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A number of quaternary bases were tested for their ability to inhibit the synthesis of acetylcholine (ACh) by incubated minced mouse brain. Tetramethyl-, tetraethyl-, tetrapropyl-, and tetrabutyl-ammonium were moderately active as inhibitors, the strongest being the tetraethyl base (TEA), which was 1–2% as active as the hemicholinium HC-3. Weaker activity was exhibited by hexamethonium, d-tubocurarine, and tolazoline; NH4Cl and N-methylnicotinamide were inactive at concentrations up to 10−2 M. Except in high concentrations, none of the bases significantly affected the release of ACh from the tissue into the eserinized medium. The addition of choline to the medium somewhat increased the rate of ACh formation when the bases were absent and strikingly antagonized the inhibitory action of HC-3 and TEA. TEA also resembled HC-3 in that (i) it reduced the ACh content of the preganglionically excited superior cervical ganglion of the cat, though neither stimulation alone nor the drug alone has such an effect; (ii) it killed mice by paralyzing respiration, and this effect was antagonized by choline; (iii) its inhibitory effect on ACh synthesis by intact nervous tissue was not due to direct inhibition of choline acetylase. The finding of Birks and Quastel that extracellular Na+is essential for the synthesis and storage of ACh by perfused sympathetic ganglia was confirmed for incubated brain tissue. Neither the action of HC-3 and TEA in inhibiting ACh synthesis, nor that of Na+in promoting it, has as yet been clarified.

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Viscum angulatum Heyne ex DC (Viscaceae) is a leafless hemiparasitic shrub traditionally used in Asian countries for the treatment of hypertension. In the present study, the methanol extract of the whole plant was examined for diuretic activity in rats. The activity was evaluated using parameters such as urine volume after 5, 19, and 24 h and urine sodium, potassium, and chloride concentrations. The extract was further scrutinized for polyphenolic compounds and triterpenoids. The extract demonstrated a significant increase in and dose-dependent effect on urine excretion volume in comparison to the normal group in the tested range of 100-400 mg/kg. The extract demonstrated comparable saluretic and higher natriuretic activity (Na(+)/K(+)) compared to the furosemide treated group. However, the Cl(-)/Na(+) + K(+) ratio, which indicates carbonic anhydrase mediated activity, remained unaffected. HPLC and quantitative analysis of the extract revealed that polyphenolic compounds and the triterpenoid, oleanolic acid, are the major phytochemicals, and are proposed to be responsible for the observed diuretic effect. Oleanolic acid has been reported to possess diuretic activity with significant potassium loss in rats. In contrast to pure oleanolic acid, the extract demonstrated a valuable potassium-sparing effect. This suggests modulation of the diuretic effect of oleanolic acid by polyphenolics present in the extract. The observed dose-dependent potassium-sparing diuretic effect is a hereto unreported property of this plant.

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