Some pharmacological effects of a potent tremorgenic mycotoxin, fumitremorgin A (FTA), on the rabbit were studied. FTA (10-200 μg/kg, i.v.) caused clonic and tonic convulsion accompanied by nystagmus and miosis in conscious rabbits, after a latent period. Even in decorticated or decerebrated rabbits, FTA (100-200 μg/kg, i.v.) could induce violent motor effects similar to those observed in conscious rabbits. Under light anesthesia with urethane and chloralose, a higher dosage (more than 100 μg/kg) was needed to cause clonic and tonic convulsion. FTA facilitated phrenic nerve discharges as well as efferent discharges of the vagal nerve and the cervical sympathetic nerve. Hypertention induced by FTA was inhibited by phentolamine, while bradycardia and arrhythmia caused by this toxin was abolished by atropine or bilateral vagotomy. The electroencephalogram showed persistent strong arousal response after intravenous injection of FTA. A seizure pattern was never observed. It was suggested that the main site of action of FTA was in the brain stem.
Descarboxyprothrombin (PIVKA II) is a precursor of prothrombin without biological activity, and it increases with vitamin K deficiency. We studied the time course changes in liver and plasma levels of PIVKA II during the progress of vitamin K deficiency in rats. Good correlation was observed between liver PIVKA II and plasma PIVKA II and between liver or plasma PIVKA II and plasma prothrombin in experiments in which rats were fed a vitamin K-deficient diet. Feeding of a vitamin K-deficient diet or fasting caused marked increases in liver and plasma PIVKA II in male rats and a weaker response in female rats. Warfarin, a vitamin K antagonist, caused an abrupt increase in liver PIVKA II, but the increase in plasma PIVKA II was delayed about 3 hr. Plasma prothrombin decreased from about 30 min later. Factor VII decreased similarly to prothrombin, and changes in the prothrombin time and activated partial thromboplastin time were slower than the changes in these substances. Sex differences were not seen in these warfarin actions. These observations indicate that liver and plasma PIVKA II are sensitive markers of vitamin K deficiency in rats, and assay of PIVKA II can be useful for analyzing the action mechanism of drugs which influence blood coagulation.
The effect of water temperature during restraint and water-immersion stress (RWIS) on gastric regional blood flow, acid secretion and ulcer formation were compared to those of restraint stress (RS) alone in rats. RS had no effect on the gastric regional blood flow. In contrast, the gastric regional blood flow was significantly decreased by RWIS. A water temperature dependent reduction of gastric regional blood flow induced by RWIS was observed between 20°C and 30°C. The decrease in gastric regional blood flow for RWIS rats was related to a lowering of the body temperature, which almost coincided with the temperature of water for the immersion. The gastric acid output was not influenced by RS. However, RWIS significantly increased the gastric acid output. The temperature of water in order of increasing acid output induced by RWIS was 25°C>30°C> 20°C. Little ulcer formation was found in RS rats, while exposure to RWIS caused marked ulceration. The temperature of water in order of severity of ulceration by RWIS was 25°C>20°C>30°C. The severity of ulceration was not related to the decrease in gastric regional blood flow or increase of acid output, but was correlated to the ratio of the gastric blood flow/the acid output. These findings suggest that the decrease of gastric regional blood flow is in good agreement with the fall of body temperature, and the combined effects of the gastric blood flow and the acid secretion are involved in the ulceration caused by RWIS.
Effects of restraint stress on humoral immune responses were investigated in mice. Mice were restrained for 12 hours per day at nighttime and released at daytime for 2 consecutive days, either before or after sheep red blood cell (SRBC) immunization. The antibody response to SRBC was markedly suppressed in mice that were restrained before antigen injection. In contrast, the response was not significantly affected when the stress was loaded after immunization. Oral administration of 10 mg/kg diazepam prevented the stress-induced suppression of anti-SRBC antibody response. On the other hand, antibody responses to T cell-independent antigens such as trinitrophenylated (TNP)-Ficoll and TNP-lipopolysaccharide were not suppressed. These results suggest that the restraint stress causes dysfunction of T cell populations in mice.
The influences of restraint stress on the functions of T cells, B cells and adherent cells in antibody responses were investigated. Antibody response against sheep red blood cells (SRBC), a T cell-dependent antigen, in cultured splenocytes from restrained mice was reduced to about 40-50% of that from the control mice. Addition of normal T cells to these cultures, however, restored the suppressed response. Moreover, helper T cell activities were lowered in restrained mice. On the other hand, suppressor T cell activities induced by both concanavalin A (Con A) and SRBC were significantly decreased in restrained mice. However, the antibody responses to T cell-independent antigens in stressed mice were approximately 40% higher than the control response. These enhancemant were also observed in T cell-depleted splenocytes. Polyclonal antibody response induced by lipopolysaccharide (LPS) was increased in stressed mice. Antigen presenting cell activities were little influenced by restraint stress. Proliferative response to Con A, but not that to LPS, was suppressed in splenocytes from restrained mice. These results suggest that both helper and suppressor activities of T cells are suppressed, but B cell activity is rather enhanced in splenocytes from restrained mice.
To clarify the histamine (HA) dynamics in peripheral tissues, effects of drugs on the tissue HA and tele-methylhistamine (t-MH) levels were studied in mice. α-Fluoromethylhistidine (50 mg/kg, i.p.) significantly decreased the HA level in the stomach, but not in the liver, heart, ileum, submandibular gland and skin of mice. This compound had no significant effect on the t-MH level in any tissue examined. In non-fasted and 24-hr fasted animals, the t-MH level in the liver, heart and ileum was significantly increased by treatment with aminoguanidine (10 mg/kg, i.p.) plus pargyline (65 mg/kg, i.p.). However, in mice fasted for 48 hr, this treatment was ineffective in increasing the t-MH level in the heart and ileum, suggesting that the t-MH level in some peripheral tissues is under the influence of the food intake. Even if HA is synthetized and then metabolized in the peripheral tissues, the size of the HA pool with a rapid turnover in each tissue except for the gastric tissue seems to be very small.
We examined the hypersecretory function of the isolated, blood-perfused pancreas of dogs with experimentaly obstructive jaundice. There was no difference in basal pancreatic secretion between control dogs and obstructively jaundiced dogs. Secretin- or pancreozymin-stimulated increase in total values for pancreatic juice flow, bicarbonate, protein and amylase were greater in dogs with obstructive jaundice than in control dogs; however, concentrations of bicarbonate, protein and amylase were unchanged in each group. Acetylcholine-stimulated increase in total values and concentrations of these factors were the same in dogs with obstructive jaundice and controls. These data suggest that hypersensitivity of the pancreas to secretin and pancreozymin may be one of the main mechanisms of pancreatic hypersecretion.
The oral administration of diethyldithiocarbamate (DTC) prevented hepatic necrosis induced by N-methylformamide (NMF) in ddY-strain mice, in more susceptible BALB/c mice and in diethylmaleate-treated mice in which NMF-hepatotoxicity was potentiated, as evidenced by suppression of increases of plasma glutamic pyruvic transaminase activity and liver calcium content or by histological observations. Early depletion of liver glutathione following NMF administration was also prevented by DTC. DTC markedly delayed the in vivo metabolism of NMF as indicated by a prolonged retention of plasma and liver NMF levels and an enhancement of urinary excretion of NMF. These observations support a bio-activation mechanism for NMF hepatotoxicity, and the hepatoprotective action of DTC may be due to an inhibition of the metabolic activation of NMF. Hepatotoxic manifestations after repeated administration of NMF also tended to be ameliorated by simultaneous treatment with DTC. Cotreatment with DTC, however, decreased the antitumor activity of NMF against Ehrlich ascites tumors, and Sarcoma 180. This also implies the involvement of a bioactivation mechanism in the antitumor action of NMF, but further studies are necessary to confirm this point. The possible therapeutic value of DTC as a hepatoprotector may be diminished by the suppression of the antitumor activity of NMF.
The mechanisms of the marked inhibitory effects of 10 ppm formaldehyde (HCHO) inhalation on heart rate and respiratory movement were investigated in unanesthetized rabbits. Inhibition of the heart rate and respiratory movement induced by HCHO inhalation was caused by a reflex reaction during sensory irritation of the upper respiratory tract, mainly the nasal mucosa, but not of the lower respiratory tract, mainly the lung. These reflex reactions, particularly decreases in the heart rate, were not blocked by vagotomy, atropine or prazosin, but were blocked by propranolol, phenoxybenzamine, phentolamine, yohimbine and guanethidine. These results suggest that these reflex reactions are derived from sympathetic nervous activity rather than parasympathetic nervous activity, and the reflex bradycardia is caused by inhibiting the transmitter release at the adrenergic nerve endings.
The effects of 8-(2-dimethylaminoethyl)-3-oxo-4-phenyl-1-thia-4, 8-diazaspiro [4, 5] decane dihydrochloride monohydrate (Y-8845) on carbon tetrachloride (CCl4)-induced liver injury were investigated in rats. CCl4-induced attenuation of the plasma cyclic AMP (cAMP) response to glucagon stimulation was significantly prevented by pretreatment with Y-8845. Y-8845 also effectively suppressed the increases in the activities of serum transaminases as well as the decreases in microsomal glucose-6-phosphatase activity and microsomal cytochrome P-450 concentrations induced by CCl4. In rats at 72 hr after CCl4 administration, the plasma cAMP response to glucagon, microsomal glucose-6-phosphatase activity and P-450 concentration were all below the control level. Y-8845 treatment after CCl4 administration rectified these reductions to nearly normal levels. Furthermore, Y-8845 stimulated DNA synthesis during liver regeneration after CCl4 intoxication. These results demonstrate that Y-8845 has a protective effect against CCl4-induced injury in the liver and a stimulating effect on the recovery of the damaged liver.
This report deals with the effect of cholecystokinin octapeptide (CCK-8) on the regulation of the behavior stimulated by dopaminergic drugs. Bilateral injection of CCK-8 (1 μg per side) into the nucleus caudatus significantly reduced the locomotor hyperactivity induced by methamphetamine. Stereotyped sniffing and yawning occurred after intrastriatal administration of apomorphine (20 μg per side). Injections of CCK-8 into the nucleus caudatus completely inhibited the sniffing, but did not affect the yawning induced by apomorphine. It also had no effect on the basal dopamine (DA) level or the methamphetamine-induced DA level in the striatum. These results suggest that the injection of CCK-8 into the nucleus caudatus selectively inhibited the function of the dopaminergic system in the striatum, and blocked post-synaptic DA receptors.
A peptide with strong activity to contract isolated whole chick rectum, RC-substance, in an acid-acetone extract prepared from 2.0 kg wet weight of chicken rectums was isolated by gel filtration on Sephadex G-25, ion exchange chromatography on a SP-Sephadex C-25 column, and high voltage paper chromatography. The close purity of this substance was established by high performance liquid chromatography (HPLC). The RC-substance displayed the same pharmacological and enzymatic properties as bovine neurotensin (NT). However, it differed from bovine NT in its behavior during the ion exchange chromatography, in its mobility during the electrophoresis, and in its retention time on HPLC. The amino acid analysis by a conventional OPA method revealed that all ten amino acid residues of which molar ratios were integral were common with those of chicken NT. Its biological activities were equipotent to those of bovine NT, suggesting the presence of proline in the COOH-terminal hexapeptide. From these results, it can be concluded that the RC-substance is identical to chicken NT. Exposure to high concentrations of bovine NT rendered the rectal smooth muscle of the chicken insensitive to subsequent applications of the RC-substance as well as bovine NT. This desensitization also reduced specifically the contractile resonpses of the rectal muscle elicited by non-adrenergic and non-cholinergic (NANC) nerve stimulation, suggesting a possible physiological role of the RC-substance as the neurotransmitter of NANC neurones.
Neuronal cell suspensions were implanted into the striatum of female rats that showed apomorphine-induced rotation and a reduction in striatal dopamine after intranigral treatment with 6-hydroxydopamine. The apomorphine-induced rotation was significantly suppressed by the transplantation in 12 out of 64 rats. DOPA accumulation and dopamine level (6.3 and 3.4%, respectively, compared with those of uncompensated rats) in the striatum following treatment with an amino acid decarboxylase inhibitor were slightly restored in compensated rats.