The potential role of dimerization in controlling the expression and pharmacological properties of alpha1-adrenoceptor subtypes was examined using coimmunoprecipitation of epitope-tagged receptors. Human alpha1-adrenoceptor subtypes (alpha1A, alpha1B, alpha1D) were tagged at their amino-termini with Flag or hemagglutinin epitopes and transfected into human embryonic kidney 293 cells. Homodimeri...

Studies on mechanisms of desipramine (DMI) induced desensitization of the norepinephrine (NE) receptor coupled adenylate cyclase system in brain have shown that the endogenous agonist NE plays a pivotal role for both the development of subsensitivity and the down-regulation of beta adrenoceptors [l-4]. Moreover, an intact serotonergic neuronal input is co-required for the down-regulation of cen...

Previous studies have suggested that thyroid hormones influence the number of membrane-bound cardiac adrenoceptors, but their effect on the intracellular distribution of adrenoceptors has not been examined. A plasma cell membrane and a vesicular fraction devoid of membrane markers were prepared from hearts of euthyroid and hyperthyroid rats and were used to compare beta- and alpha-adrenoceptors...

Cigarette smoking is a putative environmental risk factor for colon cancer. Nicotine, an active alkaloid in tobacco, has been implicated in carcinogenesis. In the present study, we demonstrated that oral nicotine administration (50 or 200 microg/ml) for 25 days stimulated growth of human colon cancer xenograft in nude mice. It also increased vascularization in the tumors and elevated cotinine a...

The median preoptic nucleus (MnPO) in the lamina terminalis receives a prominent catecholaminergic innervation from the dorsomedial and ventrolateral medulla. The present investigation used whole cell patch-clamp recordings in rat brain slice preparations to evaluate the hypothesis that presynaptic adrenoceptors could modulate GABAergic inputs to MnPO neurons. Bath applications of norepinephrin...

Stress has emerged as a factor associated with cardiovascular disease. Catecholamines released during the stress reaction by sympathetic nerves and adrenal medulla couple to β1-and β2-adrenoceptors in cardiomyocytes membrane enhancing heart function order attend organism demand. This might produce excessive reactive oxygen species what may culminate oxidative progression of several cardiac dise...

1. The aim of the investigation was to determine whether the adrenoceptors of the chick rectum preparation complied with Ahlquist's classification; phentolamine (0.1 mug/ml) and propranolol (0.05 mug/ml) were used as specific antagonists of alpha- and beta-adrenoceptors, respectively.2. Propranolol antagonized phenylephrine, isoprenaline and noradrenaline in the chick rectum preparation, althou...

There is convincing evidence to suggest that there are direct effects of adrenergic agents on renal tubules. During the last several years, considerable progress has been made in determining the type of adrenoceptors present in renal tubular cells through the use of radioligand binding and signal transduction methods. The receptor data are summarized in table 6. Almost all major nephron segment...

β(3)-Adrenoceptors have been demonstrated to mediate urinary bladder smooth muscle relaxation but proof of their expression at the protein level has been missing because of lack of suitable antibodies or radioligands. As among various available radioligands [(125)I]-iodocyanopindolol ([(125)I]-ICYP) exhibited the smallest problems in labeling cloned human β(3)-adrenoceptors in previous studies,...