was somewhat more effective than practolol.     

Catecholamine and guanine nucleotide activation of skeletal muscle adenylate cyclase.

Activation of adenylate cyclase by guanine nucleotide and catecholamines was examined in plasma membranes prepared from rabbit skeletal muscle. The GTP analog, 5'-guanylyl imidodiphosphate caused a time and temperature-dependent activation of the enzyme which was persistent, the Ka was 0.05 microM. 5'-Guanylyl imidodiphosphate binding to the membranes was time and temperature dependent, KD 0.07 microM. Beta adrenergic amines accelerated the rate of 5'-guanylyl imidodiphosphate activation of the enzyme with an order of potency isoproterenol approximately soterenol approximately salbutamol greater than epinephrine greater than norephrine. Catecholamine activation was antagonized by propranolol and the beta2 antagonist butoxamine; the beta1 antagonist practolol was inactive. [3H]Dihydroalprenolol bound to the membranes and binding was antagonized by beta adrenergic agonists with an order of potency similar to the activation of adenylate cyclase and was antagonized by butoxamine but not by practolol. The data are consistent with the idea that adenylate cyclase in skeletal muscle plasma membranes is coupled to adrenergic receptors of the beta2 type.     

Evidence for alpha-1 adrenergic receptor regulation of atriopeptin release from the isolated rat heart

Atrial myocardium is the source of a recently described peptide hormone termed atriopeptin. Atriopeptin is thought to have a role in the regulation of systemic arterial pressure, fluid balance and plasma electrolyte homeostasis. Isolated rat hearts release atriopeptin into the coronary effluent, and we have found that this release is stimulated by the administration of norepinephrine, a compound with alpha and beta adrenergic properties. Infusion of the pure beta-receptor agonist, isoproterenol, failed to stimulate the release; however, the alpha-1 receptor agonist phenylephrine induced the release in a dose-dependent manner. The stimulation of atriopeptin release by norepinephrine and phenylephrine was inhibited by alpha-blockade with phentolamine. Administration of BHT-920, a selective alpha-2 agonist, had no effect on atriopeptin release. We conclude that atriopeptin secretion by the atrial myocyte is stimulated by activation of the alpha-1 adrenergic receptor. This finding suggests an involvement of the sympathetic nervous system in the physiologic regulation of the secretion of this hormone.     

MODULATION OF INTERFERON γ INDUCED INCREASES IN CATHEPSIN B IN THP-1 CELLS BY ADRENERGIC AGONISTS AND ANTAGONISTS

In order to investigate the possible modulation of macrophage function by the autonomic nervous system, the effect of adrenergic agonists and antagonists on interferon (IFN)-γ-induced increases in cathepsin B (CB) in a macrophage-like cell line was studied. It has been shown previously that IFN-γ induces increased CB activity in phorbol myristate acetate (PMA)-primed THP-1 cells. Isoproterenol (ISO) (10μm ), a mixed β-receptor agonist, increased the induction of CB activity in the cells but norepinephrine (10μm ) and epinephrine (10μm ), the α and β receptor agonists, had little effect. The addition of the mixed α-receptor antagonist phentolamine (10μm ) had no effect on ISO induced increases but the mixed β-receptor antagonist propranolol (10μm ) and the selective β₁-receptor antagonist atenolol produced significant inhibition. These results suggest that the activation of β-receptors could be involved in the induction of CB activity in macrophages and provide a possible mechanism for the regulation of macrophage effector function by the autonomic nervous system. Dibutyryl cAMP (1mm ) alone also induced increases in CB in THP-1 cells, and H-89 or HA1004 abrogated the effect of dibutyryl cAMP, suggesting that the effect of ISO on CB could be through the elevation of cAMP and the activation of cAMP-dependent protein kinases.     

Vasodilator responses to ATP and UTP are not dependent on nitric oxide release, K+(ATP) channel activation, or the release of vasodilator prostaglandins in the hindlimb vascular bed of the cat

The effects of the purinergic agonists, ATP, ATPgammaS, UTP, and 2-Met-Thio AP, were investigated in the hindlimb vascular bed of the cat. Under constant-flow conditions, injections of the purinergic agonists into the perfusion circuit elicited dose-related decreases in perfusion pressure. The order of potency was 2-Met-Thio ATP > ATPgammaS > ATP > UTP. In contrast, injections of GTPgammaS, cAMP, UDP, and UMP had no effect. Vasodilator responses to ATP, ATPgammaS, UTP, and 2-Met-Thio ATP were increased in duration by the cAMP phosphodiesterase inhibitor rolipram, whereas the cGMP phosphodiesterase inhibitor zaprinast had no effect. Responses to the purinergic agonists were not altered by nitric oxide synthase inhibitors, K+(ATP) channel antagonists, cyclooxygenase inhibitors, or agents that interfere with the actions of the adrenergic nervous system. These data suggest that ATP, ATPgammaS, UTP, and 2-Met-Thio ATP dilate the hindlimb vascular bed by a direct cAMP-dependent mechanism, and that the release of nitric oxide, vasodilator prostaglandins, K+(ATP) channel opening, or an inhibitory effect on the adrenergic nervous system play little, if any, role in mediating or modulating responses to the purinergic agonists in the hindlimb circulation of the cat.     

Possible role of antibody specific for a practolol metabolite in the pathogenesis of oculomucocutaneous syndrome.

The clinical distribution of an antibody to a metabolite of practolol was investigated, particularly in relation to the oculomucocutaneous syndrome. Serum samples were obtained from patients with and without a history of adverse reaction to practolol and two groups of control patients who had never taken the drug. Five patients also participated in a challenge study. The presence of the antibody was found to be related to practolol administration, and antibody activity could be increased by antigenic challenge. The role of this antibody in the pathogenesis of the oculomucocutaneous syndrome remains uncertain. The lesions may be the result of a hitherto unknown type of hypersensitivity response to practolol.     

Vegetative nervous system's contribution to the development of stress induced gastric ulcers]

A vegetative nervous system contribution to the development of stress-induced gastric ulcers has been investigated. The experiments involved male Wistar rats. Vegetative nervous system activity has been assessed with acetylcholine brain and stomach tissue levels and synthesis as well as adrenaline and noradrenaline levels in adrenals and gastric wall. The results have shown, that ulcerogenic effect of stress is accompanied by the increase in both cholinergic and adrenergic activities. Moreover, it has been shown, that markedly strong stimulation of the adrenergic system in some rats, together with pharmacologic activation of alpha-adrenergic receptors, inhibits the development of stress-induced gastric ulcers.     

Alpha and beta adrenergic control of contraction force of perch heart (Perca fluviatilis) in vitro

Noradrenaline showed a negative inotropic effect on the isolated electrically triggered atrium of the perch. The effect was stronger at lower temperature and was antagonized by an alpha adrenergic blocker, phentolamine. The inotropic effect of adrenaline was dependent on incubation temperature. The effect was negative at 15 C but biphasic at 24 C, where with increasing adrenaline concentration a positive inotropic effect was followed by negative inotropy. Phentolamine not only antagonized the negative inotropic effect of adrenaline at 15 degrees C but changed it to positive. This positive inotropic effect was antagonized by a beta adrenergic blocker, propranolol. On the triggered ventricular strip adrenaline had no effect at 6 or 15 C, but increased contraction force at 24 C. It can be suggested that in the perch heart atrium there is an activity balance of alpha and beta receptors, which mediate the negative and positive inotropic control, respectively. As in higher vertebrates, alpha adrenergic activation decreases and beta activation increases by agonists in the following order: noradrenaline, adrenaline and isoprenaline. The balance changes towards increased beta activity when temperature rises.     

Modulation of in situ murine neuroblastoma tumor growth by the adrenergic nervous system: differential response of clonal cell lines to chemical sympathectomy

The in situ growth characteristics of C-1300, N1E-115 and NS20Y murine neuroblastoma (MNB) tumor cell lines were compared in normal and sympathectomized A/J mice. Adrenergic nerve ablation was produced in neonatal mice by administration of 6-hydroxydopamine (6-OHDA) at a dose of 100 micrograms/gm body weight on post-natal days 4, 6, 8 and 10; controls received equivalent volumes of the vehicle solution (0.9% NaCl/0.1% Ascorbic Acid). All mice were inoculated subcutaneously with 10(6) viable MNB cells four to six weeks after treatment with 6-OHDA or vehicle. The growth rates of tumors produced by the adrenergic MNB cell lines, C-1300 and N1E-115, were significantly lower in sympathectomized mice when compared to control animals. In contrast, tumors induced by the cholinergic MNB cell line, NS20Y, grew at similar rates in both sympathectomized and control mice. All tumors obtained from control and sympathectomized mice regardless of whether they derived from cell lines characterized as cholinergic (NS20Y) or adrenergic (C-1300, N1E-115), contained both norepinephrine and dopamine. Depletion of adrenergic neurotransmitter in A/J mice was induced by administration of reserpine (5-10 micrograms/kg/day) beginning 30 days prior to implantation of the C-1300 MNB cell line and continuing until sacrifice of the animal. The effect of this treatment on organ and tumor catecholamine concentrations was confirmed by high-pressure liquid chromatography. Splenic catecholamine levels in reserpine-treated animals were reduced to 20% of controls as compared to 9% in the neonatally-sympathectomized group. However, there was no discernible effect on C-1300 MNB tumor growth in the reserpine-treated animals. C-1300 MNB tumor concentrations of nor-epinephrine and dopamine were significantly lower in the reserpine-treated animals than in controls. The suppression of tumor growth by adrenergic nerve ablation is selective for specific MNB tumor cell lines. An anatomically intact sympathetic nervous system appears to exert a greater influence than competency of adrenergic neuro-humoral transmission on MNB tumor growth. These data support the hypothesis that modulation of MNB tumor growth by the adrenergic nervous system is not mediated via catecholamines but may be modulated by endogenous growth factor(s).     

Interaction of alpha and beta adrenergic stimulation on aortic ornithine decarboxylase activity

The interaction between beta and alpha adrenergic agonists on regulation of cockerel aortic ornithine decarboxylase (ODC) activity was examined. The beta adrenergic agonist isoproterenol both reduced basal aortic ODC activity and prevented induction of the decarboxylase by the alpha adrenergic agonist methoxamine. 3-Isobutyl-1- methylxanthine (IBMX) similarly reduced basal ODC activity and blocked induction of the enzyme by methoxamine. When given ten minutes before or after methoxamine, isoproterenol prevented aortic ODC induction, but not large sustained increases in blood pressure evoked by the alpha adrenergic agonist. In contrast, when injected three hours after methoxamine, isoproterenol had no effect on already elevated levels of enzyme activity. Addition of isoproterenol (10(-7)M), IBMX (1 mM) or dibutyryl cAMP (2.5 mM) to isolated aortic segments cultured in minimal salts-glucose media evoked decreases in basal levels of ODC activity resembling those observed in the intact animal. These results suggest that the balance between alpha and beta adrenergic stimulation may be an important feature of the regulation of polyamine biosynthesis in artery wall cells.     

Double-blind comparison of tolamolol,propranolol, practolol,and placebo in the treatment of angina pectoris.

Forty-two patients with angina pectoris have completed a randomized, double-blind trial comparing tolamolol 100 mg and 200 mg with propranolol 80 mg, practolol 100 mg, and placebo, all given three times a day. Tolamolol 200 mg thrice daily was found to be equivalent to propranolol 80 mg thrice daily in anti-anginal efficacy. Anginal attack rates and trinitrin consumption were significantly reduced by all active treatments as compared with the placebo but tolamolol and propranolol were the most effective. Tolamolol 200 mg thrice daily was most effective in reducing blood pressure, while propranolol was most effective in reducing the resting heart rate. All treatments except the placebo significantly increased the amount of exercise which could be performed before angina appeared (exercise work), while tolamolol 200 mg thrice daily significantly reduced Robinson''s index when compared with all other active agents. The degree of S-T segment depression induced by exercise was significantly lessened by both tolamolol and propranolol but not by practolol or placebo. There was no difference in patient preference between tolamolol and propranolol but tolamolol at both dose levels was preferred to practolol. Both tolamolol and propranolol are potent adrenergic beta-receptor antagonists and equal in anti-anginal efficacy but tolamolol has the advantage of being cardioselective. It is superior to practolol.     

Adrenergic innervation of the myocardium and skeletal musculature of the rabbit exposed to vibration

Innervation of the myocardium and that of foreleg musculature has been studied in rabbits subjected to the local vibration effect. The point where the vibration is applied is the foreleg, because its nerve plexuses are in the tightest way connected with the cardiac nervous apparatus. For treatment of the sections incubation in 2% solution of glyoxylic acid is used, which is followed with luminescent microscopy. While studying adrenergic nerve plexuses of the right auricle, their luminescent activity is stated to decrease more than by a half. In the ventricles only single perivascular adrenergic nerve plexuses remain. A constant reaction of the plexuses mentioned is revealed not only in the right, but in the left extremity subjected to a direct vibration. Taking into account that the vibrational effect is performed as a generalized action and it embraces the whole skeleton of the animal, it is possible to suggest that the activity of the sympathetic nervous plexuses results in a constant influence of noradrenaline on the wall of blood vessels producing their steady spasmodicity.     

Mechanisms of the antinociceptive action of (?) Epicatechin obtained from the hydroalcoholic fraction of Combretum leprosum Mart & Eic in rodents

ABSTRACT: BACKGROUND: The mechanisms of the antinociceptive activity of () epicatechin (EPI), a compound isolated from the hydroalcoholic fraction of Combreum leprosum Mart & Eicher. METHODS: were assessed in the model of chemical nociception induced by glutamate (20 mumol/paw). To evaluate the mechanisms involved, the animals , male Swiss mice (25-30 g), received EPI (50 mg/kg p.o.) after pretreatment with naloxone (2 mg/kg s.c. opioid antagonist), glibenclamide (2 mg/kg s.c. antagonist K + channels sensitive to ATP), ketanserin (0.3 mg/kg s.c. antagonist of receptor 5-HT2A), yoimbine (0.15 mg/kg s.c. alpha2 adrenergic receptor antagonist), pindolol (1 mg/kg s.c. 5-HT1a/1b receptor antagonist), atropine (0.1 mg/kg s.c. muscarinic antagonist) and caffeine (3 mg/kg s.c. adenosine receptor antagonist), ondansetron (0.5 mg/kg s.c. for 5-HT3 receptor) and L-arginine (600 mg/kg i.p.). RESULTS: The antinociceptive effect of EPI was reversed by pretreatment with naloxone and glibenclamide, ketanserin, yoimbine, atropine and pindolol, which demonstrates the involvement of opioid receptors and potassium channels sensitive to ATP, the serotoninergic (receptor 5HT1A and 5HT2A), adrenergic (receptor alpha 2) and cholinergic (muscarinic receptor) systems in the activities that were observed. The effects of EPI, however, were not reversed by pretreatment with caffeine, L-arginine or ondansetron, which shows that there is no involvement of 5HT3 receptors or the purinergic and nitrergic systems in the antinociceptive effect of EPI. In the Open Field and Rotarod test, EPI had no significant effect, which shows that there was no central nervous system depressant or muscle relaxant effect on the results. CONCLUSIONS: This study demonstrates that the antinociceptive activity of EPI in the glutamate model involves the participation of the opioid system, serotonin, adrenergic and cholinergic.