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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1 The effects of isoprenaline, propranolol and phentolamine, were studied on tritiated noradrenaline overflow elicited by postganglionic nerve stimulation in guinea-pig isolated atria. 2 Isoprenaline (1.2 times 10-minus 8M) increased while propranolol (1.0 times 10-minus 7M) reduced the overflow of tritiated noradrenaline evoked by nerve stimulation. These effects were less than those of phentolamine (3.1 times 10-minus 6M), which increased by approximately three-fold the overflow of [3H]-noradrenaline elicited by nerve stimulation. 3 Neuronal accumulation of tritiated noradrenaline in guinea-pig atria was not affected by isoprenaline, propranolol or phentolamine at the concentration employed in this study. 4 Isoprenaline (1.2 times 10-minus 8M) induced a positive chronotropic effect of about 80 percent of the maximum. On the other hand, propranolol produced a shift to the right in the frequency-response curve to nerve stimulation and in the concentration-response curve to exogenous noradrenaline in guinea-pig atria. 5 In the isolated nictitating membrane of the cat, the frequency-response curve to nerve stimulation was not modified by propranolol, while in the presence of 3.9 times 10-minus 6M of N,-2-(2,6-dimethylphenoxy)propyl-N,N,N-trimethylammonium (beta-methyl-TM 10) there was a shift to the right and a depression of slope. Neither propranolol nor beta-methyl-TM 10 affected responses to exogenous noradrenaline. 6. The effects of isoprenaline and of propranolol on transmitter release are compatible with the view that in addition to the presynaptic negative feed-back mechanism for noradrenaline release by nerve stimulation mediated via alpha-adrenoceptors a positive feed-back mechanism exists in adrenergic nerve endings which is triggered through the activation of presynaptic beta-adrenoceptors.
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PMID:Possible role of a beta-adrenoceptor in the regulation of noradrenaline release by nerve stimulation through a positive feed-back mechanism. 16 67

Isolated, superfused, field stimulated guinea-pig vas deferens, in which the noradrenaline stores had been labelled by preincubation with tritiated (-)-noradrenaline, was used to study the interaction between exogenous and endogenous acetylcholine and adrenergic neuroeffector function. Exogenous acetylcholine was found to exert a dual muscarinic effect on the preparation, consisting of depression of the secretion of tracer noradrenaline from the sympathetic nerves, as well as enhancement of the nerve stimulation-induced contraction of the preparation. The results indicate that endogenous acetylcholine may play an analogous role, since eserine enhanced the nerve stimulation-induced contraction, without markedly affecting the secretion of labelled noradrenaline (the effect was abolished by atropine), while higher concentrations of atropine depressed the contraction and actually enhanced the secretion of labelled noradrenaline. The findings support the concept that guinea-pig vas deferens has a dual, cholinergic as well as adrenergic, innervation, and that the cholinergic nerves exert a dual modulatory effect on sympathetic neuro-effector function in this tissue: Firstly they appear to restrict the secretion of sympathetic neurotransmitter (via pre-junctional muscarinic receptors, on the adrenergic nerve terminals), and secondly they seem to enhance the excitability of the smooth muscle to sympathetic neurotransmitter (via post-junctional muscarinic receptors, on the smooth muscle cells).
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PMID:Pre- and post-junctional receptor-mediated cholinergic interactions with adrenergic transmission in guinea-pig vas deferens. 16 84

Motor activity during the first 5 min in a motility meter was measured in mice given 0.025-3.2 mg/kg of the dopamine and noradrenaline receptor agonists apomorphine and clonidine, respectively. The accumulation of Dopa, as induced by the inhibitor of aromatic amino acid decarboxylase, NSD 1015, was measured in parallel in two dopamine-rich regions, i.e. the limbic system and the corpus striatum, and in two noradrenaline-rich regions, i.e. the neocortex and the lower brain stem. Low doses (0.025-0.2 mg/kg) of apomorphine reduced locomotion in a dose-dependent manner, while the reduction after higher doses was less pronounced, indicating a biphasic dose-response relationship. Clonidine caused a dose-dependent locomotor depression. When low doses of the two drugs were combined, the inhibitory effect observed was at least additive. When clonidine was combined with a high dose of apomorphine (0.8 mg/kg), it caused a significant inhibition of locomotion in a dose of 0.1-0.2 mg/kg, but not after 0.8 mg/kg, indicating a biphasic dose-response relationship. Either drug given alone reduced Dopa accumulation after inhibition of its decarboxylation, in all regions, but smaller doses of apomorphine had a clearcut effect only in the dopamine-rich regions, whereas the lowest dose of clonidine investigated (0.05 mg/kg) had an inhibitory effect on Dopa formation only in the neocortex. The relationship between the dose of apomorphine and Dopa formation in the neocortex appeared biphasic, the highest dose (3.2 mg/kg) having no significant effect. Further, apomorphine in this dose accelerated the disappearance of noradrenaline after inhibition of synthesis by alpha-methyltyrosine. Reversal of reserpine-induced suppression of motor activity was taken to indicate postsynaptic receptor activation. The threshold dose of apomorphine causing reversal was 0.2 mg/kg. The inhibitory effect of e.g. 0.05 mg/kg on locomotion and on Dopa formation suggests a preferential activation of inhibitory autoregulatory dopamine receptors by low doses of this drug. A similar trend was observed for clonidine. The basal importance of dopamine neurones for the locomotor function studied in the present paper is illustrated by the marked inhibition by low doses of apomorphine. On the other hand, the observations with clonidine suggest a somewhat less striking and perhaps less direct influence of noradrenaline neurones on motor activity. Mice with a low motor activity, as induced e.g. by reserpine or, in another experiment, mice adapted to the motility meter, displayed an increased motor activity after higher doses of apomorphine (from 0.2 and 2 mg/kg, respectively), whereas all doses depressed the initial high motor activity. Probably, high motor activity requires active dopamine neurones, making this behaviour more susceptible to interference with autoregulatory mechanisms, whereas a low basal activity may be more affected by activation of postsynaptic dopamine receptors.
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PMID:Catecholamine receptor agonists: effects on motor activity and rate of tyrosine hydroxylation in mouse brain. 18 81

Pressure increases elicited by contractions of the circular muscle of the isolated guinea-pig vas deferens in response to nerve stimulation were recorded. In contrast to longitudinal muscle which contracted in response to 1--50 pulses, circular muscle responded only to longer trains of pulses (10--500) at a frequency of 10 Hz. Atropine (1.4 muM) caused a slight depression of responses to 100 shocks. Phentolamine at a concentration of 2.6 muM failed to inhibit the response to stimulation, but a higher concentration (53 muM) caused a definite blockade. Guanethidine (25 muM) strongly reduced the responses. With a stimulus train of 100 pulses no inhibition by prostaglandin E1 (PGE1) (0.028 muM) could be demonstrated; however, at a lower number of shocks (20--50) a clearcut depression was observed. The lower the number of pulses the more marked was the depression. The observation that PGE1 failed to block the contractions evoked by noradrenaline (59 muM) suggests a presynaptic inhibitory action of the prostaglandin. It is suggested that noradrenaline is the transmitter in both muscle coats of the guinea-pig vas deferens and that the neuroeffector junctions are sensitive to the effect of PGE1.
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PMID:Inhibition of neuromuscular transmission by prostaglandin E1 in the circular muscle of the guinea-pig vas deferens. 18 81

1. Responses of cerebral cortical neurones to the microiontophoretic application of acetylcholine, noradrenaline, cyclic adenosine 3',5'-monophosphate (cyclic AMP) and cyclic guanosine 3',5'-monophosphate (cyclic GMP) were examined.2. The application of acetylcholine and cyclic GMP to identified pyramidal tract neurones resulted in an increased frequency of firing in a large number of cells. Upon application of both substances to cells which could not be identified as pyramidal tract cells, a reduction in the frequency of spontaneous firing was sometimes observed.3. Careful current controls had no effect on the cells discussed here, indicating that the observed responses were not due to the iontophoretic currents. Also, the electro-osmotic ejection of cyclic GMP (outward current) produced similar changes of cell firing to those which followed iontophoretic application (inward current).4. The microiontophoretic application of atropine resulted in a blockade of acetylcholine responses while leaving responses to cyclic GMP unaffected. This suggests that cyclic GMP was not acting indirectly by releasing acetylcholine from presynaptic endings.5. Ejection of cyclic GMP from solutions containing calcium ions produced responses comparable to those produced by cyclic GMP alone. It is unlikely therefore that cyclic GMP was causing excitation by chelating calcium.6. Applications of noradrenaline and cyclic AMP produced a reduction in the spontaneous discharge rate of most neurones tested.7. Phosphodiesterase inhibitors such as ICI 63,197 caused a potentiation of the noradrenaline responses of pyramidal tract neurones.8. 5'-adenosine monophosphate produced a powerful depression of all cells to which it was applied. This action was blocked by aminophylline, suggesting the effect was mediated through an adenosine receptor. Responses to cyclic AMP were usually not abolished, but were reduced by about 50% in amplitude.9. These results are consistent with the hypothesis that cyclic AMP may mediate some neuronal effects of noradrenaline and cyclic GMP may mediate some effects of acetylcholine. The results are also consistent with the suggestion that the two nucleotides may sometimes mediate opposite cellular responses to humoral stimuli.
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PMID:Microiontophoretic studies of the effects of cylic nucleotides on excitability of neurones in the rat cerebral cortex. 19 28

With the use of an organ redoximeter, the effects of noradrenaline, adrenaline, isoproterenol, and phenylephrine on the oxidation-reduction state of the myocardial pyridine nucleotides were studied in the canine heart-lung preparation supported by a donor. Noradrenaline and adrenaline produced an initial, transient improvement, and phenylephrine a sustained improvement, of the redox state, while isoproterenol produced a depression. Pretreatment of the preparation with adrenergic alpha-blockers resulted in an abolishment of the improvement by noradrenaline, adrenaline, and phenylephrine, while the depression by isoproterenol remained unchanged. Whereas noradrenaline and adrenaline produced a sustained improvement after an adrenergic beta-blocker, propranolol, the effect of isoproterenol was abolished. These findings suggest that sympathomimetic amines can produce an improvement of the myocardial energy metabolism through activation of the adrenergic alpha-receptor. The depression of the myocardial oxidation-reduction state was taken to represent an acceleration of glycolysis.
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PMID:Effects of catecholamines on myocardial energy metabolism as studied by an organ redoximeter. 20 89

1 The report of the depression by indomethacin of vasoconstrictor responses to noradrenaline and their partial restoration by prostaglandin E(2) (PGE(2)) and PGE(1) in rat isolated perfused mesenteric blood vessels was investigated. The further suggestion that prostaglandins may be necessary for the combination of noradrenaline with the alpha-adrenoceptor in this tissue was also studied.2 The reported depression by indomethacin was confirmed and was further shown to be in the form of a concentration-dependent flattening of the noradrenaline concentration-effect curve.3 A concentration-dependent restorative effect was observed for all prostaglandins studied. The decreasing order of potency for the restoration towards normal of the indomethacin-depressed responses to noradrenaline was: PGE(2), PGE(1), PGA(1), PGF(2alpha), PGA(2).4 The prostaglandins studied were not uniform in their restorative actions and could be separated into two groups. PGE(2) and PGE(1) restored responses towards the control level whereas PGA(1), PGA(2) and PGF(2alpha) increased responses to an above control level and did so over a smaller concentration range. The possibility of several prostaglandin receptors is discussed.5 At concentrations equi-effective in restoring depressed responses to control levels PGA(1) but not PGE(2), caused a parallel shift of the noradrenaline concentration-effect curve to the left and a small, gradual rise in the basal perfusion pressure.6 The reason for the differing effects remains obscure but does not seem to involve a change in the alpha-adrenoceptor as indicated by the pA(2) of phentolamine. Furthermore, the restorative and potentiating effect of PGA(1) is not mediated by blockade of neuronal uptake of noradrenaline.7 It appears that prostaglandins are required for the vasoconstrictor action of noradrenaline in rat mesenteric blood vessels and that this effect is distal to the drug-receptor interaction. The possible involvement of prostaglandins with intracellular calcium ions is discussed.
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PMID:The influence of prostaglandins on noradrenaline-induced vasoconstriction isolated perfused mesenteric blood vessels of the rat. 20 65

1. The effects of phenol and phenyl glucuronide on the responses of normal rat brain adenyl cyclase to noradrenaline and dopamine have been investigated. Neurotransmitter responses have also been examined in brains from uraemic and normal rats. 2. A depressive effect of phenol on the adenosine 3' :5' -cyclic monophosphate response of the neostriatum to dopamine was shown to be completely abolished if the toxin was present in the conjugated form; the response of the cortex to noradrenaline was stimulated by the presence of phenyl glucuronide, even though the unconjugated form had no effect. 3. The uraemic state in the rat also resulted in a depression of the neostriatum response to dopamine, yet an enhancement of the cortical response to noradrenaline. 4. The action of phenols of the brain is relevant to hepatic and uraemic coma.
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PMID:Effect of unconjugated and conjugated phenol and uraemia on the synthesis of adenosine 3' :5' -cyclic monophosphate in rat brain homogenates. 21 46

Hyperactivity produced in mice with morphine or fentanyl, and methylamphetamine was antagonized by naloxone. The depression of locomotor activity induced by codeine was practically unchanged by the opiate antagonist. L-DOPA did not restore the stimulatory action of morphine and fentanyl in reserpinized mice. The hyperactivity produced by morphine and fentanyl was abolished in mice treated with alpha-methyl-p-tyrosine, but this was restored by L-DOPA administration. Agents inhibiting the central noradrenaline receptors, phentolamine, phenoxybenzamine, and aceperone, prevented or even reversed the locomotor stimulatory action of morphine and fentanyl. Pimozide did not affect the increase of locomotor activity produced by morphine, but depressed that induced by fentanyl. Haloperidol, used in a dose which did not affect the locomotor activity of mice, completely blocked or even reversed the stimulatory action of morphine and fentanyl, and potentiated the depression of locomotor activity produced by pentazocine and codeine. Diethyldithiocarbamate significantly depressed, but did not inhibit completely the stimulatory action of morphine and fetanyl. The stimulatory action of methylamphetamine was also significantly depressed. It seems that the stimulatory effect of morphine and fentanyl depends on the release of endogenous noradrenaline.
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PMID:Central action of narcotic analgesics. Part III. The role of endogenous noradrenaline in hyperactivity induced by morphine or fentanyl in mice. 21 79

In isolated strips of canine mesenteric vein prostacyclin (PGI2) causes a dose-dependent depression of the amplitude of the spontaneous rhythmic contractions without influencing their frequency. This suggests that prostacyclin affects the events leading from the depolarization of the smooth muscle cells to their contractions, rather than the induction of the myogenic activity itself. Furthermore, prostacyclin reduces the noradrenaline-induced contraction of the canine saphenous vein without affecting the electrically induced responses, suggesting a possible dual effect of the drug: at the smooth muscle it causes depression of the responsiveness to noradrenaline whereas at the adrenergic nerve endings it enhances the evoked release of the adrenergic transmitter.
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PMID:Effect of prostacyclin on myogenic activity and adrenergic neuroeffector interaction in canine isolated veins. 21 44


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