SUBSTANCE P IN BRAIN EXTRACTS

A SENSITIVE METHOD FOR THE ASSAY OF ANGIOTENSIN

A method is described for the assay of angiotensin on the rat colon. Under the conditions of the assay, the preparation is sensitive to angiotensin and relatively insensitive to 5-hydroxytryptamine, to histamine and to other substances which might be present in blood. Bradykinin and catechol amines do not interfere with the assay. Evidence is given for the specificity of the angiotensin receptors.

Thirty years of synaptosome research

Detached synapses (synaptosomes), first isolated by the author in 1958 and identified as such in 1960, are sealed presynaptic nerve terminals often with a portion of the target cell--sometimes amounting to a complete dendritic spine--adhering to their external surface. They can be prepared in high yield from brain tissue and also in decreasing yield from spinal cord, retina, sympathetic ganglia, myenteric plexus and electric organs. They are sealed structures which, under metabolizing conditions, respire, take up oxygen and glucose, extrude Na+, accumulate K+, maintain a normal membrane potential and, on depolarization, release transmitter in a Ca(2+)-dependent manner. They thus provide an excellent preparation with which to investigate synaptic function without the complications encountered with synapses in situ. They also serve as the parent fraction for preparations of synaptic vesicles and other synaptic components.

Cardiovascular effects of synthetic substance P in several species

In dogs anaesthetised with chloralose, infusion of synthetic substance P into the femoral artery caused marked elevation of femoral arterial blood flow which was well sustained during the infusion period. Doses less than 59 fmol/kg/min increased femoral arterial flow only, but larger doses caused transient hypotension accompanied by tachycardia. The administration of substance P by i.v. and intravertebral (i.vert.) arterial routes caused hypotension and tachycardia of similar pattern and magnitude to those produced by intrafemoral (i.f.) arterial infusion of equivalent doses. I.v. injection of substance P into rats and rabbits caused qualitatively similar cardiovascular effects to those in dogs, but higher doses were required for threshold responses. Substance P had little effect on the spontaneously beating isolated guinea-pig heart. Like many other vasodilator substances in vivo, substance P caused constriction of the isolated perfused ear vein from the rabbit. The results suggest that the major cardiovascular effect of synthetic substance P is vasodilatation and that a direct action on vascular smooth muscle is involved.

Evidence for substance P in the striato-nigral tract

The highest concentration of substnace P yet found in the mammalian brain is in the reticular part of the substantia nigra. The effect of various lesions on the substance P content of that region has been examined in the rat in order to determine the possible sources and paths of nigropetal substance P-containing fibers. Unilateral knife cuts which transect the medial forebrain bundle and medial portion of the crus cerebri at a premammillary level lead to a 90% reduction in substance P in the ipsilateral reticular part of substantia nigra, with no significant effect on contralateral values. Incomplete electrolytic lesions of the globus pallidus lead to a 50% decrease. These data indicate that descending uncrossed pathways provide most of the substance P in the reticular part of the substantia nigra, with the striato-nigral tract providing an important component.

The pharmacology of a new oxytocic principle from ox hypothalamus

1. An oxytocic substance has been isolated from ox hypothalamus by successive gel filtration on Sephadex G-25 and Sephadex G-50, and its pharmacology has been examined on three smooth muscle preparations.2. The substance has the same order of potency on rat uterus, guinea-pig ileum, and hen rectal caecum.3. The action of the substance on rat uterus was not abolished by thioglycollate.4. Atropine (1.0 mug/ml.), phenoxybenzamine (0.1 mug/ml.) and mepyramine (1.0 mug/ml.) did not block the smooth muscle action of the substance.5. Drug action, relative potency, and log dose-response relationships distinguish the substance from 5-hydroxytryptamine, acetylcholine, oxytocin, vasopressin, angiotensin amide, bradykinin, and purified preparations of substance P.

Action of substance P on the central nervous system of a goat

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The movement of noradrenaline in sympathetic nerves

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