Attenuation of sympathetic vasoconstriction (sympatholysis) in working muscles during dynamic exercise is controversial. A potential mechanism is a reduction in alpha-adrenergic-receptor responsiveness. The purpose of this study was to examine alpha(1)- and alpha(2)-adrenergic-receptor-mediated vasoconstriction in resting and exercising skeletal muscle using intra-arterial infusions of selectiv...

We have used patch-clamp recording from cultured neurones, immunohistochemistry and gene deletion techniques to characterize the P2X receptors present in mouse otic ganglion neurones, and demonstrated the presence of similar receptors in rat neurones. All neurones from wild-type (WT) mice responded to ATP (EC(50) 109 microM), but only 38% also responded to alpha beta-meATP (EC(50) 39 microM). T...

The subcellular distribution of the alpha 2-adrenergic receptor, pertussis-toxin substrates (Gi, the inhibitory G-protein) and adenylate cyclase was determined in human platelets. The alpha 2-adrenergic receptor and pertussis-toxin substrate activity codistribute with surface membranes identified by a novel fluorescent-lectin method. The platelet granule fractions did not contain detectable Gi....

A functionalized derivative of the alpha 2-selective antagonist rauwolscine formed the basis for a photoaffinity adduct that has allowed identification of the hormone-binding subunit of the brain alpha 2-adrenergic receptor protein. Rauwolscine carboxylate underwent reaction with 4-N-t-butyloxycarbonyl-aminoaniline, leading to the synthesis of rauwolscine 4-aminophenyl carboxamide (Rau-AmPC). R...

The thalamus is the principal relay station of sensory information to the neocortex. In return, the neocortex sends a massive feedback projection back to the thalamus. The thalamus also receives neuromodulatory inputs from the brain stem reticular formation, which is vigorously activated during arousal. We investigated the effects of two neuromodulators, acetylcholine and norepinephrine, on cor...

We used a human platelet alpha 2-adrenergic receptor probe to study the tissue distribution and messenger RNA (mRNA) forms of the rat alpha 2-adrenergic receptor. Under stringent conditions of hybridization and washing, we detected an mRNA species of 3.8 kb. The abundance of this form follows the order spleen, kidney, brain stem and cortex, and skeletal muscle and lung and is consistent with th...

We studied the effects of alpha-adrenergic receptor stimulation and calcium on automaticity of isolated canine Purkinje fibers during simulated ischemia and reperfusion. Ischemia included acidosis (pH 6.7), hypoxia (PO2 = 10-25 mm Hg), hyperkalemia (10 mM K+), and either normal or elevated [Ca2+]o (2.7 or 10.8 mM). Control automatic rate and maximum diastolic potential were 18 +/- 2 beats/min a...

Chronic (3-day) treatment with prazosin causes an increase in renal alpha 2-adrenergic receptor density and the relocation of renal tubular alpha 2-adrenergic receptors from extrajunctional to postjunctional sites. We investigated whether chronic prazosin treatment (2 mg/kg, i.p.) caused a functional alteration of other renal alpha 2-adrenergic receptors, using the isolated perfused rat kidney....

Dobutamine and its stereoisomers were evaluated for alpha and beta adrenergic activities in vitro. The racemate and the (--)-isomer were found to be potent partial agonists of alpha adrenergic receptors in rat aorta. The (+)-isomer lacked alpha agonist activity. The affinities of (+/-)-, (+)- and (--)-dobutamine for the alpha adrenergic receptor were high (--log KB values of 7.01, 7.02 and 7.07...

PURPOSE To study the presence of muscarinic and alpha- and beta-adrenergic receptors in a normal human conjunctival epithelial (IOBA-NHC) cell line. METHODS Neurotransmitter receptors were determined in IOBA-NHC cells by flow cytometry, immunofluorescence, and Western blot analysis. Antibodies to M(1)-, M(2)-, and M(3)-muscarinic and to alpha(1A)-, alpha(1B)-, alpha(1D)-, alpha(2A)-, alpha(2B...