Using Scatchard plots, high and low affinity Ca binding sites were detected on the surface membrane of vascular smooth muscle. Superficial low affinity bound Ca was rapidly lost in Ca-depleted solution and K-induced contraction appears to depend upon this Ca source. A part of this low affinity bound Ca exchanged slowly and was rapidly released by norepinephrine. Superficial high affinity bound Ca was not readily lost in Ca-depleted solution and was removed by La and EGTA, suggesting that the sustained contraction induced by norepinephrine may be supported by this Ca component. The La-inaccessible (cellular) Ca was also separated into high and low affinity bound Ca. Cellular low affinity bound Ca increased in high-K solution but not by norepinephrine. In depolarized muscle, however, norepinephrine increased the cellular low affinity bound Ca. Inhibitors of mitochondrial respiration inhibited Ca binding to the cellular low affinity binding site but not the K-induced contraction, suggesting that this Ca component represents mitochondrial Ca uptake. Cellular high affinity binding site took up Ca slowly and the bound Ca was released rapidly by norepinephrine. This source of Ca may be utilized for norepinephrine-induced phasic contraction.

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The antipyretic effects of aminopyrine and sodium acetylsalicylate on endotoxin-induced fever in rabbits were studied relative to the route and dose of administration. Intravenous administration of aminopyrine produced a marked antipyretic effect, intracisternal administration produced a lesser effect and i.v. was the effective route. Similar results were obtained in the nonfebrile rabbits. On the contrary, the intracisternal administration of sodium acetylsalicylate reduced the body temperature to the same degree both in febrile and nonfebrile rabbits, but sodium acetylsalicylate given i.v. to nonfebrile rabbits did not reduce the body temperature. 4-aminoantipyrine and N-acetyl-4-aminoantipyrine, the major metabolites of aminopyrine had a lesser effect in the febrile rabbits. Antipyretic effects of sodium salicylate, the metabolite of sodium acetylsalicylate were similar to the effects of sodium acetylsalicylate. These data suggest that the antipyretic effects of aminopyrine may not be involved in the CNS, while the antipyretic effects of salicylate may be due to a direct action on the CNS.

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In attempts to study drug-induced auditory impairment we measured the auditory threshold in rats, using the shuttle box method. The auditory threshold with physical impairment of ears was also measured. The sensitivity of the rats to the auditory response was decreased to about 15dB in cotton-stuffed ears and to about 20dB in pierced eardrums. In this experiment, we used drugs known to be ototoxic; dihydrostreptomycin sulfate, kanamycin sulfate, neomycin sulfate and ethacrynic acid. With successive administration of each drug, the auditory sensitivity in rats decreased. This shuttle box method is easily facilitated and the auditory threshold of many rats can be measured over a short period. This approach may be a useful method for screening ototoxic drugs.

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Two types of phenothiazinic anti-inflammatory agents, protizinic acid (PZA) and metiazinic acid (MZA) were examined using 1) heat denaturation test, 2) heat-induced erythrocyte lysis, 3) several platelet functions, 4) model membrane systems containing the same phospholipids and cholesterol compositions as in platelets. PZA and MZA were inhibited with heat denaturation in a similar manner seen with BSA and heat-induced erythrocyte lysis, and effects were more potent than indomethacin (IM). PZA showed inhibitory effects similar to MZA on ADP or collagen-induced platelet aggregation. However, in arachidonic acid (AA)-induced rabbit platelet aggregation, PZA had a more potent effect, similar to effects seen with IM and more potent than those of MZA. PZA inhibited the lethal effect of AA in rabbits at concentrations lower then MZA. To determine the sites of action, we examined the effects on uptake and release reactions of ³H-serotonin. PZA and MZA did not affect the uptake reaction but did reduce the release of serotonin to a greater extent than seen with IM. The tested drugs had little effect on the platelet aggregation in vivo. To investigate the interaction of these drugs with lipid bilayers, we used liposomes as a model membrane, of which the lipids compositions were the same as that of platelets. The tested drugs showed inhibitions of the liposome aggregation with addition of 6 mM Ca²⁺, in a dose dependent manner and similar to findings in the drug-platelet system. In this experiment, PZA had a more potent interaction with lipid bilayers than did MZA. These results suggest that interactions of PZA with the platelet membrane may be the origin of the PZA-induced inhibition of the platelet aggregation, in addition to the effect on the biosynthesis of prostaglandins.

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Effects of budralazine, a new antihypertensive drug, on regional circulation in various sites of brain and extracranial skeletal muscle and skin in curarized, artificially respirated cats were studied using the thermoelectrical method. Budralazine produced an increase in blood flow in the cerebral cortex and hippocampus. Effects of the drug on blood flow in the hypothalamus and amygdala were inconsistent. Budralazine produced an apparent increase in muscular blood flow, whereas the drug did not consistently alter dermal blood flow. Budralazine produced a mild and sustained fall in blood pressure, particularly after the repeated administration. Thus, the action of budralazine seems to be mainly one of a smooth muscle relaxant effect. The mode of action of the drug seems to differ from that of papaverine or hydralazine.

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Effects of diltiazem (Dil) on cardiac function were studied in the anesthetized open chest and heart-lung preparation of dogs. In the anesthetized dog, Dil (0.03 ?? 0.3 mg/kg, i.v.) increased max dp/dt and raised left ventricular end-diastolic pressure (LVEDP). Dil also produced an increase in cardiac output and coronary blood flow, but produced a decrease in blood pressure and heart rate (HR). In the cardiac denervated dog (bilateral stellectomy and vagotomy), the increase in max dp/dt caused by Dil, although not so remarkable was apparent. Therefore, the effects of Dil on cardiac function were examined in the heart-lung preparations of the dog, in which arterial pressure (AP) and venous pressure (VP) were kept constant (spontaneously beating) or AP, VP and HR were kept constant (atrial pacing). In these preparations Dil (about 1 mg/l) decreased max dp/dt and raised LVEDP. The cardiac function curve (relationship between stroke work and LVEDP) was shifted rightward by Dil. On the other hand, max dp/dt was increased when VP was increased under constant AP and HR. This increase in max dp/dt was also found under the influence of Dil. These results suggest that the augmentation of max dp/dt induced by Dil in the open chest dog is due both to a neural reflex in response to the systemic hypotension and to the Starling mechanism produced by increase in venous return, though Dil itself has a negative inotropic property.

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Gastrosecretory effects of intravenous administration, and microinjection and electro-osmotic application into the lateral hypothalamus (LHA) were investigated in the case of bombesin, alone and concomitant administration with insulin or 2-deoxy-D-glucose (2-DG). Bombesin, a tetradecapeptide found in the brain and gastrointestinal tract of mammals, is a potent gastrin releasing factor. At doses below the threshold of gastric secretion, bombesin produced a decrease in latency and an increase in the amount of insulin-induced gastric acid secretion. In the LHA, microinjections and electro-osmotic applications had similar effects but did not affect secretion when given alone, yet reduced the latency and increased the amount of insulin-induced acid secretion. LHA neuronal activity was also unaffected by electro-osmotic application of bombesin alone, but this compound enhanced the excitatory effects of both insulin and/or 2-DG. Thus, the gastric secretory effects of bombesin appear to be local. This peptide modulates LHA-gastrosecretory mechanism but it is ineffective when administered alone.

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The anti-inflammatory activity of dexamethasone 17-valerate ointment (DV-17, 0.12%) was investigated by topical application in mice and rats, and the effects compared with those of dexamethasone (DX, 0.12%), betamethasone 17-valerate (BV-17, 0.12%), beclomethasone 17, 21-dipropionate (BE, 0.025%) and hydrocortisone 17-butyrate (HC, 0.1%) which were prepared with the same ointment base. DV-17 inhibited markedly the superficial inflammation such as increased vascular permeability induced by intradermal injection of histamine or bradykinin in rats and edema induced by a drop of croton oil into the mouse ear. DV-17 also inhibited significantly rat paw edema induced by carrageenin, yeast, nystatin and mustard. The inhibitory activity of DV-17 on those acute inflammatory responses was similar to that of DX and BV-17. In the inhibitory activity on carrageenin induced paw edema, DV-17 was less potent than that of DX when given orally, however was similar to DX in topical application. DV-17 also inhibited granulation tissue proliferation by subcutaneous paper disk implantation and nontreated foot swelling in adjuvant arthritic rats, but the inhibitory activity of DV-17 on the inflammation of these distant areas was lower than that of DX. On the other hand, systemic effects such as decrease in weight of adrenal or thymus and body weight loss were most evident in the case of DX and lower with DV-17. DV-17 prolonged wound healing and inhibited the delayed-type hypersensitivity induced by picryl chloride. The activity was equivalent to that of DX and BV-17. From the above results, it may be considered that DV-17 possesses potent anti-inflammatory activity, whereas it has fewer side effects and is a useful glucocorticoid for external application.

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Pharmacological activities of HSR-902, a new antispasmodic agent, in gastrointestinal tract, biliary and urinary systems were compared with those of atropine, butylscopolamine bromide, timepidium bromide, prifinium bromide and diphemanil methylsulfate. In isolated smooth muscle organs (stomach, duodenum, ileum, colon, gall bladder and urinary bladder), anti-acetylcholine activities of HSR-902 were the most potent among these agents but its activity in urinary bladder, similar to findings in the cases of atropine and diphemanil methylsulfate, was relatively less potent than that of prifinium bromide, timepidium bromide and butylscopolamine bromide. Regarding the contractions of stomach, jejunum and ileum, which were induced by vagus nerve stimulation or acetylcholine, and on the ileum spontaneous motility, antispasmodic activities of HSR-902 were almost equal to or somewhat more potent than those of atropine, and its activities were more potent than those of prifinium bromide, timepidium bromide, diphemanil methylsulfate and butylscopolamine bromide. On the gall bladder pressure and the counts of perfusion through Oddi's Sphincter, these agents exhibited a similar inhibition and enhancement, respectively. In the case of urinary bladder contractions induced by pelvic nerve stimulation, these agents exhibited a weak inhibition. The inhibitory effect of HSR-902 was relatively less potent than that of other agents except atropine, which had little effect. HSR-902 was similar to atropine in this so-called “atropine-resistance”.

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