Pharmacological and electrophysiological studies using cerebellar slice preparations were reviewed and discussed primarily from a neuropharmacological point of view. Particular reference was made to the potential usefulness of cerebellar slices for studies of neurotransmitters, pre- and postsynaptic receptors, ionic mechanisms and the mechanism of action of CNS drugs. Technical instructions for the use of cerebellar slices were also presented in hopes of facilitating pharmacological research in vitro.

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The mechanism for the enhancing effect of pyrogen (lipopolysaccharide, LPS) on the fetal toxicity of acetylsalicylic acid (ASA) was studied in pregnant rats. The lethality of ASA was significantly enhanced by LPS in male rats. The fetal toxicity of ASA including fetal death, resorption, growth retardation, and skeletal anomalies (wavy rib and asymmetry of sternebra) was slightly observed in the dams that received a single dose of ASA (125 to 500 mg/kg, p.o.) on the 15th day of gestation, but it was markedly increased by LPS (20 μg/kg, i.v.). The enhancement of the toxicity of ASA by LPS was also observed in the maternal body weight gain until term. The plasma concentrations of ASA and salicylic acid (SA), the major metabolite of ASA, were increased by LPS. The tissue concentrations of SA were also increased in the following order: placenta, brain, fetus, uterus, liver and kidney. The ATP levels of placenta and fetus were not influenced by ASA alone, but markedly decreased by both LPS and ASA.

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We performed studies on the mechanisms for the teratogenicity of trypan blue (TB) that is known as a potent teratogenic dye in rodents. TB was administered to Wistar rats at various doses and at different stages of gestation. Teratogenicity and embryolethality were observed by a single (50 and 250 mg/kg) subcutaneous injection and three (25 and 50 mg/kg) subcutaneous injections of TB daily from day 7 of pregnancy. The incidences of malformations in groups given 50 and 250 mg/kg on day 7 were 12 and 59%, respectively. Most of the fetuses with external malformations were accompanied with skeletal and/or internal anomalies. The types of frequently occurring malformations were as follows: exencephaly, spina bifida, tail anomaly, vertebral deformity, hydrocephaly and heart anomaly. Fetal toxicity was decreased after treatment with the mixture of TB and normal rat serum. The serum level of TB in pregnant rats increased to 308 μg/ml at one hour after subcutaneous treatment with TB 50 mg/kg and decreased rapidly, but remained at 58 μg/ml 72 hours later. Lower serum levels of TB were observed in pregnant rats given TB with serum. No fetotoxic effects of serum from pregnant rats treated with TB were observed in recipient rats given the serum on day 7, 8 and 9 of pregnancy.

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Effects of flunarizine (0.3-3 mg/kg, i.v.) on cerebral circulation were compared with those of cinnarizine (0.3-3 mg/kg, i.v.) and papaverine (0.1-1 mg/kg, i.v.) in anaesthetized dogs and cats. In dogs any of the three drugs caused a dose-related increase in vertebral, common carotid, and femoral arterial blood flow, while a transient decrease in renal blood flow was seen. In particular, the vasodilatation caused by flunarizine and cinnarizine was much more marked in the vertebral vascular beds as compared to the other ones. Flunarizine (10 and 30 mg/kg, intraduodenally) caused a greater and more prolonged increase in the vertebral blood flow than cinnarizine and papaverine did when they were used in the same doses. Concerning the local circulation in cats, flunarizine and cinnarizine produced a marked flow increase in the cerebellar cortex, and apparent blood flow and pO₂ increases in the cerebral cortex with no observable concomitant changes in arterial blood pO₂ and pCO₂; but a slight decrease in hippocampal blood flow without any consistent effect in hypothalamic blood flow. In this study, flunarizine was shown to have a more prolonged pharmacological activity on the responses of the cerebral circulation than equal doses of cinnarizine or papaverine.

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Some pharmacological actions of intraperitoneally (i.p.) administered d-pseudoephedrine (d-pseudo) on the central nervous system of mice were compared with those of l-ephedrine (l-eph). Locomotor activity was increased by l-eph (50, 100 and 200 mg/kg, ) but not by d-pseudo (50, 100 and 200 mg/kg). Wheel-revolving activity was reduced by a 200 mg/kg dose of both drugs. Rectal temperature was increased by l-eph at 50, 100 and 200 mg/kg. However, it was decreased by 50 and 100 mg/kg doses of d-pseudo, and the change in response to 200 mg/kg of d-pseudo was biphasic, decreasing first and increasing subsequently. Pentobarbital-induced sleeping time was shortened by l-eph (50 and 100 mg/kg), but was not influenced by any of the doses of d-pseudo. In the experiment on locomotor activity, L-3, 4-dihydroxyphenylalanine (400 mg/kg, i.p.) potentiated the effects of d-pseudo and l-eph, but reserpine (1 mg/kg, day × 5 days, i.p.) and 6-hydroxydopamine (40 μg/mouse, intracerebroventricular injection) potentiated only the effect of l-eph. These results suggest that the effect of d-pseudo on the central nervous system of mouse is not only weaker than that of l-eph, but also the mechanisms of action of these two substances are different.

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β₂-Microglobulin (β₂-M) was purified from the urine of rats treated with cephaloridine by a combination of ammonium sulfate precipitation, gel chromatography, ion exchange chromatography, zone electrophoresis, and isoelectric focusing. The protein thus obtained was identified as β₂-M by its molecular weight, electrophoretic mobility, and amino acid composition and was confirmed as a single protein through polyacrylamide gel electrophoresis, Ouchterlony immunodiffusion analyses, and immunoelectrophoresis using rabbit anti-rat β₂-M sera. A radioimmunoassay was developed for the measurement of serum and urine β₂-M levels. In rats given gentamicin (20 or 80 mg/kg/day, s.c.) for 10 days, serum β₂-M was increased simultaneously with changes in common renal function parameters such as serum urea nitrogen, creatinine, and urinary protein. Urinary β₂-M was elevated from the early stage of nephropathy and correlated with renal morphological change, indicating that urinary β₂-M can be used as a sensitive and valuable index of renal tubular damage.

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Antihypertensive and related hemodynamic effects of trichlormethiazide (TCM), a thiazide, in DOC/saline hypertensive rats were investigated. To prepare hypertensive rats, 7-week-old male Wistar rats were subjected to nephrectomy of the left kidney, subcutaneously administered DOC (5 mg/kg × 3 times/week, or a 25-mg tablet), and given 1% saline solution as drinking water. When the systolic blood pressure of the rats reached about 200 mmHg, once-a-day oral administration of an arabic gum suspension of TCM was started. The results were: 1) Oral administration of TCM at no less than 3 mg/kg/day showed a dose-dependent, lasting antihypertensive effect throughout the experimental periods. 2) TCM administration effectively prevented the appearance of malignant hypertensive symptoms such as body weight loss, ischemia of the ocular fundus, and slight paralysis of extremities with the following pathological changes: hyalinization and fibrinoid necrosis of renal arteries and glomeruli, degeneration of renal tubules, and cardiac hypertrophy. 3) Although TCM had no effect throughout the experimental periods on the cardiac output (CO), which was determined by a modified dye-dilution method, total peripheral resistance (TPR) decreased from the first week of TCM administration. The antihypertensive effect of TCM in DOC/saline hypertensive rats is presumed to be associated with the decrease of TPR from early stages of therapy.

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Intravenous injections of guanfacine (1 μg-3 mg/kg) elevated dose-dependently blood pressure in adrenalectomized, pithed rats. The vasopressor activity of guanfacine was weaker than those of clonidine, an α₂-agonist and 1-phenylephrine, an α₁-agonist. However, the maximal response produced by guanfacine was the same as that produced by clonidine, while it was much smaller than that produced by 1-phenylephrine. The doseresponse curve to guanfacine for increase in blood pressure was shifted in a parallel fashion to the right by I mg/kg of yohimbine, an α₂-antagonist and by 1 mg/kg of phentolamine, a nonselective α₁- and α₂-antagonist. However, 0.1 mg/kg of prazosin, a selective α₁-antagonist, produced an inhibition of the blood pressure rise induced by higher doses of guanfacine, but not that induced by lower doses. Guanfacine (1 μg-1 mg/kg) inhibited dose-dependently the tachycardia induced by electrical stimulation of spinal nerves at C₇-Th₁ in adrenalectomized, pithed rats. The maximal inhibition by guanfacine of heart rate increase induced by electrical stimulation was about 60%. These inhibitory effects were antagonized by yohimbine and phentolamine, but not by prazosin. These results indicate that guanfacine is an α₂-agonist with approximately equal potency towards the pre- and postsynaptic α₂-adrenoceptors, just as clonidine is, but is weaker as an α₂-agonist than clonidine.

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The effects of SGB-483, a newly-synthesized hypotensive agent, on the blood pressure were studied in unanesthetized and anesthetized rats. SGB-483 produced a significant hypotensive action in the conscious SHR and renal hypertensive (clipping) rats, and it caused reversal of the pressor response to adrenaline in the anesthetized Wistar-Imamichi rats, SHR, and clipping rats. In an isolated guinea pig aorta preparation, SGB-483 competitively inhibited the contractile response to phenylephrine with a pA₂ value of 7.64±0.08. In pithed rats that were pretreated with β-adrenoceptor blocker, the pressor effect of adrenaline (1 μg/kg) was not completely blocked by either prazosin (1 mg/kg), an al-selective blocker, or yohimbine (1 mg/kg), an α₂-selective blocker. SGB-483 (1 mg/kg) had no effects on the prazosin-resistant part of the pressor effect of adrenaline, but significantly inhibited the yohimbine-resistant part. Clonidine-induced reversal of the tachycardia induced in the pithed rat by cardiac sympathetic nerve stimulation was unaffected by SGB-483, indicating that SGB-483 is a selective antagonist of the α₁-adrenoceptor.

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Alpha-methyldopa (α-MDP) is a widely used hypotensive agent, and it is considered to act on the central nervous system. In the present study, 6-hydroxydopa (6-OHDP) was injected into spontaneously hypertensive rats in a dose of 50 mg/kg on the 19th and 21st days of gestation. Dopamine contents were not changed, but norepinephrine (NE) decreased at 12 weeks of age. When the effect of α-MDP was examined at the age of 30 to 40 weeks, the decrease in blood pressure induced by 300 mg/kg α-MDP i.p. was significantly attenuated in the 6-OHDP treated rats. Whenever the hypotensive effects of α-MDP were inhibited, production of α-methylnorepinephrine (α-MNE) was markedly reduced only in the spinal cord. 6-Hydroxydopamine (6-OHDA) was also injected into the spinal cord at the C₄ level. Although α-MDP lowered blood pressure in both 6-OHDA treated and non-treated control rats, the decreased in 6-OHDA treated rats tended to be less pronounced. The accumulation of α-MNE in the caudal area of the spinal cord was markedly reduced. Furthermore, in order to destroy the spinal serotonergic neurons selectively, we used intraspinal 5, 7-dihydroxytryptamine (5, 7-DHT) in the same manner as 6-OHDA injection. In 5, 7-DHT treated rats, the blood pressure was decreased fully. These observations seem sufficient to hypothesize, although not to conclude, that the effect of α-MDP on the blood pressure is dependent at least partly on the biotransformation to α-MNE in the spinal noradrenergic neurons.

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