The human genome encodes nine different adrenoceptor genes. These are grouped into three families, namely, the α1-, α2-, and β-adrenoceptors, with three family members each. Adrenoceptors are expressed by most cell types of the human body and are primary targets of the catecholamines epinephrine and norepinephrine that are released from the sympathetic nervous system during its activation. Upon...

We examined the down-regulation of alpha-1B adrenoceptors in Madin-Darby canine kidney D1 (MDCK) cells with an emphasis on a possible role of protein kinase C. The alpha-1 adrenoceptor agonist phenylephrine (1-100 microM) concentration-dependently down-regulated alpha-1B adrenoceptors in MDCK cells. Down-regulation by 100 microM phenylephrine was detectable after 2 hr and maximal after 8 to 24 ...

The mechanism through which the repartitioning agent clenbuterol increases heart rate was investigated. First, the relative importance of the beta 1- and beta 2-adrenoceptors was established in rat and bovine right atria in vitro. The positive chronotropic and inotropic effects of (+/-)isoproterenol in rat and bovine right atria, respectively, were markedly antagonized (P < .001) by the beta 1-...

The lateral septal area (LSA) is a limbic structure involved in autonomic, neuroendocrine and behavioural responses. An inhibitory influence of the LSA on baroreflex activity has been reported; however, the local neurotransmitter involved in this modulation is still unclear. In the present study, we verified the involvement of local LSA adrenoceptors in modulating cardiac baroreflex activity in...

Functional role of endothelial alpha(2)-adrenoceptor in coronary circulation remains unclear. Clonidine, an agonist of alpha(2)-adrenoceptors, was reported to induce coronary vasodilatation via stimulation of endothelial alpha(2)-adrenoceptors or coronary vasoconstriction involving vascular smooth muscle alpha(2)-adrenoceptors. Moreover, H(2) receptor-dependent responses to clonidine were descr...

On the basis of data obtained in rabbits, the imidazoline receptor ligand rilmenidine has been suggested to decrease blood pressure in humans by activating central a2A-adrenoceptors. A prerequisite for this hypothesis was the unproved assumption that rabbit and human a2A-adrenoceptors are equally activated by rilmenidine. Because a2A-adrenoceptors in the brain and on cardiovascular sympathetic ...

We wanted to determine which alpha-adrenoceptor subtypes mediate phenylephrine (PE) contraction of dog mesenteric artery in vitro. We studied antagonisms in response to prazosin, 2-(2, 6-dimethoxyphenoxyethyl)-aminomethyl-1,4-benzodioxane, 5-methylurapidil, N-[2-(2-cyclopropyl methoxy phenoxy)ethyl]5-chloro-alpha,alpha-dimethyl-1H-indole-3-ethanamine HCl (RS 17053), 8-3-[4-(2-methoxyphenyl)-1-p...

Cigarette smoke is a risk factor for esophageal squamous cell carcinoma (ESCC). It contains several carcinogens known to initiate and promote tumorigenesis as well as metastasis. The nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is one of the strongest carcinogens in tobacco and our previous studies have shown its proliferation-promoting role in the progression of ESCC. Recen...

The insular cortex (IC) is a limbic structure involved in cardiovascular responses observed during aversive threats. However, the specific neurotransmitter mediating IC control of cardiovascular adjustments to stress is yet unknown. Therefore, in the present study we investigated the role of local IC adrenoceptors in the cardiovascular responses elicited by acute restraint stress in rats. Bilat...

The aim of this study was to explore the cellular mechanisms underlying the impaired contractile response to beta adrenoceptor stimulation in diabetic hearts. Chronic diabetes was induced in rats by a streptozotocin injection. Four to six weeks later, papillary muscles isolated from diabetic hearts exhibited marked reductions in the positive inotropic responses to isoproterenol, norepinephrine ...