Repeated administrations of clonidine to spontaneously hypertensive rats (SHR) markedly lowered dopamine β-hydroxylase (DBH) activity in the locus coeruleus (LC) and increased it in the spinal intermediolateral cell column (IML), while α-methyldopa tended to lower the enzyme activity in the medullary nucleus tractus solitarii (NTS) and Al cell areas. Clonidine-induced inhibition of ³H-norepinephrine binding to crude cerebral membranes of SHR or Kyoto Wistar rats (KWR) as a measure of α-receptor agonist activity was 7 times greater than that of (±) a-methyl- (±) -norepin-ephrine. Clonidine and hydralazine significantly lowered phenylethanolamine N-methyltransferase (PNMT) activity elevated in the nucleus hypothalamicus posterior (NHP) of SHR to the level of KWR, and both drugs or α-methyldopa consistently increased PNMT in the nucleus paraventricularis (NPA). Peripherally active hydralazine also increased PNMT activity in the NTS, and antagonized the activity elevated in the Al cell area of SHR to the level of KWR. In conclusion, clonidine selectively lowers DBH activity in the LC, while α-methyldopa appears to decrease the enzyme activity in the medullary NTS and Al cell areas, suggesting different sites of action of both drugs. The decreased DBH activity in these nuclei may be related to stimulation of respective α-noradrenergic receptors. Elevating effects of all three drugs on PNMT activity in the NPA may be due to decreased baroreceptor afferent impulses to the nucleus after a fall in blood pressure.

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The effects of various salts on the activity of mitochondrial monoamine oxidase (MAO) from bovine liver were studied by measuring the initial and long-term enzyme reactions with an oxygen electrode and Warburg's manometer, respectively, using several monoamines as substrates. Salts with a _-Cl^- group, such as KCl and NaCl, or with a _-NO₃^- group, such as KNO₃ and NaNO₃, increased the initial MAO activity with tyramine as substrate. NaCl strongly inhibited the long-term enzyme reaction. With tyramine as substrate, NaCl increased the activity only during the first 6 to 7 min of the reaction. Similarly with β-phenylethylamine or butylamine as substrate, NaCl increased the initial MAO activity, but decreased the activity in the long-term reaction. On the other hand, with serotonin or benzylamine as substrate, NaCl decreased both the initial reaction and the long-term reaction. The effect of NaCl on the enzyme with tyramine as substrate was reversible, while with serotonin as substrate it was irreversible. These results indicate that the effect of NaCl depends on the substrate used and suggest that bovine liver mitochondria contain at least two different forms of MAO.

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The mechanism of actions of L-ascorbic acid (AA) on the guinea pig isolated ileum was studied. AA (neutralized, 10^-3 M) produced a stimulated motility (A effect) and a potentiation in acetylcholine (ACh) -induced contraction (B effect). The A effect showed a tachyphylaxis, and was inhibited by tetrodotoxin, atropine, adenosine, morphine, strychnine, Mg²⁺, papaverine and glucose- and Ca²⁺-free medium, but was stimulated by eserine. Thus, AA appears to have not only a direct myogenic effect but also a neurogenic effect by stimulating ACh release from intramural cholinergic nerves.

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Studies were carried out to elucidate the mechanism of action of chlorphenesin carbamate (CPC) and to compare the effect of the drug with that of mephenesin on the isolated bullfrog spinal cord. Ventral and dorsal root potentials were recorded by means of the sucrose-gap method. CPC caused marked hyperpolarizations and depressed spontaneous activities in both of the primary afferent terminals (PAT) and motoneurons (MN). These hyperpolarizations were observed even in high-Mg²⁺ and Ca²⁺-free Ringer's solution, suggesting that CPC has direct actions on PAT and MN. Various reflex potentials (dorsal and ventral root potentials elicited by stimulating dorsal and ventral root, respectively) tended to be depressed by CPC as well as by mephenesin. Excitatory amino acids (L-aspartic acid and L-glutamic acid) caused marked depolarizations in PAT and MN, and increased the firing rate in MN. CPC did not modify the depolarization but abolished the motoneuron firing induced by these amino acids. However, mephenesin reduced both the depolarization and the motoneuron firing. The dorsal and ventral root potentials evoked by tetanic stimulation (40 Hz) of the dorsal root were depressed by the drugs. These results indicate that CPC has an apparent depressing action on the spinal neuron, and this action may be ascribed to the slight hyperpolarization and/or the prolongation of refractory period.

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The metabolic fate of a new antiallergic agent, azelastine (4- (p-chlorobenzyl) - 2- [N-methylperhydroazepinyl- (4)] -1- (2H) -phthalazinone hydrochloride) in rats and guinea pigs was investigated using its ¹⁴C-labelled compound. The blood level of radioactivity reached the maximum at 1-1.5 hr after oral administration, indicating the rapid absorption of the drug from gastrointestinal tract. A high concentration of radioactivity was detected in the lung of both species following either oral or intravenous administration. The major pathway of excretion of radioactivity was by way into feces, in both species. The radioactivity excreted in feces was attributable to that which was excreted in bile and exsorbed into gastrointegtinal tract. When the drug was given to pregnant rats, the concentration of radioactivity in the fetus was significantly lower than those in placenta and uterus, indicating the limited placental transfer of the drug. The successive oral administration of the drug in lower doses exerted no effect on the activity of microsomal drug-metabolizing enzymes of rat liver, while in higher doses, had a slight effect.

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A new scale for the potentiation was introduced and was termed pA_1/2. The value can be calculated by using an equation ; pA_1/2=pAx + log (1/x-1), which is similar to that which is used for the calculation of pA₂. For the use of the equation, the parallel shift of the dose-response curve and the unchanged maximum response are prerequisites. This experiment showed the validity and the usefulness of calculating the pA_1/2 values, in the biological assay. In the assay of anticholinesterases, the potentiating effects of neostigmine or physostigmine on the acetylcholine-induced contraction were examined, by using frog's rectus abdominis. The pA_1/2 values obtained in the presence of two different concentrations of anticholinesterases were the same, indicating that pA_1/2 is a parameter which is specific to the potentiator. The potentiating effects of some cardenolides on the K-induced contracture were examined, by using the frog's ventricular muscles. The relative potencies of four cardenolides obtained from the pA_1/2 values well agreed with those reported earlier. The amount of the cardenolides required for this assay was smaller than required for other methods.

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Intragastric administration of a Chinese herb, Huang Chin extract (Scutellaria baicalensis George), produced a dose-dependent fall in rectal temperature in conscious rats in a room the temperature of which was 22°C or below. The hypothermia in response to Huang Chin application was brought about solely by cutaneous vasodilatation (as estimated by an increase in cutaneous temperatures). There were no changes in either metabolic heat production or respiratory evaporative heat loss. However, in the heat (29°C), Huang Chin administration produced no changes in rectal temperature or other thermoregulatory responses. The data indicate that Huang Chin extract produces peripheral vasodilatation which leads to a hypothermia in conscious rats.

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Effects of Phthalazinol (EG 626), a cyclic AMP phosphodiesterase inhibitor, a thromboxane A2 antagonist and an antiatherosclerotic agent was examined regarding lipolytic enzyme activities in rat epididymal adipose tissue. The effect of Pyridinol-carbamate (Anginin) was concomitantly examined. There was a significant decrease in serum triacylglycerol levels in rats given EG 626 (100-500 mg/kg), p.o. for 1-3 weeks. In adipose tissue from EG 626 treated rats, the basal and adrenalin induced lipolysis, and cholesterylester hydrolase activity were markedly enhanced, while the phosphodiesterase activity was decreased. Anginin treatment had no effect either on the serum lipid levels or the cholesterylester hydrolase activity. An elevation in cholesterylester hydrolase activity and lipolysis by EG 626 was observed both in vivo and in vitro. Incubation of the adipose tissue with 0.229 mM of EG 626 or 0.603 mM of theophylline induced a lipolysis equivalent to that seen with 2.7×10^-2 mM of adrenalin. These results indicate that EG 626 exerted marked effects on lipolysis and cholesterylester hydrolase activity, probably through inhibition of phosphodiesterase. Possible contributions of the enhanced cholesterylester hydrolase activities to the antiatherogenic effect were discussed.

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We have examined the effect of dietary protein deficiency on rat hepatic drug-metabolizing enzyme system for a period of two months. Cytochrome P-450 and b5 contents in liver microsomes, which were plotted on semilogarithmic paper as a function of the time of deficiency, showed biphasical reductions during protein deficiency : rapid decreases in the first 3 weeks were followed by more gradual decreases. However, the three enzymatic activities examined, i.e. aminopyrine demethylase, aniline hydroxylase and p-nitroanisole demethylase, were not reduced at a uniform rate. In the earlier phase, activities of the former two enzymes were reduced more rapidly than that of the last phase. This biphasical and non-uniform reduction of enzymatic activities suggests the existence of two or more cytochrome P-450 subspecies in non-depleted male rats. Intraperitoneal administration of well-known environmental pollutants, polychlorinated dibenzofurans and biphenyls (100 μg and 100 mg/kg, respectively) to the depleted rats resulted in a marked induction of drug-metabolizing enzymes. However, as the deficiency became more severe (2 months), the induction declined to a considerable degree, especially in the case of polychlorinated biphenyl administration.

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Butylidenephthalide (BdPh), ligustilide and butylphthalide were isolated and purified from neutral oil of Ligusticum wallichii Franch. Among these three, BdPh proved to be the most active in inhibiting rat uterine contractions induced by prostaglandin F_2a, oxytocin and ACh. In studies done to compare the effects of BdPh and papaverine (Pap), guinea pig ileum, was deferens and taenia coli were used. BdPh inhibited contractile responses of the ileum to agonists including ACh, K⁺ and Ba²⁺ in normal Tyrode solution and to exogenous Ca²⁺ in high K⁺ (80 mM), Ca2⁺-free Tyrode solution, and also responses of was deferens responses to norepinephrine. Thus, BdPh is a non-specific antispasmodic but weaker in potency than Pap. However, as the inhibitory effects of BdPh on phasic contraction (PC) and tonic contraction (TC) of preparations, including depolarized and non-depolarized ileum and taenia coli, were much the same, it is suggested that the action mechanism of BdPh may differ from that of Pap which inhibited TC more selectively than PC. It may be concluded that BdPh possesses an non-specific antispasmodic action like Pap, the mechanism of action being different from that of Pap.

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Ninety-two mice were divided into 2 groups and 2.5 mg/kg of d-amphetamine sulfate was given to one group, and 10 mg/kg of morphine hydrochloride to the other, at daily intervals. These two groups were then futher divided into flicking light-presented and non-presented groups. The acute effects of the drugs on the ambulatory activity of each mouse were observed for 180 min after the drug administration. The motor-accelerating effect of both drugs was progressively enhanced with repeated administration. After the drugs were administered 10 times, physiological saline was given subcutaneously to the mice and the motor-accelerating effect of the drugs could be observed for a short time, especially in the flicking light-presented groups. This effect disappeared after repeated administration of saline solution at daily intervals for 6 days. Thus, the motor-accelerating effect produced by saline is considered to have been elicited as the result of conditioning between the conditioned stimuli (flicking light and other environmental factors) and drug effects.

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When dextran ³⁵S-sulfates (DSs), anticoagulants and antilipemic agents, were intravenously given to rats, the specific radioactivity was five to twenty times higher in the lysosomal than in the other subcellular fractions of liver, but the counts in this fraction were only 10% of total radioactivity distributed to the liver. Therefore, we investigated the biliary excretion of ³⁵S-DSs with a similar sulfur content of 18% and three different average molecular weights (AMW) of 3000, 20, 000, and 200, 000. The excretion rate was about 2 % of the radioactivity given, per hour, after intravenous administration of³⁵S-DS with AMW of 20, 000, 10 mg/kg. At this time, acid phosphatase activity and calcium content of bile also were increased, and well correlated with the amount of the radioactivity excreted to bile. The amount of the radioactivity distributed to the lysosomal fraction is correlated with the enhanced activities of Na⁺- K⁺-dependent and Ca²⁺-activated ATPase in this fraction, indexes of endocytotic and exocytotic transports. DSs significantly enhanced ⁴⁵Ca levels of the lysosomal, but not the cytosol fraction when ⁴⁵CaCl₂ was given alone or simultaneously with DSs. According to our previous reports that DSs are transferred to the lysosomal fraction of liver and intestinal mucosa by endocytosis, the present results suggest that DSs, especially with high AMW and which are distributed to liver lysosomes are rapidly excreted into bile by exocytosis and accompanied by calcium and lysosomal enzymes.

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