Effectiveness of E-643, a newly developed alpha-blocker, and four alpha-antagonists in blocking pre- and postsynaptic alpha-adrenoceptors were compared in the isolated rat vas deferens. The inhibitory effect of clonidine on the field-stimulated twitch response was antagonized in the presence of the alpha-antagonist. The order of affinity (pA2) for presynaptic alpha-receptors, as assessed from p...

It is known that moxonidine acts as an agonist at presynaptic 2-adrenoceptors of the postganglionic sympathetic nerve terminals and leads to a reduction in noradrenaline release. In addition, it is conceivable that I1-binding sites located in other regions of the preand postganglionic sympathetic neurons are involved in this effect. Our aim was to investigate whether and to what extent activati...

The effect of clonidine (average 0.24 mg/day) and propranolol (average 105 mg/day) on home blood pressure readings in 16 patients with borderline hypertension was investigated in a randomized, double-blind, placebo crossover design. Patients could detect small but significant decreases of blood pressure with both active compounds (-8/-5 with propranolol and -11/-7 with clonidine). The larger me...

In the title compound, guanidinium chloridotrioxidochrom-ate(VI), (CH(6)N(3))[CrClO(3)], both the cation and anion are generated by crystallographic mirror symmetry, with one O and one N atom and the Cr, Cl and C atoms lying on the mirror plane. The bond lengths in the guanidinium cation are inter-mediate between normal C-N and C=N bond lengths, indicating significant delocalization in this spe...

Schedule-controlled responding was maintained under multiple fixed-interval, fixed-ratio schedules in pigeons and single fixed-ratio schedules in mice. In pigeons, clonidine, an alpha 2-receptor agonist, produced dose-related decreases in responding under both fixed-interval and fixed-ratio schedules; fixed-interval responding was decreased at a lower dose than fixed-ratio responding. Low to in...

Imidazole-4-acetic acid-ribotide (IAA-RP), an endogenous agonist at imidazoline receptors (I-Rs), is a putative neurotransmitter/regulator in mammalian brain. We studied the effects of IAA-RP on excitatory transmission by performing extracellular and whole cell recordings at Schaffer collateral-CA1 synapses in rat hippocampal slices. Bath-applied IAA-RP induced a concentration-dependent depress...

We previously reported that serine/threonine protein phosphatases (PPs) play a role in the antinociception induced by the mu-opioid receptor agonist morphine. In this study we evaluated the possible involvement of PPs on the antinociception induced by agonists of others G protein-coupled receptors in the tail flick test in mice. The subcutaneous administration of clonidine (0.25-4 mg/kg), baclo...