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Biomedical subjects

G D Leach

Publications and source records attributed to G D Leach.

At least 37 records · Page 2Linked to original sources
PubMed1970

The effect of some foreign anions on suxamethonium blockade of the isolated rat diaphragm preparation.

1. The pharmacology of suxamethonium blockade of the rat phrenic nerve-diaphragm preparation has been studied in the presence of some foreign anions.2. Blockade proceeded in two distinct phases in both normal and modified Krebs solution.3. In normal Krebs solution the characteristics bore no close resemblance to either depolarizing or competitive type blockade.4. In the presence of foreign anions the characteristics of the blockade more closely resembled those of depolarization.5. There was an increase in the sensitivity of the motor end-plate region of the muscle to the depolarizing action of acetylcholine, carbachol and suxamethonium in the presence of the anions.6. Although the anions enhanced the depolarizing activity of suxamethonium, the blocking potency of the drug was unaltered.7. It is suggested that end-plate depolarization plays little part in suxamethonium blockade of the isolated rat diaphragm and that desensitization is the primary cause of the blockade.

Acetylcholine↗
PubMed1970

The contribution of the sympathetic nervous system to the development and maintenance of experimental hypertension in the rat.

1. Experimental hypertension in the rat, induced either by renal artery stenosis or by treatment with deoxycorticosterone acetate (DCA) developed maximally over a period of 8 weeks. In both types of hypertension the rate of development was unaffected by immunosympathectomy or by chemical sympathectomy following the administration of 6-hydroxydopamine.2. The effect of 6-hydroxydopamine on chronic renal hypertensive rats was to produce a hypotensive action of longer duration than when similarly administered to DCA-induced hypertensive or normotensive rats. Reserpine (5-10 mg/kg intraperitoneally) produced a more marked hypotensive effect on both types of hypertensive rats although it was of much shorter duration.3. It is concluded that experimental hypertension of renal origin or induced by DCA treatment can develop even though most of the sympathetic nervous system has been destroyed. The maintenance of chronic hypertension in these conditions may depend on the adrenal glands or a hormonal system as yet undetected.

Animals↗
PubMed1969

The role of the sympathetic nervous system in the cardiovascular responses to angiotensin in the pithed rat.

1. Angiotensin (200-500 ng, intravenously) produced a biphasic pressor response accompanied by reflex bradycardia in rats anaesthetized with sodium pentobarbitone. In pithed rats and in anaesthetized animals treated with a ganglion blocking agent there was a similar pressor response but an increase in the heart rate which was coincident with the second phase of the pressor response. In pithed preparations an increase in cardiac contractile force accompanied the heart rate changes.2. Acute or chronic adrenalectomy did not alter the pressor responses and chronotropic effect of angiotensin in the pithed rat. Propranolol abolished the chronotropic and inotropic action of angiotensin, but left the biphasic pressor response unaltered. Bethanidine, or pretreatment with reserpine, altered the pressor response to a simple rise, and also abolished the chronotropic action of angiotensin. Phentolamine also abolished the second pressor component. Desmethylimipramine produced a marked potentiation of the cardiovascular effects of angiotensin at all dose levels tested (10-500 ng).3. It is concluded that in the rat only large doses of angiotensin are capable of indirectly stimulating the sympathetic nerves either at the site of their ganglionic cells or their post-ganglionic nerve ending.

Adrenalectomy↗