Alpha-2 adrenergic regulation of norepinephrine release in the rat submandibular gland as measured by HPLC-EC

Turner, John T.; Pierce, Dan L.; Bylund, David B.

doi:10.1016/0024-3205(84)90396-5

Cited by 19 publications

(8 citation statements)

References 11 publications

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“…Again, the effect of phenylephrine was antagonized by prazosin, although less efficiently than by yohimbine. Thus, as well as in the cardiac adrenergic terminals of several animal species (Kobinger & Pichler, 1980;Docherty, 1983;Ledda & Mantelli, 1984 (Neylon & Summers, 1985;Harrison et al, 1991) including those of rat submandibular gland tissue slices and rat brain slices (Turner et al, 1984;Nasseri & Minneman 1987 . Only the effect of the imidazolines however is completely antagonized by M2-blockers, while noradrenaline shows a 'remaining effect' which is insensitive to a(X-, a2-or P-adrenoceptor blockers (Bond et al, 1986a;b).…”

Section: Discussionmentioning

confidence: 99%

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α.‐Adrenoceptor modulation of the efferent function of capsaicin‐sensitive sensory neurones in guinea‐pig isolated atria

Amerini

Rubino

Mantelli

et al. 1992

British J Pharmacology

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1 Transmural nerve stimulation of guinea-pig atria, obtained from animals pretreated with reserpine (5 mg kg-', i.p.), in the presence of atropine 1 JAM and of the 13-adrenoceptor blocker CGP 20712A 1 JAM, induced a positive inotropic effect which was reduced by the calcitonin gene-related peptide (CGRP) antagonist hCGRP-(8-37) and abolished by pretreatment with capsaicin 1 JM.2 Noradrenaline concentration-dependently (0.01-10 JAM) reduced the increase in cardiac contractility induced by transmural nerve stimulation. The inhibitory effect of noradrenaline was antagonized by yohimbine (0.5-1 JM), in a dose-dependent manner. Prazosin (0.5-1 JAM) antagonized the effect of noradrenaline and this effect was independent of concentration. 3 In the presence of yohimbine, the lower part of the inhibitory-response curve for noradrenaline was slightly but significantly shifted by prazosin. A similar degree of antagonism was observed in the presence of 1 JAM phenoxybenzamine. 4 The selective X2 agonists BHT 920 and clonidine reduced, in the same concentration-range (0.01-1 JAM), the cardiac response to transmural nerve stimulation in a yohimbine-sensitive fashion.5 Phenylephrine (0.1-100 JAM) and methoxamine (1-300 JAM) also induced an inhibitory effect on transmural nerve stimulation. The effect of phenylephrine was antagonized by yohimbine (1 JM) more efficiently than by prazosin (0.5 JM). 6 These results are in keeping with the presence of inhibitory prejunctional a2-adrenoceptors on cardiac sensory nerve endings which modulate the efferent function of capsaicin-sensitive neurones.

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Section: Discussionmentioning

confidence: 99%

“…[3H]-rauwolscine binding sites in several membrane preparations (Neylon & Summers, 1985;Harrison et al, 1991) including those of rat submandibular gland tissue slices and rat brain slices (Turner et al, 1984;Nasseri & Minneman 1987).…”

Section: Discussionmentioning

confidence: 99%

α.‐Adrenoceptor modulation of the efferent function of capsaicin‐sensitive sensory neurones in guinea‐pig isolated atria

Amerini

Rubino

Mantelli

et al. 1992

British J Pharmacology

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“…Furthermore binding studies suggest that about 60% of a2-adrenergic receptors in rat cerebral cortex are of the subtype (Bylund, 1988). Of particular interest are studies on the different potencies of prazosin and yohimbine on NA release from rat submandibular gland tissue slices (Turner et al, 1984) and rat cerebral cortex (Nasseri and Mineman, 1987) which suggest that NA release is regulated by azB-adrenergic receptor subtypes (Bylund, 1988). It will be of interest to compare the potencies of prazosin and yohimbine on NA release from occip ital cortex chops to determine which a2-adrenergic receptor subtype is involved.…”

Section: Discussionmentioning

confidence: 99%

Regulation of Noradrenaline Release from Rat Occipital Cortex Tissue Chops by α₂‐Adrenergic Agonists

Ong

Ball

Vaughan

1991

Journal of Neurochemistry

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Noradrenaline (NA) and the alpha 2-adrenergic agonists clonidine, BHT-920, and UK 14304-18 inhibit potassium-evoked release of [3H]NA from rat occipital cortex tissue chops with similar potencies. NA (10(-5) M) was most effective as up to 85% inhibition could be observed compared with 75%, 55%, and 35% for UK 14304-18, clonidine, and BHT-920, respectively, all at 10(-5) M. Potassium-evoked release was enhanced by both forskolin (10(-5) M) and 1 mM dibutyryl cyclic AMP. Pretreatment of tissue chops with 1 mM dibutyryl cyclic AMP in the presence of 3-isobutyl-1-methylxanthine partially reversed the alpha 2-adrenergic agonist inhibition of NA release. No reversal of inhibition was observed following pretreatment with 10(-5) M forskolin. The effects of clonidine, BHT-920, UK-14308-18, and NA on cyclic AMP formation stimulated by (a) forskolin, (b) isoprenaline, (c) adenosine, (d) potassium, and (e) NA were examined. Only cAMP formation stimulated by NA was inhibited by these alpha 2-adrenergic agonists. These results suggest that only a small fraction of adenylate cyclase in rat occipital cortex is coupled to alpha 2-adrenergic receptors. These results are discussed in relation to recent findings that several alpha 2-adrenergic receptor subtypes occur, not all of which are coupled to the inhibition of adenylate cyclase, and that alpha 2-adrenergic receptors inhibit NA release in rat occipital cortex by a mechanism that does not involve decreasing cyclic AMP levels.

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“…Other authors have found that prazosin has relatively high potency at the prejunctional a2-adrenoceptors of rat submandibular gland (Turner et al, 1984), rat cerebral cortex (Nasseri & Minneman, 1987) and rabbit pulmonary artery (Kapocsi et al, 1987), suggesting that the prejunctional a2-adrenoceptors in these tissues may resemble the a2B-ligand binding site. The low potency of prazosin prejunctionally at the cholinergic nerves of guinea-pig ileum (Kapocsi et al, 1987) suggests that this receptor may resemble the a2A-ligand binding site.…”

Section: Discussionmentioning

confidence: 99%

“…Prazosin, which has higher absolute potency and higher potency relative to yohimbine at the a2B-than at that a2A-binding site, has been shown to be only 5 times less potent than yohimbine in potentiating the stimulation-evoked release of noradrenaline in rat submandibular gland (Turner et al, 1984) and rat cerebral cortex (Nasseri & Minneman, 1987), suggesting that these receptors may resemble the a2B-binding site. Furthermore, Kapocsi et al (1987) found that prazosin had higher potency at potentiating the stimulation-evoked release of noradrenaline from adrenergic nerves of rabbit pulmonary artery than from cholinergic nerves of guinea-pig ileum, suggesting that different subtypes of X2-adrenoceptor are present on these nerve terminals.…”

Section: Rat Vas Deferens Isometric Contractionmentioning

confidence: 99%

Functional evidence for heterogeneity of peripheral prejunctional α₂‐adrenoceptors

Connaughton

Docherty

1990

British J Pharmacology

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1 We have examined the potencies of a series of a2-adrenoceptor antagonists in functional studies of prejunctional x2-adrenoceptors in rat atrium and vas deferens, and compared potencies with affinities for the a2A-ligand binding site of human platelet and the a2B-site of rat kidney. 49, 12 and 7 times higher potency in rat atrium, respectively. ARC 239 was also 17 times more potent in rat atrium than rat vas deferens when EC30 values were compared. 5 The correlation of affinity for the a2A-site of human platelet was better with prejunctional potency. in rat vas deferens than rat atrium. 6 The correlation of affinity for the CX2B-site of rat kidney was better with prejunctional potency in rat atrium than rat vas deferens. 7 It is concluded that prejunctional a2-adrenoceptors of rat vas deferens and rat atrium differ, and these receptors may resemble the Oe2A-and a2B-ligand binding sites, respectively.

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Alpha-2 adrenergic regulation of norepinephrine release in the rat submandibular gland as measured by HPLC-EC

Cited by 19 publications

References 11 publications

α.‐Adrenoceptor modulation of the efferent function of capsaicin‐sensitive sensory neurones in guinea‐pig isolated atria

α.‐Adrenoceptor modulation of the efferent function of capsaicin‐sensitive sensory neurones in guinea‐pig isolated atria

Regulation of Noradrenaline Release from Rat Occipital Cortex Tissue Chops by α₂‐Adrenergic Agonists

Functional evidence for heterogeneity of peripheral prejunctional α₂‐adrenoceptors

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Alpha-2 adrenergic regulation of norepinephrine release in the rat submandibular gland as measured by HPLC-EC

Cited by 19 publications

References 11 publications

α.‐Adrenoceptor modulation of the efferent function of capsaicin‐sensitive sensory neurones in guinea‐pig isolated atria

α.‐Adrenoceptor modulation of the efferent function of capsaicin‐sensitive sensory neurones in guinea‐pig isolated atria

Regulation of Noradrenaline Release from Rat Occipital Cortex Tissue Chops by α2‐Adrenergic Agonists

Functional evidence for heterogeneity of peripheral prejunctional α2‐adrenoceptors

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Product

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Regulation of Noradrenaline Release from Rat Occipital Cortex Tissue Chops by α₂‐Adrenergic Agonists

Functional evidence for heterogeneity of peripheral prejunctional α₂‐adrenoceptors