[3H]Dihydroergocryptine binding in rat brain

Davis, James N.; Strittmatter, Warren J.; Hoyler, Elizabeth; Lefkowitz, Robert J.

doi:10.1016/0006-8993(77)90425-5

Cited by 68 publications

(12 citation statements)

References 6 publications

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“…In addition, the kinetic studies reported here give a Kd which differs from the Kd calculated from equilibrium studies. Three previous studies have reported kinetically derived Kds that were consistently two-to threefold less than the Kd derived from equilibrium data in rabbit uterus (7), rat parotid cells (10), and rat brain (18). In view of these observations and of the present data, the possibility must be considered that [3H]DHEC binding is more complex than a simple bimolecular reaction with the a-adrenergic receptor.…”

Section: Methodssupporting

confidence: 40%

Characterization of the Human Platelet α-Adrenergic Receptor

Alexander¹,

Cooper²,

Handin³

1978

J. Clin. Invest.

126

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A B S T R A C T Human platelets aggregate and undergo a release reaction wvhen inetubated wvith catecholamines. Indirect evidence indicates that these events are mediated through a-adrenergic receptors. We used [3H]dihydroergocryptine, an a-adrenergic antagonist, to identify binding sites on platelets that have the characteristics of a-adrenergic receptors. Catecholamines compete for the binding sites in a stereo-specific manner with the potency series of (-) epinephrine > (-) norepinephrine > (+) phenylephrine > (-) isoproterenol. The dissociation constant (Kd) of (-) ,M. Phentolamine and dihydroergocyrptine blocked this response, whereas (±) propranolol had no effect. (-) Epinephrine and (-) norepiniephrine inhibited basal and prostaglandin El-stimulated adenylate cyclase in a dose-related manner. The conicentrationi of( -) epiinephrinie inhibiting adenvlate cyclase 50% was 0.7 ,uM. This inhibitioni was also blocked by phentolamiiine and dihydroergocryptine btut not by (±) propranolol. The specificity of binding and the close correlationi with a-adrenergic receptor-mediated biochemical and physiological responses suggest that the [3H]dihydroergocryptine binding site represents, or is closely related to, the human platelet a-adrenergic receptor. The ability to assay this receptor directly and to correlate these data with independently measured se(uelae of receptor activation should facilitate increased understandinig of the physiology and pathophysiology of the hulmlani platelet a-adrenergic receptor.

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Section: Methodssupporting

confidence: 40%

Characterization of the Human Platelet α-Adrenergic Receptor

Alexander¹,

Cooper²,

Handin³

1978

J. Clin. Invest.

126

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“…on LH release mediated by an a-adrenoceptor and an inhi bition mediated by a fi-adrenoceptor. Both a-and (1-adreno ceptors have been demonstrated in the hypothalamus al though their precise location has not been described yet [1,5,6].…”

Section: Discussionmentioning

confidence: 99%

Dissociation of the Inhibitory and Facilitatory Effects of Norepinephrine on the Release of LH by Premammillary Lesions

Cáceres¹,

Taleisnik²

1982

Neuroendocrinology

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A dual action of the adrenergic system on the release of LH has been demonstrated: facilitation mediated by α-adrenergic receptors and inhibition mediated by β-adrenergic receptors. These two actions can be dissociated either by treatment with agents which block-specific adrenergic receptors or by cuts placed just in front of the mammillary bodies (PM cuts) interrupting caudal afferents to the medial basal hypothalamus. These cuts affected the release of luteinizing hormone (LH) in a way similar to that of treatment with the β-adrenoblocker, propranolol. Thus, in animals with PM cuts (1) the release of LH following the injection of norepinephrine into the third ventricle was enhanced and (2) the blocking action of intraventricular injection of isoproterenol on the release of LH was suppressed whereas the facilitatory effect of clonidine was not changed. Furthermore, whereas the release of LH induced by intraventricular injection of norepinephrine in intact rats was enhanced by treatment with propranolol, in rats with PM cuts the already enhanced induced release was no further rised by propranolol treatment. On the other hand, PM cuts did not affect the suppressive action of the α-adrenoblocker phenoxybenzamine on the norepinephrine-induced release of LH. It is concluded that adrenergic mechanisms inhibiting the release of LH were suppressed by PM cuts whereas those facilitating the release were not affected by these cuts.

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“…The KD for [3HpDHE was 0.55 nM (with or without phentolamine), and this high affinity site was blocked (in the presence of phentolamine) by 250 nM apomorphine, 650 nM dopamine, and 1200 nM (-). Although it is now possible to use [3H]dopamine, [3H]apomorphine, and [3H]haloperidol for identifying dopamine receptors in biological tissues (1)(2)(3)(4)(5)(6)(7), it is desirable to have additional radioligands in order to test the two-state agonist-antagonist receptor hypothesis (3,5 (8)(9)(10)(11) are difficult to interpret.…”

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confidence: 99%

New detection of brain dopamine receptors with (3H)dihydroergocryptine.

Tittler¹,

Weinreich²,

Seeman³

1977

Proc. Natl. Acad. Sci. U.S.A.

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Because dihydroergocryptine (DHE) (13,14) have found that DHE acts as a pure dopamine-like agonist on pituitary cells in culture. It is also known that 2-bromocryptine, which is chemically similar to DHE, has dopamine-like agonist activity on rat behavior (15), mimicks the effect of L-3,4-dihydroxyphenylalanine on patients with Parkinson disease (16), and reduces prolactin secretion in patients in a fashion similar to other dopamine-mimetic drugs (17).These previous studies on the ergot compounds (13)(14)(15)(16)(17) METHODS AND MATERIALS Preparation of Calf Caudate Homogenates. The experiments were done on crude homogenates of calf caudate, prepared as described (6). In order to retain all the dopamine receptors, the homogenates were not purified or subfractionated. Calf brains were obtained fresh from the Canada Packers Hunnisett plant (Toronto, Canada). The caudates were removed within 2 hr after death, pooled, sliced into small cubes, and suspended in buffer at an approximate concentration of 50 mg of wet weight per ml of buffer. The buffer contained 15 mM Tris-HCI (pH 7.4), 5 mM Na2EDTA, 1.1 mM ascorbate, and 12.5 ,uM nialamide. A preliminary crude homogenate of the suspension was made with a glass homogenizer with a Teflon piston (0.13-0.18 mm clearance). This piston, rotating at 500 rpm, was passed up and down 20 times in the homogenizer. The crude homogenate was first incubated at 370 for 60 min and then stored in 3-ml aliquots at -20°for future use. Before using, the samples were thawed, resuspended in the glass-Teflon homogenizer and homogenized by hand (10 upand-down passes), and centrifuged at 39,000 X g for 15 min at 40; the supernatant was discarded and the pellet was resuspended in 10 ml of buffer. The suspension was finally homogenized by a Polytron homogenizer (Brinkman Instrument Co.) at a setting of 7 (full range = 10) for 20 sec, by using a PT-10 homogenizer probe and a 50-ml polycarbonate tube to contain the suspension. Homogenization at settings higher than 7 led to a loss of protein through the glass fiber GF/B filters used in the radioreceptor assays. Except were indicated, the homogenates were always kept chilled on ice.[

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[3H]Dihydroergocryptine binding in rat brain

Cited by 68 publications

References 6 publications

Characterization of the Human Platelet α-Adrenergic Receptor

Characterization of the Human Platelet α-Adrenergic Receptor

Dissociation of the Inhibitory and Facilitatory Effects of Norepinephrine on the Release of LH by Premammillary Lesions

New detection of brain dopamine receptors with (3H)dihydroergocryptine.

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