[A case of Dejerine-Sottas disease with central nervous system involvement].
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Adult↗
Biomedical subjects
T Katsuragi
Publications and source records attributed to T Katsuragi.
Possible transsynaptic cholinergic neuromodulation by ATP released from ileal longitudinal muscles of guinea pigs.
The effects of alpha, beta-methylene ATP (alpha, beta-mATP) and beta, gamma-methylene ATP (beta, gamma-mATP) on endogenous acetylcholine (ACh) release evoked by electrical nerve stimulation were evaluated in guinea-pig ileal longitudinal muscles. Release of ACh was measured with an HPLC-electrochemical detector system and release of ATP by luciferin-luciferase assay. Electrically evoked endogenous ACh release was reduced by both alpha, beta-mATP and beta, gamma-mATP at concentrations of 3 and 30 microM. The inhibitory effect of alpha, beta-mATP (30 microM) on ACh release was not detectable in the presence of theophylline (100 microM), a P1-purinoceptor antagonist, that itself enhanced ATP release. When exogenous ATP (0.1 microM) was added to the bath in which the ileal segment was suspended, it was rapidly metabolized, presumably by ecto-ATPase, and disappeared from the medium within 15 min. At 30 microM, alpha, beta-mATP induced ATP release in a suramin-sensitive but Ca(2+)- and atropine-insensitive manner, suggesting P2-receptor-mediated release of ATP from the smooth muscle. We conclude from these findings that alpha, beta-mATP and, probably, also beta, gamma-mATP, do not reduce ACh release by direct stimulation of presynaptic P1-purinoceptors, and that endogenous ATP released postjunctionally by these ATP analogs is decomposed metabolically to adenosine in the synapse and this adenosine triggers P1-purinoceptor sensitive neuromodulation of cholinergic transmission.
Acetylcholine↗
Implication of ATP released from atrial, but not papillary, muscle segments of guinea pig by isoproterenol and forskolin.
Effects of isoproterenol and forskolin, which increases intracellular cyclic AMP, on contraction and ATP release in atrial and papillary muscles of guinea pig were evaluated. In the electrically driven-left atrial muscle segments, isoproterenol and forskolin at 0.1 microM produced an ATP release coupled with a positive inotropic effect, the values of net ATP release at 5 min after these drugs being 5.20 +/- 0.59 and 5.37 +/- 0.55 nmoles/g wet weight, respectively. The forskolin evoked-ATP release was unaffected by prazosin plus propranolol or by guanethidine, implying that ATP is released from non-neuronal origin. In contrast, in papillary muscle segments, the test cardiotonics did not elicit any ATP release despite producing contractile response similar to that in atrial preparations. However, there is no difference in ectoATPase activities of both tissues. Adenosine added exogenously inhibited electrically evoked-contraction of the atrium, but not that of the papillary, although inhibitions by verapamil of the contractions were approximately equal in these preparations. These findings suggest that cardiotonics such as isoproterenol produce a liberation of ATP from auricle muscles, but not from ventricle muscles, and that the liberated ATP may mainly be catabolized to adenosine by ectoenzymes and the resultant nucleoside may serve as a functional modulator through stimulation of pre or postsynaptic A1-receptors.
Adenosine↗
Evidence for postjunctional release of ATP evoked by stimulation of muscarinic receptors in ileal longitudinal muscles of guinea pig.
The origin of the ATP release evoked by muscarinic agonists and veratridine from longitudinal muscles of the guinea pig was assessed with muscarinic antagonists. Acetylcholine (ACh) (1 microM) and bethanechol (10 microM) produced an immediate and marked ATP release, which was almost completely blocked by atropine (0.3 microM) and by the M3 muscarinic antagonist 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) (1 microM); release was only slightly affected by tetrodotoxin (0.6 microM). The bethanechol-evoked release of ATP was partly, but not significantly, inhibited by pirenzepine, a M1 muscarinic antagonist. Veratridine, an ACh releaser, also elicited a delayed ATP release, in a concentration-related manner. This ATP release was greatly antagonized by atropine and by Ca++ removal from the medium, implying mediation by endogenous ACh released after depolarization. In contrast, electrically evoked ACh release was enhanced by atropine and 4-DAMP. Bethanechol, unlike veratridine, failed to elicit measurable ACh release from the tissue. The contraction evoked by bethanechol was notably inhibited by atropine and 4-DAMP, but not by pirenzepine and AFDX-116, a M2 muscarinic antagonist, at a concentration of 0.3 microM. These findings suggest strongly that ATP is postjunctionally released from the ileal smooth muscles after stimulation of postsynaptic muscarinic receptors, presumably M3 receptors.
Acetylcholine↗
Hyperreactivity of alpha 1-adrenoceptors, but not of P2X-purinoceptors, in vas deferens of spontaneously hypertensive rats.
We evaluated the contractile reactivity to various stimuli, and the content and release of noradrenaline (NA) from a non-vascular tissue, the vas deferens, isolated from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). The concentration-contraction curves for NA in tissue from animals of two ages (10-25 weeks and 30-45 weeks) were shifted to the left in SHR as compared with in age-matched WKY, with significant differences at 1.0 and/or 10 microM of NA. Similarly, the amplitude of contraction produced by electrical stimulation at 4, 8 and 16 Hz in the tissue was much larger in SHR than in WKY. However, ATP (10-100 microM) evoked contractions of the tissue to a similar extent in both SHR and WKY. The electrically evoked contractions of vas deferens from both strains were inhibited by isoprenaline in an approximate dose-dependent and equipotent manner. The tissue NA content, determined by HPLC-ECD, was nearly same in both SHR and WKY. In addition, the same amount of NA was released from the vas deferens of both strains by electrical stimulation in the presence of 4-aminopyridine. The present findings indicate that the contractile response of vas deferens to stimulation of alpha 1-adrenoceptors, but not of beta-adrenoceptors or P2X-purinoceptors, is more pronounced in SHR than in WKY and that a response indicative of hypertension may also occur in non-vascular tissue as it does in vascular tissue.
Adenosine Triphosphate↗
Inhibition by ouabain and veratridine of acetylcholine-evoked phasic contraction in the guinea-pig taenia coli.
Inhibitory action of ouabain and veratridine on acetylcholine (ACh)-evoked phasic contraction was examined in the guinea-pig taenia coli. ACh (5 x 10(-4)M) produced a biphasic (phasic and tonic) contraction. As the phasic contraction, but not the tonic contraction, was resistant to gallopamil (D600, 2 x 10(-7)M), a blocker of voltage-dependent Ca2+ channels, all experiments were carried out in the presence of gallopamil at this concentration. Addition of high Ca2+ (30 mM) to the solution containing ACh induced a sustained contraction, which increased in the presence of ouabain (10(-5)M), an inhibitor of the Na(+)-K+ exchange system. On the other hand, the ACh-evoked phasic contraction was suppressed by ouabain (10(-7)-10(-5) M) in a time- and dose-dependent manner. The suppression by ouabain (10(-6)M) of the phasic contraction was transiently potentiated by the addition of veratridine (10(-6)M), an activator of Na+ channel. In contrast, the greater suppression by ouabain (10(-5)M) of the contraction was antagonized by amiloride (10(-4)M), a blocker of Na+ channel. This antagonism by amiloride was transiently inhibited in the presence of veratridine. In the absence of ouabain, the amplitude of the phasic contraction was transiently reduced by adding veratridine but was increased by amiloride. In addition, the phasic contraction by ACh increased 80 min after exposure to Na(+)-free isotonic high-K+ solution (K+, 143 mM), which elicited greater depolarization of the cell membrane. In a fluorescence study with Fura-2, an intracellular free-Ca2+ indicator, ACh increased the fluorescence intensity from the tissue by excitative light at 340 nm, which coupled with the phasic contraction.(ABSTRACT TRUNCATED AT 250 WORDS)
Acetylcholine↗
Involvement of K(+)-channel opening in endothelin-1 induced suppression of spontaneous contractions in the guinea pig taenia coli.
Effects of porcine-human endothelin-1 on mechanical as well as electrical activities and on intracellular free Ca2+ levels in the guinea pig taenia coli were compared with those of nifedipine, a voltage-dependent Ca2+ channel blocker. Endothelin-1 (0.1-100 nM) caused a concentration-dependent suppression of spontaneous contractions but did not significantly affect the sustained contraction evoked by 40 mM KCl. However, nifedipine (0.1-100 nM) inhibited both types of contractions in a concentration-dependent manner. In electrophysiological studies, endothelin-1 (30 nM) or nifedipine (30 nM) eliminated spontaneous spike discharges. Endothelin-1 produced hyperpolarization, while nifedipine did not change the resting membrane potential. The endothelin-1 induced suppression of spontaneous contractions was dose-dependently antagonized by apamin (0.01-10 nM), an inhibitor of a small conductance Ca(2+)-dependent K+ channel, and D-tubocurarine (10-100 microM), an inhibitor of Ca(2+)-dependent K+ channel, but was unaffected by 4-aminopyridine (0.01-1 mM), an inhibitor of a voltage-dependent K+ channel. In the study with fura 2 excited at 340 nm, endothelin-1 abolished, from the tissue, the fluorescence signals that were coupled with spontaneous contraction. It is suggested that the inhibitory action of endothelin-1 on spontaneous contraction may be caused by hyperpolarization of the membrane that reduces the spontaneous generation of spike discharge coupled normally to an increase in the intracellular free Ca2+ levels in the guinea pig taenia coli. The hyperpolarization may be caused by activating apamin-sensitive Ca(2+)-dependent K+ channels.
4-Aminopyridine↗
[The implication of stimulus-evoked ATP release from neuronal and extraneuronal sites].
Characteristics of the ATP release from non-neuronal tissues were reviewed in connection with that from neuronal tissues. alpha 1-Adrenoceptor and M3-cholinoceptor stimulation produced a postjunctional ATP release from smooth muscles such as the vas deferens and ileal longitudinal muscles of the guinea pig, suggesting the existence of a coupling mechanism between the stimulation of the receptor for the transmitter and postjunctional ATP release. Accompanied with positive inotropic action, cardiotonics elicit postjunctional ATP release, which is derived from mitochondria, in atrial muscles, whereas these drugs are incapable of producing the release from papillary muscles. Possible physiological roles of ATP released to synapses from nonneuronal tissues are considered as follows: 1) the nucleotide may act as an opener of Ca2+ and K+ channels, 2) ATP in the synapse seems to serve as a transsynaptic neuromodulator after conversion to adenosine.
Adenosine Triphosphate↗
Existence of ATP-evoked ATP release system in smooth muscles.
Effects of stable ATP analogs such as alpha,beta-methylene ATP (alpha,beta-mATP) and beta,gamma-methylene ATP (beta,gamma-mATP) on ATP release and contractile response were evaluated in the vas deferens and ileal longitudinal muscles of guinea pig. In these smooth muscles, administration of alpha,beta-mATP (10, 30 or 100 microM) produced an ATP release accompanied by a transient contraction, but alpha,beta-methylene ADP (30 or 100 microM) or adenosine (30 microM) failed to elicit both the ATP release and the contraction. However, the peak responses of ATP release and contraction to alpha,beta-mATP (100 microM) in the vas deferens appeared around 2 min and 2.62 sec, respectively, after the injection of the drug. Beta,gamma-mATP (10 or 100 microM) caused an ATP release from the vas deferens. The ATP release as well as the contraction evoked by alpha,beta-mATP or beta,gamma-mATP were effectively inhibited by 300 microM suramin, a P2 purinoceptor antagonist. By contrast, ATP release and contractile response to norepinephrine in the vas deferens and those to bethanechol in the ileum were virtually unaffected by this antagonist. Veratridine and ouabain at (30 or 100 microM) caused markedly acetylcholine release from the ileum and norepinephrine release from the vas deferens, respectively. However, alpha,beta-mATP, even in a high concentration of 100 microM, did not elicit any release of acetylcholine or norepinephrine. These findings suggest that alpha,beta-mATP and probably beta,gamma-mATP evoke ATP release from not neuronal but mainly smooth muscular sites by activating suramin-sensitive P2x receptors, implying that "ATP-evoked ATP release system" exists.
Acetylcholine↗
A possible coupling of postjunctional ATP release and transmitters' receptor stimulation in smooth muscles.
The nature of ATP release from mainly smooth muscles of guinea-pig was evaluated with KCl and agonists for different kinds of receptors. In ileal longitudinal muscles, amounts of net ATP release by ACh and bethanechol (1-10 microM) were much larger (about 10 fold) than that by other drugs, e.g., histamine, 5-hydroxytryptamine, prostaglandin-F2 alpha, substance P and bradykinin, including KC1, although differences between contractions of the tissue evoked by test drugs were approximately 1.5 times at most. The ATP release, as well as the contraction, evoked by ACh or bethanechol was markedly reduced by atropine (0.3 microM), thus, indicating primarily postjunctional release of ATP. The remarkable ATP release from vas deferens by norepinephrine (NE), but not by substance P, was abolished almost completely by prazosin (0.3 microM). Increases in intracellular Ca2+ and subsequent contraction in the ileal tissue were produced by ATP and these responses were fully antagonized by nifedipine (0.1 microM). These findings provide evidence that the drugs-stimulated ATP release from smooth muscles does not result from contractility of muscles, but is substantially elicited only by stimulation of neurotransmitter (NE or ACh) receptors, suggesting the existence of the receptor-stimulus-postjunctional ATP release coupling. The released ATP may contribute, in part, to the muscle contractility via increase of Ca2(+)-influx, presumably, in a manner related to the voltage-gated Ca2(+)-channels.
Acetylcholine↗
Involvement of dihydropyridine-sensitive Ca2+ channels in adenosine-evoked inhibition of acetylcholine release from guinea pig ileal preparation.
The effects of adenosine and nifedipine on endogenous acetylcholine (ACh) release evoked by electrical stimulation from guinea pig ileal longitudinal muscle preparations exposed to physostigmine were evaluated using an HPLC with electrochemical detection (ECD) system. Resting ACh release, which was sensitive to tetrodotoxin (0.3 microM), was enhanced by Bay K 8644 (0.5 microM; a Ca2+ antagonist) or 4-aminopyridine (30 microM; a K+ channel blocker) but not by theophylline (100 microM; a P1 purinoceptor antagonist) or atropine (0.3 microM). The enhancement of the resting ACh release by Bay K 8644 was virtually unaffected by atropine. Electrically evoked ACh release was enhanced by around two- to fourfold in the presence of theophylline, atropine, Bay K 8644, 4-aminopyridine, or atropine. On the other hand, the evoked ACh release was reduced by adenosine (10-30 microM), nifedipine (0.1-0.3 microM; a dihydropyridine Ca2+ channel antagonist), or bethanechol (1-3 microM) in a concentration-related fashion. The reduction induced by adenosine or nifedipine was almost abolished by either theophylline or Bay K 8644, whereas that induced by bethanechol was virtually unaffected by these drugs. The inhibition by adenosine of ACh release was not influenced in the presence of 4-aminopyridine or atropine. However, this inhibition by adenosine was considerably enhanced by halving the Ca2+ concentration in the Krebs solution and was diminished by doubling the Ca2+ concentration. These findings suggest that adenosine produces a cholinergic neuromodulation presumably via modifying dihydropyridine-sensitive Ca2+ channel activities in the cholinergic neurons, and thus L-type Ca2+ channels may exist on the nerve terminals.(ABSTRACT TRUNCATED AT 250 WORDS)
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
Antagonism by nifedipine of contraction and Ca2(+)-influx evoked by ATP in guinea-pig urinary bladder.
1. The effects of Ca2(+)-antagonists, especially nifedipine, on contraction and increase of intracellular Ca2+ (Fura-2/AM method) evoked by ATP were evaluated in a thin outer layer segment of guinea-pig urinary bladder. 2. The ATP-evoked contraction was markedly inhibited by dihydropyridine-type Ca2(+)-antagonists, such as nifedipine and nitrendipine, but not by D-600, omega-conotoxin and tetramethrin. 3. This antagonism by nifedipine of ATP-evoked contractions was competitive from the Schild plot analysis, the pA2 value being 8.23. The reduction of ATP-evoked contraction by nifedipine (0.1 microM) was fully reversed by administration of Bay K 8644 (0.1 microM). 4. ATP (100 microM) caused an increase of fluorescence brightness after loading Fura-2/AM, which was coupled with a contraction of the bladder. Both the contraction and the elevation of intracellular Ca2+ evoked evoked by the nucleotide were completely antagonized by nifedipine. by the nucleotide were completely antagonized by nifedipine. 5. These results suggest that ATP may activate the dihydropyridine-sensitive, voltage-dependent Ca2(+)-channels in a direct or indirect fashion and, thereby, elicit a contraction of the bladder.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
Heterogeneity of the effects of monensin on two types of contractions evoked by inhibition of Na+-K+ ATPase in the guinea-pig vas deferens.
The interactions between ouabain or K+-free medium and monensin on noradrenaline (NA) release and Ca2+-evoked contractions were assessed in guinea-pig vas deferens. Ouabain (10 microM) produced large, sustained contractions and monensin (1 microM) small, transient contractions. The ouabain-evoked contraction tended to be potentiated in the presence of monensin. The marked contraction induced by ouabain plus monensin was nearly abolished by phentolamine or by treatment with 6-hydroxydopamine. Ouabain caused the release of NA from the tissue, as determined in an HPCL-ECD study. This ouabain-evoked release of NA was enhanced by the simultaneous administration of monensin. High Ca2+ (10 mM) per se, ouabain, monensin or K+-free medium did not elicit contraction of the tissue in the presence of phentolamine. However, 10 mM Ca2+ caused a large contraction 45-65 min after exposure to ouabain or K+-free medium and this contraction was suppressed by monensin. The contraction evoked by Ca2+ in the presence of ouabain was further inhibited by amiloride, an inhibitor of Na+-Ca2+ or Na+-H+ exchange transport, but not by nifedipine, a voltage-dependent Ca2+ antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)
Amiloride↗
Two phases of the prostaglandin F2 alpha-induced contraction in guinea-pig taenia coli involve different Ca2+ channels.
Properties of the contraction produced by PGF2 alpha in the guinea-pig taenia coli were compared to those produced by ACh. Prostaglandin (PG) F2 alpha (3 x 10(-7) M) and acetylcholine (ACh, 10(-5)M) induced an initial transient contraction (phasic contraction) and a subsequent late contraction (tonic contraction). Both phasic and tonic contractions produced by PGF2 alpha or ACh were abolished in Ca2+ -free Krebs solution containing 0.5 mM EGTA. The tonic contractions caused by PGF2 alpha and ACh were markedly suppressed by alpha-[3-[[2-(3,4-dimethoxy-phenyl)-ethyl]-methylamino]-propyl]- 3,4,5-trimethoxy-alpha-(1-methylethyl)benzeneacetonitrile hydrochloride (D600, greater than 10(-7)M) as well as nifedipine (5 x 10(-9)M), a Ca2+-antagonist. However, the phasic contraction produced by PGF2 alpha, but not by ACh, was greatly inhibited by Mn2+ (greater than 10(-4)M). Furthermore, the phasic contraction caused by PGF2 alpha was abolished in 18 mM K+ Krebs solution with D600 (2 x 10(-7)M), whereas that induced by ACh and the tonic contractions produced by PGF2 alpha as well as by ACh were unaffected in this high K+ solution without D600. Membrane potentials of the tissue in normal (K+, 5.9 mM) and 18 mM K+ Krebs solution containing D600 were about -55 mV and -43 mV, respectively. In a fluorescence study which used Fura-2 an intracellular free Ca2+ indicator in the presence of D600, PGF2 alpha and ACh increased fluorescence intensity in the tissue, which coupled with the magnitude of contractions.(ABSTRACT TRUNCATED AT 250 WORDS)
Acetylcholine↗
Cardiovascular effects of 1-(3,4-dimethoxyphenyl)-2-(4-diphenylmethylpiperazinyl) ethanol and possible mechanisms involved.
Cardiovascular effects of NC-1100 (1-(3,4-dimethoxyphenyl)-2-(4-diphenylmethylpiperazinyl)ethanol and possible modes of action were studied in dogs and guinea pigs. 1. In pentobarbital-anesthetized dogs, intravenous administration of NC-1100 (0.05-1.6 mg/kg) induced a dose-dependent fall of blood pressure, a bradycardia followed by temporal tachycardia, a slight and transient stimulation of respiration and a prolongation of the R-R interval with slight augmentations of P, R and T waves in ECG. 2. In pentobarbital-anesthetized dogs, NC-1100 (2.5-80 micrograms/kg) administered to the maxillary and vertebral artery dose-dependently increased the blood flow in the respective artery. 3. Intravenous administration of NC-1100 (0.05-1.6 mg/kg) also exhibited dose-dependent increases of the maxillary and vertebral blood flow, though the increase in maxillary flow was a little reduced at a high dose of 1.6 mg/kg. Intravenous administration of NC-1100 (0.1-1.6 mg/kg) caused a slight increase in the aortic and coronary blood flow, a decrease in renal flow and a slight and transient decrease followed by an increase in femoral flow. 4. In pentobarbital-anesthetized dogs, NC-1100 (1 mg/kg) administered i.v. did not affect responses of blood pressure and heart rate to norepinephrine and isoprenaline (isoproterenol) but slightly inhibited hypotensive responses to acetylcholine. NC-1100 had no effect on hypertension elicited by carotid sinus reflex and on bradycardia by vagus stimulation. NC-1100 slightly inhibited the tachycardia elicited by pre- as well as postganglionic stellate stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Interaction between Bay-K-8644 and various relaxant agents on K+-depolarized contracture of guinea pig taenia coli.
1. Interaction between Bay-K-8644 and nifedipine, D600, diltiazem, papaverine or W-7 on a K+-contracture of the guinea pig taenia coli have been investigated. 2. These relaxing drugs except Bay-K-8644 inhibited the K+-contracture in a concentration-dependent manner. 3. Complete inhibition by nifedipine (1 x 10(-7) M) of the contracture was absolutely antagonized by Bay-K-8644 (1 x 10(-6) M), a Ca2+-agonist, an apparent pA2 value of Bay-K-8644 as an antagonist for nifedipine obtained from Schild plot being 7.94 and its slope 0.99. 4. Marked inhibitions by D600 (1 x 10(-5) M), diltiazem (1 x 10(-5) M), papaverine (1 x 10(-4) M) and W-7 (1 x 10(-4) M) were unaffected but mild inhibitions by around IC50 of these relaxing agents, except W-7, were fully antagonized by Bay-K-8644. 5. These results suggest that Bay-K-8644 is a competitive antagonist for nifedipine, but not for other agents, on common Ca2+ channel sites.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
Synergism between ouabain and monensin in neurogenic responses of guinea-pig vas deferens.
Interrelations between ouabain, a Na+-K+ ATPase inhibitor, and monensin, a Na+ ionophore, on noradrenaline liberation and contractile activity were evaluated in the guinea-pig vas deferens. Monensin (1 microM) per se elicited a small contraction of the tissue. However, amplitude and time to the peak of large and sustained contractions evoked by 10 microM ouabain were potentiated and markedly shortened, respectively, by monensin. Contractions elicited by ouabain with or without monensin were prevented by 3 microM phentolamine or by pretreatment with reserpine. Contractions evoked by K+-free solution were augmented by monensin. In an HPLC study, noradrenaline outflow from the vas deferens was moderately and considerably increased by monensin (10 microM) and ouabain (100 microM), respectively. The ouabain-evoked output of noradrenaline was enhanced in the presence of monensin and the time course for maximum noradrenaline release was shortened, as was the contractile activity. This enhanced outflow after ouabain plus monensin was reserpine sensitive but not tetrodotoxin sensitive. Furthermore, this noradrenaline outflow was roughly halved in Na+-deficient medium, but was unaltered in Ca2+-free medium. These findings suggest that the synergistic effect of ouabain and monensin on noradrenaline liberation from the guinea-pig vas deferens may be due to an elevation of cytoplasmic Ca2+ concentrations, presumably resulting from a stimulation of intracellular Na+-Ca2+ exchange system, but not enhanced Ca2+ entry.
Animals↗
Norepinephrine and adenosine triphosphate release in different ratio from guinea pig vas deferens by high potassium chloride, ouabain and monensin.
Release of norepinephrine (NE) and ATP from the guinea pig vas deferens evoked by ouabain in combination with monensin or by high KCl was measured by a high-pressure liquid chromatography-ECD and luciferin-luciferase assay, respectively. Ouabain (10-100 microM) induced a concentration-dependent liberation of NE, which was enhanced by 10 microM monensin, a Na+-ionophore. The marked NE release elicited by the combined administration of both the drugs was unaffected by Ca++-removal but was reduced by lowering Na+ from the medium. This NE release in the Ca++-free medium was diminished markedly after treatment with 6-hydroxydopamine or reserpine and in low-temperature (25 degrees C) medium. This release was also decreased by ruthenium red (10-30 microM), an uptake inhibitor of Ca++ to mitochondria, and carbonyl cyanide-m-chlorophenyl hydrazone (10 microM), a metabolic inhibitor. On the other hand, 100 mM KCl caused a moderate, extracellular Ca++-dependent release of NE. ATP-outflow from the tissue evoked by 100 microM ouabain plus 10 microM monensin was almost unaltered by Ca++-removal but was inhibited by 6-hydroxydopamine or prazosin (0.3 microM), whereas release induced by high KCl was reduced by 6-hydroxydopamine and Ca++-free medium but was unaffected by prazosin. ATP/NE ratios at respective maximum effluxes evoked by 100 mM KCl and ouabain plus monensin were 6.59 and 0.22, respectively. These findings suggest that there may be more than one site of corelease for NE and ATP. Ouabain plus monensin seems to produce an extracellular Ca++-independent neuronal release of NE and ATP from the cytoplasmic and vesicular storage sites which predominantly release NE.(ABSTRACT TRUNCATED AT 250 WORDS)
Adenosine Triphosphate↗