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KMID : 0376219640010020131
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Chonnam Medical Journal
1964 Volume.1 No. 2 p.131 ~ p.142
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Influence of interaventricular Phenoxybenzamine on Some actions of 5-Hydroxytryptamine
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Abstract
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It was attempted to investigate whether phenoxybenzamine (PBZ), a potent antagonist to 5-hydroxytryptamine(5-HT) in peripheral tissues, exerts entagonism to actions of 5-HT on the brain function. The results are as follows.
1) In mice PBZ could prevent the prolongation of hexobarbital sleeping time by 5-HT, but PBZ itself did not affect the hexobarbital effect. The prolongation of the hexobarbital sleeping time by Panax ginseng was not affected by PBZ.
2) The intraventricular administration of 5-HT in the rabbit produced sedation with low doses, but higher doses (5mg) produced miosis of short duration, tremor over the whole body, repiratory accelaration, but death ensued.
3) The intraventricular administration of PBZ (5mg) produced sedation, respiratory depression, abolition of the righting reflex, and ultimately death.
4) The tremor and ataxia, elicited by the intraventricular 5-HT, were abolished by administering PBZ into the lateral ventricle. When 5-HT was given intraventricularly following intraventricular PBZ administration the pupil constriction, tremor and respiratory acceleraton, which were usually observed by the 5-HT, did not appear, or transitory and weak, even when they appeared.
5) The blood pressure of the rabbit was not moditied by intraventricular 5-HT. It did not affect the blood pressure responses to intravenous 5-HT, epinephrine, angiotensin and isopropylarerenol, but the pressure rise due to bilateral carotid occlusion was diminished.
6) The intraventricular PBZ abolished or markedly inhibited the pressor response to intravenous epinephrine and the depressor one to intravenous 5-HT. The common carotid occlustion reflex was also wekened.
7) LSD-25, when adminisered intraventricularly, inhibited markedly the pressor response to intravenous epiniphrine and the depressor one to intravenous 5-HT, shilst BOL-148 and deseril, given by the same route, did not affect the action of the epinephrine or 5-HT. intraventricular JB-516, a monoamine oxidase inhibitor, potentiated the hypotensive effect of 5-HT but little effect on theepinephrine effect.
8) When the pressor effect of epiniphrine was almost abolished by intraventricular PBZ, the pressor action of epinephrine could beobserved after section of the spinal cord at the 1st and 2nd cervical level.
From the sleeping time experiment in the mouse and the gross behavior of the rabbit, it was supposed that the central effect of PBZ and 5-HT seems to show antagonism, though the nature of the antagonism was not clear. In the blood pressure response of the rabbit, no antagonism was found between two substances. The similarity of intraventricular PBZ to LSD-25 effect was observed. They eqully prevented the blood pressure response to 5-HT and epiniphrine.
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