Facilitation by Clonidine of Purine Release Induced by High Kc1 From the Rabbit Pulmonary Artery

Katsuragi, Takeshi; Su, Che

doi:10.1111/j.1476-5381.1981.tb10482.x

Cited by 19 publications

(6 citation statements)

References 17 publications

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“…A number of studies on different blood vessels have demonstrated, both mechanically and electrically, neurogenic responses that are not antagonized by oxadrenoceptor antagonists (see . It has been suggested that purines might play a role as cotransmitters with noradrenaline in some vessels (Su, 1975;Head et al, 1977;Katsuragi & Su, 1981;Muramatsu et al, 1981;Sedaa et al, 1986).…”

Section: Introductionmentioning

confidence: 99%

A pharmacological study of the rabbit saphenous artery in vitro: a vessel with a large purinergic contractile response to sympathetic nerve stimulation

Burnstock

Warland

1987

British J Pharmacology

126

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1 Mechanical responses to transmural electrical stimulation were recorded in isolated transverse ring preparations of rabbit saphenous artery. Electrical stimulation for a period of 1 s produced a rapid monophasic contraction and, for a period of 1 min, a biphasic contraction consisting of a rapid constriction followed by a slower sustained constriction. All contractions were abolished in the presence of tetrodotoxin (1 glg ml-') or guanethidine (4 JiM).2 After desensitization of the P2-purinoceptor with aj-methylene ATP, contractions to electrical stimulation for 1 s were reduced significantly at all frequencies tested: responses evoked by stimulation at 4 Hz were usually almost completely inhibited, whereas those evoked by stimulation at 64 Hz were only partially inhibited. On the other hand, in the presence of the a-adrenoceptor antagonist, prazosin, neurogenic contractions were only partially reduced: at 4 Hz there was no significant reduction in the neurogenic contractions while at 32 and 64 Hz, contractions were reduced by an average of20 and 28% respectively. Usually all contractions were abolished by a combination of the two drugs. 3 Prazosin antagonized contractions of the vessel to exogenously applied noradrenaline but not to ATP, whereas desensitization of the P2-purinoceptor with a,-methylene ATP blocked responses to ATP but not those to noradrenaline. The concentration-response curve to histamine was not affected by treatment of the vessel with prazosin, or after desensitization of the P2-purinoceptor with ax,fmethylene ATP. 4 These results suggest that noradrenaline and ATP are co-released from sympathetic nerves supplying the rabbit saphenous artery, both substances being involved in the mechanical contractions of this tissue. Further, the ratio of ATP to noradrenaline involved in these mechanical contractions is dependent upon the frequency of stimulation, but at all frequencies tested the purinergic component is greater than the adrenergic component.

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Section: Introductionmentioning

confidence: 99%

A pharmacological study of the rabbit saphenous artery in vitro: a vessel with a large purinergic contractile response to sympathetic nerve stimulation

Burnstock

Warland

1987

British J Pharmacology

126

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“…Clonidine (3 x mol/l) elicited a sustained contraction of the rabbit pulmonary artery as briefly reported by Katsuragi & Su (1981). Clonidine also reversed the contractile response to adrenaline (3 x mol/l) in the superfused vascular segment and adrenaline thereafter caused a relaxation which was abolished by pretreatment with a 0-adrenoceptor blocker, propranolol.…”

Section: Discussionmentioning

confidence: 62%

“…However, clonidine is also capable of inducing a contractile response in a variety of tissues, particularly vascular smooth muscle (Katsuragi & Su, 1981).…”

Section: Introductionmentioning

confidence: 99%

“…From many studies on the presynaptic autoreceptor modulating catecholamine release from noradrenergic nerves, clonidine is well accepted as a typical presynaptic a*-adrenoceptor agonist (Lager, 1977;Starke, 1977). However, clonidine is also capable of inducing a contractile response in a variety of tissues, particularly vascular smooth muscle (Katsuragi & Su, 1981).…”

Section: Introductionmentioning

confidence: 99%

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Reversal of Adrenaline‐induced Contraction in the Rabbit Pulmonary Artery by Clonidine

Katsuragi

Mori

et al. 1984

Clin Exp Pharma Physio

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Characterization of clonidine which reversed the adrenaline-induced contractions was assessed using the rabbit pulmonary arterial segment. Clonidine in high concentrations (10(-5)-10(-4) mol/l) contracted this vascular tissue. Nevertheless, an adrenaline (3 X 10(-6)mol/l)-induced contraction, which can be markedly depressed by phentolamine, was reversed to relaxation by pre-addition of 3 X 10(-5)mol/l clonidine. This reversal was abolished by 10(-5) mol/l propranolol, a beta-adrenoceptor antagonist. The cumulative concentration-contraction curve for adrenaline was shifted to the right by 10(-5) mol/l clonidine without further alteration at 10(-4) mol/l, suggesting a partial agonistic feature of clonidine for alpha-adrenoceptors. Contractions evoked by 5 X 10(-5) mol/l clonidine alone were effectively reduced by prazosin (IC50 = 1.7 X 10(-7) mol/l) or yohimbine, (IC50 = 3.3 X 10(-5) mol/l) and those by phenylephrine (10(-5) mol/l) were suppressed as well (prazosin, IC50 = 3.4 X 10(-8) mol/l; yohimbine, IC50 = 5.0 X 10(-6) mol/l). However, the depolarization-induced contractions with 30 mmol/l KCl were virtually unaltered by both antagonists. These results suggest that the reversal action of clonidine on the adrenaline-induced contraction is primarily mediated by a partial agonistic property for postsynaptic alpha 1-adrenoceptors.

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“…Many workers have suggested that ATP is a co-transmitter with NA in sympathetic nerves supplying blood vessels (Su, 1975;Head et al, 1977;Katsuragi & Su, 1981;Muramatsu et al, 1981;Sedaa et al, 1986;Burnstock, 1988). Sympathetic nerve stimulation has been shown to produce contraction mediated by both NA and ATP in the rat tail artery (Sneddon & Burnstock, 1984;Vidal et al, 1986), the mesenteric artery (Ishikawa, 1985;von Kugelgen & Starke, 1985;Muramatsu, 1986), the rabbit ear artery (Kennedy et al, 1986), the rabbit saphenous artery (Burnstock & Warland, 1987) and the dog basilar artery (Muramatsu & Kigoshi, 1987).…”

Section: Basal Tone Preparationsmentioning

confidence: 99%

Vasodilator response of coronary smooth muscle to the sympathetic co‐transmitters noradrenaline and adenosine 5′‐triphosphate

Corr

Burnstock

1991

British J Pharmacology

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1 Vasodilator and vasoconstrictor responses to noradrenaline (NA), adenosine and adenosine 5'-triphosphate (ATP) were examined in isolated ring segments of the left anterior descending coronary artery of the rabbit in the absence of endothelium.2 NA caused dose-dependent relaxation of potassium-constricted vessels in the absence of aladrenoceptor blockade, with a pD2 of 5.96 + 0.21. This was inhibited by 1 gM propranolol. Constrictor responses of vessels at baseline tension were only seen at concentrations greater than 1 mm, and reached a maximum of 6% of the contraction to 30 mm KCI. 3 ATP caused relaxation of the potassium-constricted ring segments in a dose-dependent manner, although a transient constriction often preceded the relaxation. Adenosine was equipotent with ATP in producing relaxation; this was significantly inhibited by the Pl-purinoceptor antagonist, 8-phenyltheophylline (8-PT). The responses to ATP were little affected by 8-PT, indicating that ATP was not acting through breakdown to adenosine. At basal tone, ATP produced transient vasoconstriction only at concentrations greater than 0.1 mm, reaching a maximum of 38% of the contraction to 30mM KCl. 4 We conclude that in the rabbit coronary artery both NA and ATP produce vasodilatation by a direct action on the smooth muscle.

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Facilitation by Clonidine of Purine Release Induced by High Kc1 From the Rabbit Pulmonary Artery

Cited by 19 publications

References 17 publications

A pharmacological study of the rabbit saphenous artery in vitro: a vessel with a large purinergic contractile response to sympathetic nerve stimulation

A pharmacological study of the rabbit saphenous artery in vitro: a vessel with a large purinergic contractile response to sympathetic nerve stimulation

Reversal of Adrenaline‐induced Contraction in the Rabbit Pulmonary Artery by Clonidine

Vasodilator response of coronary smooth muscle to the sympathetic co‐transmitters noradrenaline and adenosine 5′‐triphosphate

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