The concentration of cyclic AMP within cells is regulated by the activities of adenylyl cyclases and phosphodiesterases (PDE) and the receptors and G proteins that modulate their activities. The extent to which cyclic AMP accumulates in a given cell and activates protein kinase A (PKA) is subject to tight transcriptional and post-transcriptional autoregulation (Table 1). For example, cyclic AMP...

Adenosine is a ubiquitous neuromodulator that increases sleep, inhibits seizures, and promotes neuroprotection. Many of these effects are mediated by A1 receptors, but A1 receptors are expressed in most brain regions, and distinguishing the precise site of action of adenosine is challenging. To test the role of adenosine in different hippocampal regions, we have used the Cre-loxP system and an ...

A1 adenosine receptors from rat brain membranes were solubilized with the zwitterionic detergent 3-[3-( cholamidopropyl)dimeth ylammonio ]-1-propanesulfonate. The solubilized receptors retained all the characteristics of membrane-bound A1 adenosine receptors. A high and a low agonist affinity state for the radiolabelled agonist (R)-N'-eHJphenylisopropyladenosine((JH]PJA) with Kn values of 0.3 a...

The globus pallidus is a central nucleus in the basal ganglia motor control circuit. Morphological studies have revealed the expression of adenosine A2A receptors in the globus pallidus. To determine the modulation of adenosine A2A receptors on the activity of pallidal neurons in both normal and parkinsonian rats, in vivo electrophysiological and behavioral tests were performed in the present s...

BACKGROUND AND PURPOSE Adenosine A(3) receptors mediate beneficial effects in experimental colitis, but their involvement in enteric neuromuscular functions during bowel inflammation is undetermined. This study investigated the regulatory role of A(3) receptors on colonic motility in the presence of experimental colitis. EXPERIMENTAL APPROACH Colitis was induced in rats by 2,4-dinitrobenzenes...

Previous studies have shown that chronic salt loading increased renal interstitial adenosine concentrations and desensitized renal effects of adenosine, a phenomenon that could facilitate sodium excretion. However, the mechanisms responsible for the increased adenosine production and decreased adenosine response are poorly understood. This study examined the effects of the dietary high salt int...

There are multiple mechanisms by which adenine nucleotides can be released into the extracellular space in brain. Adenine nucleotides are converted extracellularly to adenosine, which then acts on adenosine receptors to elicit physiological responses, but the rate at which this conversion takes place is unknown. In the present experiments, adenine nucleotides were applied to individual hippocam...

Ever since the discovery of the hypotensive and bradycardiac effects of adenosine, adenosine receptors continue to represent promising drug targets. First, this is due to the fact that the receptors are expressed in a large variety of tissues. In particular, the actions of adenosine (or methylxanthine antagonists) in the central nervous system, in the circulation, on immune cells, and on other ...

Adenosine vasoconstricts preglomerular arterioles via adenosine A1 receptors. Because adenosine also activates adenosine A2 receptors, its overall renal vascular actions are complex and not fully understood. The present study was performed to determine the relative contributions of adenosine A1 and A2a receptors to the responsiveness of the renal microvasculature to adenosine. Afferent and effe...

The adenosine A3 receptor is expressed in brain, but the consequences of activation of this receptor on electrophysiological activity are unknown. We have characterized the actions of a selective adenosine A3 receptor agonist, 2-chloro-N6-(3-lodobenzyl)-adenosine-5'-N-methyluronamide (Cl-IB-MECA), and a selective A3 receptor antagonist, 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1, 4-(+...