In recent years topological indices are being developed to explain the pharmacological and toxic action of drugs at the molecular level. Using two newly formulated information theoretic topological indices, IC and SIC, a quantitative structure-activity relationship (QSAR) study has been carried out with three important series of bioactive agents : carbamoyl piperidines,barbiturates and alkanes. Statistical analysis reveals that IC and' SIC correlate significantly with the butyrylcholines-terase- inhibiting potency (Ki) of Carbamoyl piperidines, isohypnotic concentrations (c) of barbiturates and toxic doses (LD50) of alkanes. The study shows that these topological indices may be used for the prediction of the pharmacological and toxic action of molecules.

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The mechanism of direct vasodilator effect of thiazides was studied by using isolated strips prepared from rabbit aorta. All the thiazides caused relaxation of noradrenaline induced contraction but had no effect on the contractions produced by other smooth muscle stimulants. Thiazides per se did not block the effect of noradrenaline and their relaxant effect was not abolished by prior treatment with propranolol. It was absent in Ca2+ free Kreb's solution and was reversed by increasing the concentration of calcium. The probable mechanism of thiazide action appears to be an interferance with intracellular Ca2+ release by nor adrenaline.

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The effect of various minor tranquilisers, viz., diazepam, chlordia-zepoxide and meprobamate on the gastric acidity, was studied by continuous recording of acid gastric secretionin rats. All the drugs caused a statistically significant fall in the gastric pH. Atropine had a partial protective effect whereas chlorpheni- ramine alone or in combination with atropine had no effect on the fall in gastric pH caused by diazepam. Cimetidine completely blocked the action of diazepam on the gastric pH. Thus, the action of diazepam causing a fall in gastric pH of rats appears to be predominantly mediated through a histaminergic (H2-receptor mediated) machanism.

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The effects of phenformin and PGE, were studied on blood sugar, blood pressure and gastric acidity in cats when administered by intravenous and intracerebroventricular routes. PGE, reduced the blood pressure,blood sugar level and gastric acidity on intravenous administra-tion, while phenformin increased the blood pressure and blood sugar level but reduced gastric acidity. On intracerebroventricular administraion PGE, increased the blood pressure and blood sugar level but reduced the gastric acid while the action of phenformin on these parameters is diagnally opposite. It is suggested that the action of phenformin on the above parameters, may be due to inhibition of prostaglandin synthesis.

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A steroidal alkaloid with an additional-hydroxy and aminogroup was isolated from roots of Solanum giganteum Jacq (N. 0. Solanaceae). The compound decreased spontaneous motor activity and enhanced pentobarbitone hypnosis in albino mice. It produced spasmogenic responses on isolated smooth muscles like rat fundus and oestronised rat uterus and positive inotorpic effect on perfused frog's heart. Hypnotic potentiating effect in mice and spasmogenic responses on isolated smooth muscles were blocked by methysergide and BW501 C67 respectively suggesting that the compound possesses serotonin-like activity.

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PA2 and PA10 value of three. anticholinergic drugs i. e. atropine, oxyphenonium and diphenhydramine have been estimated on three isolated tissues of guineapig i. e. ileum, urinary bladder and vas deferens. The difference between pA2 and pA10 has been chosen as the criteria to establish the type of antagonism in different tissues with different drugs Antagonism seems to be of competitive nature in all tissues except Vas deferens with atropine.

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Hypothalamic 5-hydroxytryptamine (5-HT), dopamine (DA) and noradrenaline (NA) were estimated (from the same homogenate) in male wistar albino rats after different periods of immobilisation stress (IS). The rate of accumulation of these monoamines in the hypothalamus was also estimated after tranylcypromine pretreatment. There is an significant increase in the rate of synthesis of 5 HT between 30-60 min and that of DA between 15-30 min. The rate of synthesis of 5-HT decrease between 60-120 min and that of DA between 30-120 min. The is no significant change in the metabolism of hypothalamic NA. The results of the present study corroborate the earlier reported observation that early (0-30 min) and late (30-120 min) phase of S-induced hypothermia are primarily DA and 5-HT mediated.

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Effects of three trade preparations of insecticides viz. Tik 20, Diazone and Dalf-their active ingredients and their solvents present in the trade preparations, on skeletal muscle were studied in dogs and mice. Muscle paralysing effect was observed with various solvents. The clinical implications are discussed.

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Administration of acetazolamide (Diamox) during active gastric acid secretion is associated with transitory gastric mucosal glandular destruction and ulceration. The gastric mucosa recovers within 72 hours although functional capacity is known to be affected for several weeks following carbonic anhydrase inhibition.

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The effect of Sumithion an organophosphorus insecticide on growth rate, various internal organs, and cholinesterase enzyme activity has been studied in growing male rats at dietary levels of 200 and 500ppm for 80 days.There was a mortality of 46.6% (7/15) in the group on 500 ppm during the first three weeks and all the animals in this group exhibited cholinergic symptoms in the second and third week of feeding. The surviving animals were found to be normal. No such adverse effect was observed in the group maintained on 200 ppm Sumithion diet. Al. though the weekly growth rate was linear in both the groups, it was significantly depressed in 500 ppm dosed group but not in the group on 200 ppm diet. Cholinesterase enzyme activity was inhibited by 97% in the surviving animals maintained on 500 ppm. Sumithion diet, while the inhibition was 60% in the group on 200 ppm. Organ weights of liver, heart, lung, brain, kidney, adrenals, seminal vesicles and prostate in the experimental group were not significantly different from the control group and no gross pathological changes were observed.

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Intracerebroventricular administration of adrenaline, nor-adrenaline and phenylephrine through a chronically implanted cannula produced a fall followed by an after-rise in body temperature in guinea-pigs. Pretreatment with a-receptor antagonist tolazoline or phenoxybenzamine significantly reduced the hypothermia. Isoprenaline neither produced a significant fall in body temperature nor its slight hypothermic effect was blocked by propranolol. An involvement of central a-adrenoceptors in the production of catecholamine hypothermia in guinea-pig is suggested. The after-rise in temperature appears to be an unspecific fever.

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