Kiro Shimamoto

Cardiovascular effects of sympathomimetic amines injected into the cerebral ventricles of rabbits

Abstract Adrenaline (10–200 μg) and noradrenaline (50 μg) when injected into the lateral cerebral ventricle of pentobarbital-anesthetized rabbits produced a fall in systemic blood pressure, a decrease in spontaneous heart rate and a stimulation of spontaneous respiration. Isoproterenol (50–200 μg) caused a fall in blood pressure and an acceleration of heart rate, whereas phenylephrine (200 μg) caused a slight rise in blood pressure in association with a decrease in heart rate. The hypotension and bradycardia induced by adrenaline were not significantly affected by bilateral vagotomy. Pretreatment of rabbits with intravenous reserpine reversed the adrenaline-induced hypotension to a hypertension and abolished the bradycardia induced, but did not affect the respiratory stimulation. The cardiovascular responses to intraventricular adrenaline were abolished by transection of the spinal cord. In unanesthetized rabbits adrenaline produced presser and cardio-stimulatory effects followed by depressor and cardio-inhibitory effects. These findings would suggest a centrally mediated hypotensive action of adrenaline in anesthetized rabbits but a hypertensive action in unanesthetized rabbits. Furthermore, changes in the cardiac function might be associated with changes in local blood flow, as postulated by Kaneko et al . (1960).

The mechanism of antagonism between apomorphine and metoclopramide on unit discharges from nuclear structures in the brainstem of the cat

Abstract Effects of apomorphine and metoclopramide were studied on the spontaneous unit discharges in the single neurons of nuclear structures of brainstem in the ence´phale isole´preparations of cats. Apomorphine increased significantly the spontaneous discharge frequencies of single neurons in the Nucleus tractus solitarii, but did not influence the frequencies in the Nucleus vestibularis lateralis and Nucleus sensorius superior n. trigemini and the number of spikes per volley in the inspiratory unit discharges. Metoclopramide decreased significantly the firing rate of unit discharges in the Nucleus tractus solitarii and Nucleus vestibularis lateralis, while the unit discharges of the Nucleus sensorius superior n. trigemini and the rhythmic unit discharges corresponding to inspiration were not modified by metoclopramide. The acceleration of spontaneous discharge frequencies of the Nucleus tractus solitarii induced by apomorphine was completely blocked by the supplement of metoclopramide. Metoclopramide prevented retching and vomiting elicited by electrical stimulation of the Nucleus tractus solitarii. In some animals, metoclopramide produced a transient alert pattern in the cortical and hippocampal EEG and depressed slightly the recruiting response. However, it did not affect the reticular arousal response and the evoked click potentials in the auditory cortex.

Chemical and pharmacological studies on the in vitro cultivated ergot

In succession to the first report on the pharmacological studies on the in vitro cultivated ergot, the fluid extract of the mycelium and the filtrate of some ergot species (Claviceps purpurea separated by Prof. Katagiri, Claviceps purpurea separated from the rye-ergot, which were imported from North America and Claviceps separated from ergot of Agrogyrum semicostatum), which were cultivated in vitro on various synthetic culture media modifing the cultural pH, cultural period and cultural temperature, were studied systematically. The results obtained are as follows : 1) The oxytocic potency of the fluid extract of the mycelium of the third were 4 to 8 times stronger than that of the first and 2 to 4 times stronger than the second on the extirpated virgin guinea pigs uterus in vitro. Only the extract of mycelium of the latter showed the cock comb reaction and the adrenolytic action on the extirpated uterus and ileum of rabbit in vitro. As the amounts of histamine in these extracts, assayed by Dale-Schulzs method using the extirpated guinea pigs ileum, were considerably small, the oxytocic substances in the extracts resulted from the specific ergot alkaloids. 2) On the other hand, the fluid extracts of all the filtrates showed the cock comb reaction and adrenolytic action as well as the oxytocic action similar to that of the mycelium. 3) The alternation of the cultural conditions using various composition of natural and artificial cultural media and pH did not modified the pharmacological action essentially. However the oxytocic potency of the fluid extract of mycelium on artificial cultural media were somewhat stronger than that on natural cultural media. 4) Alternation of the cultural period for 1 to 4 weeks and the cultural temperature for 5 to 27°C also did not modified the pharmacological action of the fluid extract of mycelium and filtrate.