Noradrenaline uptake mechanisms in human atrium

Sympathomimetic effects of Parquetina nigrescens (Periplocaceae) extract in isolated portal vein smooth muscle

The purpose of this study was to examine the mechanisms underlying the pharmacological effects of the extract of Parquetina nigrescens (Expar) on vascular smooth muscle contractility. To evaluate the Expar effect, the contractile activity of portal veins isolated from Wistar Kyoto rats was isometrically recorded. Isolated portal vein preparations developed rhythmic and spontaneous contractile activity. Expar increased the contractile response of the portal vein preparations in a dose-dependent manner. The maximal effect of the dose-response curve for Expar was prevented by the alpha1-adrenergic blocking agent prazosin at 10 nM and 30 nM concentration dependently. The contractile responses of the muscle to Expar were partly blocked after chemical sympathectomy of the preparations with 6-hydroxydopamine, and those obtained in the same conditions with tyramine were completely abolished, whereas responses to noradrenaline were unaffected by the 6-hydroxydopamine pretreatment. It is concluded that Expar contains principles, which can be characterized as direct and indirect sympathomimetic.

Uptake of noradrenaline in high altitude native's heart

Uptake of 3H-noradrenaline by the heart was studied with sections of isolated atria obtained from high or lowlanders. In native highlanders, affinity for 3H-noradrenaline by human atria is more significant than in lowlanders. Furthermore, the Michaelis Menten constant is lower in high altitude native's heart.

Neurochemical characterization of a new potent and selective serotonin uptake inhibitor: Lu 10-171

The neurochemical characteristics of a new bicyclic phthalane derivative-Lu10-171 [1-(3-(dimethylamino)propyl)-1-(p-fluorophenyl)-5-phthalancarbonitrile; citalopram]-have been investigated. Lu 10-171 and its metabolites were compared with tricyclic thymoleptics in several tests for serotonin (5-HT),noradrenaline (NA), and dopamine (DA) uptake inhibiton in vitro and in vivo. Lu 10-171 is a very potent and completely selective inhibitor of the 5-HT reuptake mechanism, being 2-10 times as active as chlorimipramine. The metabolites of Lu 10-171 show weak 5-HT uptake inhibiting properties. Lu10-171 and its metabolites are devoid of NA uptake inhibiting properties and in this respect they clearly differ from the tricyclic antidepressants, which posses effects both on 5-HT and NA uptake. The inhibition of 5-HT uptake in vitro is competitive and not connected with an increased efflux of 5-HT. Lu10-171 and its metabolites only inhibit DA uptake in extremely high concentrations and in this respect they are even weaker than chlorimipramine and other tricyclic thymoleptics. Like the tricycle thymoleptics, Lu 10-171 is without effect on MAO and does not change the endogenous levels of brain monoamines. Due to the selective action on 5-HT uptake, Lu 10-171 seems to be a valuable tool in studying the role of central 5-HT neurone systems in experimental neuropharmacology as well as in the ethiology of depressive illness.

Comparative studies of a new 5HT-uptake inhibitor and some tricyclic thymoleptics

The new 5HT-uptake inhibitor, FG 4963, and some tricyclic thymoleptics antagonized p-chloroamphetamine (PCA)-induced hypermotility in rats. FG 4963 was active in about the same s.c. and p.o. doses as chlorimipramine. FG 4963, imipramine and chlorimipramine potentiated hypermotility induced in mice by the 5HT precursor 5HTP, FG 4963 being slighly more active than chlorimipramine. In contrast to the tricyclic thymoleptics FG 4963 did not potentiate the heart rate increasing effect of NA in pithed rats. The peripheral anticholinergic effect of FG 4963 and of desipramine was almost identical while the other imipramine derivatives were more active. All tricyclic thymoleptics were strong peripheral antihistaminics, but FG 4963 was almost devoid of this action. Acute tests for ECG changes in guinea pigs and toxicity in mice and rats showed that FG 4963 and chlorimipramine were less toxic than imipramine and amitriptyline. FG 4963 is presumably a selective 5HT-uptake inhibitor producing much less potentiation of peripheral sympathetic mechanisms than do the tricyclic antidepressants.

Neurochemical and pharmacological studies on a new 5HT-uptake inhibitor, FG4963, with potential antidepressant properties

A new phenylpiperidine derivative, FG4963, and several tricyclic antidepressants were compared in various in vitro and in vivo tests for central 5HT- and NA-uptake inhibition. FG4963 was found to be a 5HT-pump blocker with activity similar to that of chlorimipramine. FG4963 inhibited NA-uptake less than the most potent tricyclic thymoleptics. In contrast to imipramine derivatives FG4963 was a weak inhibitor of peripheral NA-uptake. FG4963 seems to produce central 5HT-potentiation without affecting organ functions regulated by the autonomic nervous system as much as tricyclic antidepressants.