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Male Wistar rats weighing 75 to 85 g and maintained on a thiamine deficient diet for 33 days showed growth inhibition with the principal manifestation of significant weight loss from about the 28 day of experimental feeding. Symptoms of polyneuritis were also evident. On the 20th day of feeding and thereafter, rats on the thiamine deficient diet had a persistent erection. This was observed in 7% of the rats on a thiamine deficient group on day 20, 30.7% on day 25, 63.6% on day 30, and 100% on day 33. Effects of thiamine hydrochloride, in a single dose of 1 mg/kg given subcutaneously on the symptoms of thiamine deficiency were investigated. The treated rats recovered from the polyneuritic symptoms, and persistent erection disappeared in one out of 5 rats on the 3rd day and in 2 more rats on the 7th day. Persistent erection disappeared completely in rats maintained on a thiamine sufficient diet 3 days after single subcutaneous administration of thiamine HCl. These observations suggest that persistent erection was brought on as a consequence of thiamine deficiency.

Effect of various combinations of Platycodi Radix water soluble extracts (Pla), 1-ephedrine (1-eph), d-pseudoephedrine (d-pseudo) and Ipecacuanhae Radix water soluble extracts (Ipe) on acute toxicity were examined in mice. Oral LD50 of Ipe, d-pseudo and 1-eph was 490 (415--578) mg/kg, 1550 (1360--1767) mg/kg and 1400 (1102--1778) mg/kg, respectively, while that of Pla was over 10 g. LD50 of Pla Ipe, d-pseudo and 1-eph given intraperitoneally was 1400 (1228--1596) mg/kg 235 (210--263) mg/kg, 245 (229--262) mg/kg and 300 (259--348) mg/kg, respectively. The ratio of the predicted LD50 value, which was calculated on the assumption that each component drug would be additively toxic when combined, to the observed LD50 value was used for comparison. The combination of d-pseudo with Pla gave a significantly greater LD50 value than the predicted LD50 value, while the combination of 1-eph with Pla showed a LD50 value which was not significantly different from Finney's additive model. A combination of d-pseudo with 1-eph and Ipe, and of 1-eph with Ipe showed a LD50 value which was not significantly different from that of the additive model.

The effect of 1-dihydroxyphenylalnine (l-dopa) on phenol-induced tremor was studied in detail in mice. The tremor was observed in every mouse a few minutes after subcutaneous injection of phenol. The tremor induced by phenol with a concentration of 1% was observed as slight, and continued for 35 minutes. In mice pretreated with 1-dopa the phenol-induced tremor was strengthened in a dose-dependent manner. The combined effect of Ro4-4602, which is the peripheral decaboxylase inhibitor, and 50mg/kg l-dopa was equal to the effect of 200mg/kg l-dopa alone. Intracerebroventricular injection of dopamine also strengthened the tremor induced by phenol. But a-methyl-p-tyrosine, which is the inhibitor of dopamine synthesis, was not effective within the dose range of 50-200mg/kg. Our findings suggest that stimulation of dopaminergic system in the central nervous system can increase the phenol-induced tremor.

Male Wistar rats maintained on a thiamine deficient diet showed muricide aggression. On the 30th day of experimental feeding, the incidence was 70% and the killing latency was very short in the thiamine deficient killer-rats. They did not kill their rat-pups. Intraventricular injection of serotonin (5-HT) was effective in suppressing the muricide induced by thiamine deficiency. The suppressive effect of 5-HT was strongly antagonized by antiserotonergic agents, morphine and chlorpromazine. Moreover, the suppressive effect of 5-HT was potentiated by iproniazid, a monoamine oxidase inhibitor. Various antidepressants had suppressive effects on this muricide to varying degrees. Muricide induced by thiamine deficiency was more potently suppressed by the tricyclic antidepressants which inhibit 5-HT uptake rather than noradrenaline uptake. Our results in these experiments strengthened the hypothesis that central serotonergic neurons are involved in the inhibition of the muricide aggression in thiamine deficient killer-rats.

The emotional behavioral aspects and the interaction between the changes of the polyamine contents and muricide response in thiamine deficient rats were investigated. In the thiamine deficient group, there was evidence of muricide and such increased progressively with advanced thiamine deficient feeding. This muricide was characteristic in the following respects; 1) the killer-rats did not eat but only kill a mouse and it was quite difficult to remove a sacrificed animal from the cage. 2) they bit at random into any body region of the mouse. 3) the killer-rats did not bite inanimate objects such as nails nor chalk. 4) the muricide induced by thiamine deficiency could not be suppressed by a single injection of thiamine HCl. On the 30th day of the experimental feeding, both spermidine and spermine levels in the brain of the thiamine deficient group decreased significantly as compared to the control and the pair-fed groups. Both spermidine and spermine levels were reversed to the control levels with a intraperitoneal administration of thiamine. There were no significant differences in spermine and spermidine levels between the killer-rats and non-killer-rats in the thiamine deficient group.

It is well known that rats maintained on a thiamine deficient diet exhibit significant weight loss, decrease in heart frequency, behavioral disorders such as circling movements, muricide aggression as well as symptoms of polyneuritis. After a series of pharmacological studies on thiamine deficient rats, I reported that the actions of certain drugs affecting the central nervous system were modified by acute thiamine deficiency in animals. In brief, thiamine deficiency increased sensitivity to the hypnotic action of barbiturates and reduced the cataleptic action by tetrabenazine4). I am planning to investigate the effect of analgesics (morphine, pentazocine, aspirin……) on thiamine deficient animals, since little is known about changes in the pain threshold following severe thiamine deficiency. In this study, an attempt was made to investigate the changes in the pain threshold of rats as a consequence of thiamine deficiency.

Chlorpheniramine (5–10 mg/kg) showed a dose- dependent suppressive effect on muricide induced by thiamine deficiency at 1 hr after oral administration. The ED50 value for muricidal suppression was about 7.1 mg/kg (95% confidence limits, 5.4–9.3 mg/kg). The maximum effect of muricidal suppression lasted for 1–2 hr after oral dosage (10 mg/kg). Chlorpheniramine was detectable at 10 min in the blood and brain of thiamine deficient killer-rats by using a high-performance liquid chromatographic method. Maximum brain and blood levels of chlorpheniramine appeared at 45 and 60 min, respectively. In terms of regional distribution, the highest levels were measured in the limbic system, especially in the hippocampus. Although neither blood nor brain levels of chlorpheniramine reflect its pharmacological activity, it can easily enter the brain and suppress muricide more potently than imipramine.

The effects of thiamine deficiency on pharmacological and pharmacokinetic activities of chlorpheniramine were investigated in rats. Chlorpheniramine (5–10 mg/kg) showed a dose-dependent suppressive effect on muricide induced by thiamine deficiency. The ED 50 value for muricidal suppression at 1 hr was approximately 7.1 mg/kg (95% confidence limits, 5.4–9.3 mg/kg) after oral administration. Using a high-performance liquid chromatographic (HPLC) method, chlorpheniramine was detectable at 10 min in the blood and brain of rats. The present pharmacokinetic data suggest that chlorpheniramine can easily pass through the blood-brain barrier (B.B.B.) and enter the brain. It is stored therein and is later slowly released and excreted. In thiamine deficient rats, chlorpheniramine entered the brain in much higher concentrations than in normal and pair-fed rats, and significantly higher levels were maintained for a period of 1.5 hr. These results suggest that thiamine deficiency affects pharmacological and pharmacokinetic activities in rats, and support the view that there is a malfunction of the B.B.B. in thiamine deficient rats. These factors should be taken into consideration in clinical usage and dosage.

Effects of polyamines on the central nervous system were studied in mice. Intraperitoneal administration of Spermidine (SPD) and Spermine (SPM) decreased spontaneous motor activity as measured by either the photo-cell counters method or the open-field test and lowered rectal temperature. A significant prolongation of sleeping time after pentobarbital was confirmed in small doses of SPD and SPM which had slight influence on spontaneous motor activity. The time to convulsion and death induced by strychnine was elongated by SPD and SPM. SPM in small doses inhibited writhing responses induced by 0.7% acetic acid. In addition, methamphetamine-induced hyperactivity and conditioned avoidance response were blocked by SPM in doses which decreased spontaneous motor activity. In all experiments, SPM appeared to have a powerful pharmacological activity compared with SPD. LD50 for SPD and SPM was 620 (500-769) mg/kg i.p. and 310 (200-480) mg/kg i.p., respectively.

The effects of histidine treatment on histamine levels in brain regions and the muricidal suppression in thiamine deficient rats were examined. Intraperitoneal administration of L-histidine significantly increased the histamine levels in several regions of normal and thiamine deficient rats. A dose of 200 mg/kg of histidine suppressed muricide induced by thiamine deficiency. The histamine levels of those thiamine-deficient killer-rats, whose muricide was suppressed by histidine treatment, were significantly higher in the amygdala, striatum and hypothalamus than of those whose muricide was not suppressed. It is suggested that the activation of central histaminergic neuron systems, especially in the amygdala, may underlie the mechanism of muricidal suppression by histidine treatment in thiamine deficient rats.

Analgesia, catalepsy, head twitch response and hypothermia were observed after intracerebroventricular (i.e.v.) histamine in mice. These symptoms are also seen when morphine and opioid peptides are injected into animals. Histamine has been known to have a role in the tolerance and physical dependence to morphine. In the current study, we examined the opiate-like effects by i.e.v. histamine, especially using catalepsy as an index. The results are as follows: i.e.v. histamine causes cataleptic state in a dose dependent manner (5-1000μg). H1-histamine receptor blocking agents such as pyrilamine, diphenhydramine and cyproheptadine reduced the cataleptic scores in a dose-dependent manner (5-20mg/kg, i.p.). However, H2-histamine receptor blocking agents such as Cimetidine and metiamide have no influence on it (10-100μg, i.e.v.). These results showed the action of histamine is mediated through H1-receptor in the case of catalepsy. Some antidepressants without iprindole reduced the catalepsy and showed their utility as H1-histamine receptor blocking agents. We also investigated certain mechanism of catalepsy in connection with other neurotransmitters. In the central cholinergic system, muscarinic steps are involved in its action since atropine and sparteine reduced the catalepsy, but mecamylamine is without effect. Naloxone reduced the catalepsy (5-10mg/kg). These results showed actions of histamine may stimulate the cholinergic and opioid systems.