Influences of temperature change on the relaxation and amplitude inhibition by noradrenaline in the rabbit jejunum

Summary In the rabbit jejunum, the elevation of temperature within the range of 25–37°C diminished the sensitivity to noradrenaline (NA) for both the relaxation and amplitude inhibition. The relaxation by NA was mainly mediated via adrenergic -receptors at 25, 30 or 37°C. The amplitude inhibition was mediated via -receptors at 37°C, and both - and -receptors at 30 or 25°C.     

Effects of temperature on the responses to noradrenaline, isoprenaline and histamine on isolated rabbit mesenteric artery.

On the rabbit mesenteric artery, the elevation of temperature from 25 degrees up to 42 degrees diminished the affinity of histamine, whereas that of noradrenaline to the alpha-adrenoceptors remained unchanged. The presence of beta-adrenoceptors could not be demonstrated.     

Endothelium-dependent relaxation induced by sodium fluoride in the rabbit ear artery

Summary Sodium fluoride (NaF) produced concentration-dependent relaxation of isolated rabbit ear artery precontracted with norepinephrine. In contrast, an arterial preparation with the endothelium rubbed off did not relax, but contracted in response to NaF. NaF-induced relaxation was not influenced by indomethacin but was inhibited by methylene blue or N^G-monomethyl-L-arginine. The results indicate that NaF relaxes the artery by releasing a so-called EDRF.     

Endothelium-dependent relaxation induced by sodium fluoride in the rabbit ear artery

Sodium fluoride (NaF) produced concentration-dependent relaxation of isolated rabbit ear artery precontracted with norepinephrine. In contrast, an arterial preparation with the endothelium rubbed off did not relax, but contracted in response to NaF. NaF-induced relaxation was not influenced by indomethacin but was inhibited by methylene blue or NG-monomethyl-L-arginine. The results indicate that NaF relaxes the artery by releasing a so-called EDRF.     

Effects of alpha- and beta-adrenergic blockers on the actions of noradrenaline on body temperature in the newborn guinea-pig.

The effect of NA injected into the lateral cerebral ventricle on Tc was blocked by alpha-adrenergic receptor blockers, but not by beta-receptor blockers, whereas the effect of systemically administered NA was blocked by i.p. administered beta-receptor blockers, but not by alpha-blockers.     

Structure-activity relationship of various ephedrine isomers on noradrenaline uptake by the isolated perfused rabbit heart]

(-)Ephedrine, (+) Ephedrine, (-) psi ephedrine and (+) psi ephedrine inhibit both the neuronal and extraneuronal uptakes of noradrenaline in isolated Rabbit heart. (-) ephedrine is the most active isomer for the inhibition of both neuronal and extraneuronal uptakes. The relative inhibition potential of the three other isomers is not the same when applied to one or other uptake.     

Ouabain action on sodium,chloride and fluid transport in rabbit jejunum and ileum

Riassunto É stato studiato l'effetto della ouabaina sul trasporto di Na, Cl e fluido in digiuno e ileo isolato di coniglio. Mentre in entrambi i tratti intestinali il flusso mucosa-serosa di Na è inibito dal glicoside, il flusso nello stesso senso di Cl, di cui è stata dimostrata una componente attiva, non viene modificato. Poichè inoltre il trasporto di fluido viene inibito dalla ouabaina in misura diversa in digiuno e in ileo, si suggerisce la presenza di sistemi ATPasici non ouabaino-sensibili accanto alla Na–K ATPasi sensibile alla ouabaina che si ammette essere responsabile del trasporto di Na.

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Experiments not reported in this paper show that ouabain 5×10^–4 M does not enhance the ileal Na influx inhibition and also does not modify the Cl influx. Moreover ouabain 10^–4 M affects jejunal Na influx to a less significant extent than 5×10^–4 M.     

Effects of alpha- and beta-adrenergic blockers on the actions of noradrenaline on body temperature in the newborn guinea-pig

Summary The effect of NA injected into the lateral cerebral ventricle on T_c was blocked by alpha-adrenergic receptor blockers, but not by beta-receptor blockers, whereas the effect of systemically administered NA was blocked by i.p. administered beta-receptor blockers, but not by alpha-blockers.Acknowledgments. The author is indebted to Ciba-Geigy Ltd for generous gift of phentolamine, and to Imperial Chemical Industries Ltd, for supplying propranolol and practolol.     

Biochemical evidence for two types of noradrenaline storage particles in rabbit iris

Summary Centrifugation techniques were used to determine the subcellular distribution of noradrenaline (NA) and dopamine -hydroxylase (DH) in the rabbit iris. By application of isopycnic and differential gradient centrifugation methods 2 types of NA vesicles could be demonstrated. Of the total particle bound NA about 70% is associated with light and about 30% with heavy vesicles. For both types of vesicles the distribution of DH reflected that of NA.     

Central effects of 5-hydroxytryptamine and noradrenaline on body temperature and oxygen consumption in infant rats

Zusammenfassung Injektionen von 5-Hydroxytryptamin und Noradrenalin in die Gehirnventrikel junger Ratten verursachen einen verminderten Sauerstoffverbrauch und eine Hypothermie bereits am ersten Tag nach der Geburt Effekte, die mit dem Alter verstärkt, auftreten.     

Dissociation between inhibition of phospholipid methylation and production of PAF-acether by rabbit platelets

Summary Platelet-activating-factor (PAF-acether, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) is formed by and released from rabbit platelets stimulated with thrombin, with the ionophore A23187, with collagen and with the platelet-stimulating glycoprotein convulxin. We here show that 3-deazaadenosine (C₃ado) and L-homocysteine (HCy), two inhibitors of platelet methylation, reduced the formation of PAF-acether and of its deacetylated product lyso-PAF-acether by rabbit platelets challenged with thrombin, under conditions where the accompanying aggregation was not significantly modified. In contrast, platelet aggregation induced by convulxin was completely and irreversibly blocked when C₃ado and HCy were associated. Aggregation by thrombin was not affected by the methylation inhibitors even when ADP was scavenged and rhromboxane formation was suppressed. Our results indicate that phospholipid methylation, thrombin-induced platelet aggregation and formation of PAF-acether can be dissociated. The formation of PAF-acether by rabbit platelets can be blocked by mechanisms other than inhibition of phospholipase A2, since the latter is not affected by C₃ado and/or HCy.     

Dissociation between inhibition of phospholipid methylation and production of PAF-acether by rabbit platelets

Platelet-activating-factor (PAF-acether, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) is formed by and released from rabbit platelets stimulated with thrombin, with the ionophore A23187, with collagen and with the platelet-stimulating glycoprotein convulxin. We here show that 3-deazaadenosine (C3ado) and L-homocysteine (HCy), two inhibitors of platelet methylation, reduced the formation of PAF-acether and of its deacetylated product lyso-PAF-acether by rabbit platelets challenged with thrombin, under conditions where the accompanying aggregation was not significantly modified. In contrast, platelet aggregation induced by convulxin was completely and irreversibly blocked when C3ado and HCy were associated. Aggregation by thrombin was not affected by the methylation inhibitors even when ADP was scavenged and thromboxane formation was suppressed. Our results indicate that phospholipid methylation, thrombin-induced platelet aggregation and formation of PAF-acether can be dissociated. The formation of PAF-acether by rabbit platelets can be blocked by mechanisms other than inhibition of phospholipase A2, since the latter is not affected by C3ado and/or HCy.     

Elevated left ventricular stiffness by noradrenaline in myocardial ischaemia.

Infusion of noradrenaline (1.0 mug/kg/min body weight, i.v.) brings about an increase of the diastolic wall stiffness in the ischaemic canine heart. Similar effect is not elicitable in the normal heart.     

Differential sensitivity of pinna reflex and esophageal temperature to clonidine in mice depleted of central noradrenaline by DSP-4

Mice injected with DSP-4 [N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine], a selective noradrenergic neurotoxin, had marked depletions of central noradrenaline and an attenuated post-decapitation reflex. DSP-4-treated mice exhibited an increased sensitivity to the alpha 2-adrenoceptor agonist clonidine as measured by inhibition of the pinna reflex, but normal sensitivity as measured by hypothermia. This differential sensitivity may reflect the presence of supersensitive postsynaptic alpha 2-adrenoceptors in some, but not all, CNS regions after DSP-4 treatment.