EFFECT OF TUBOCURARINE ON RESPIRATORY AND NONRESPIRATORY MUSCLE POWER IN MAN

On human volunteers the degree of muscular depression in respiratory power and handgrip strength was determined when ability to raise the head was almost or completely abolished by (+) tubocurarine. In one series the course of restitution after maximal depression of head lift, handgrip, maximal inspiratory and expiratory flows were compared. In the second series measurements of maximal inspiratory and expiratory pressures replaced those of maximal flows. In all experiments the respiratory functions were consistently much less affected than head lift and handgrip. Of the two last mentioned the power in head lift was always most affected. The results suggest that, in normal man, respiratory muscle power is relatively well preserved when curarization is carried to the point where the ability to raise the head is nearly abolished and the strength in handgrip is severely retarded.

effect on head lift

Submitted on November 15, 1963

THE EFFECTS OF GANGLION-BLOCKING AND POSTGANGLIONIC SYMPATHOLYTIC DRUGS ON PREPARATIONS OF THE GUINEA-PIG VAS DEFERENS

The contractions of the guinea-pig isolated vas deferens elicited by electrical stimulation of the hypogastric nerve were completely blocked by the following drugs: guanethidine, bretylium, dimethylphenylpiperazinium hydrochloride, nicotine, pempidine, hexamethonium, hemicholinium, D-tubocurarine and procaine. However, when the vas deferens was stimulated through an electrode in its lumen, the contractions in response to frequent, short stimuli (50 shocks/sec, 1 msec duration) were blocked by guanethidine, bretylium and dimethylphenylpiperazinium, but were not affected by the remaining drugs, except that procaine and hemicholinium each caused some reduction in the responses. When the preparation was stimulated transmurally with shocks of 200 msec duration at 1 shock/sec, the contractions were unaffected by any of the above drugs, except hemicholinium which again caused a slow reduction of up to 50% of the original response. It is concluded that nicotine, pempidine, hexamethonium, D-tubocurarine and hemicholinium probably block the response to stimulation of the hypogastric nerve by acting on peripheral ganglia in its pathway. Hemicholinium appears to have an additional effect in depressing the responses of the smooth muscle of the vas deferens to direct electrical stimulation, and procaine may act both on the ganglia and at the nerve terminals.

EEL ELECTROPLAQUES: SPIKE ELECTROGENESIS WITHOUT POTASSIUM ACTIVATION

Measurements with the voltage clamp technique demonstrate that only an early conductance increase occurs during spike electrogenesis of eel electroplaques. The delayed increase which is characteristic of spike electrogenesis in many other cells is absent. Instead, the membrane resistance increases two- to threefold above its resting value. The brief initial increase in conductance is due to sodium activation followed by rapid sodium inactivation. The influx of sodium causes an inward current of up to 80 ma/cm2. The inward current is abolished by eliminating the sodium from the normal medium (substitution of choline chloride for NaCl); by blocking sodium activation with tetrodotoxin; or by causing sodium inactivation through enrichment of the potassium in the medium. The delayed increase in membrane resistance is not affected by eliminating sodium influx, nor by substituting various impermeable anions for the chlorine of the normal medium. Thus, the increase in resistance signifies the occurrence of potassium inactivation which is unmasked by the absence of potassium activation.

SOME EFFECTS OF LONG CHAIN POLYMETHYLENE BISONIUM SALTS ON JUNCTIONAL TRANSMISSION IN THE PERIPHERAL NERVOUS SYSTEM

A survey has been made of the effects on junctional transmission of the complete series of polymethylene bis-trimethylammonium (BTM) and bis-triethylammonium (BTE) salts from the decamethylene compounds (BTM 10 and BTE 10) to those with twenty-one methylene groups in the chain. These were tested for their ability to cause contracture of the isolated chick biventer cervicis preparation, and for their ability to block the twitch responses of this preparation, those of the rat isolated diaphragm preparation, and those of the cat tibialis anterior preparation. They were also tested for their ability to block transmission in the cat superior cervical ganglion, to block the actions of acetylcholine on the guinea-pig isolated ileum, and for ability to inhibit the hydrolysis of acetylcholine by acetylcholinesterase. Their electrical conductivity has been measured in aqueous solution. Ability to cause contracture of the chick biventer cervicis is confined to the compounds BTM 10 to 15; BTE 10, 11 and 12 have some weak activity but the other BTE compounds, and the BTM compounds with more than fifteen methylene groups, have virtually no activity. In the BTE series both neuromuscular blocking and ganglion-blocking activities increase with chain length up to a maximum in the region of BTE 15 to 17 and then decline. In the BTM series ganglion-blocking activity increases with chain length in much the same way as in the BTE series, though the maximum activity is at a slightly longer chain length. At the neuromuscular junction an increase in chain length beyond BTM 10 leads to a decline in activity but this returns to some extent at longer chain lengths, reaching a second maximum at BTM 18, above which it declines further. At the ganglion BTE 16 is only slightly more active than BTM 16 and about five-times as active as hexamethonium; at the neuromuscular junction in the cat BTE 16 is about five-times as active as BTM 16 and about eight-times as active as (+)-tubocurarine. The affinity of the BTE compounds for the postganglionic acetylcholine receptors of the guinea-pig ileum reaches a maximum at BTE 14 but does not decline significantly with further increase in chain length. Anticholinesterase activity, likewise, does not alter significantly between BTM 12 and BTM 21 and the activity of the compounds in the BTE series appears to be similar. This property could conceivably be modifying the actions of some of the intermediate compounds but is not likely to be affecting those of the more active ones. The conductivity experiments indicate that micelle formation could be limiting the actions of the compounds with 20 or 21 methylene groups, but is not likely to be affecting those of the other compounds. The results suggest that there is a regular increase with chain length of the affinity of these compounds for the receptors in the ganglia and at the neuromuscular junction but that efficacy in causing contracture is limited to compounds with three methyl groups in the cationic head and a chain of about ten methylene groups. The connexion between this ability to depolarize and the ability to block transmission by desensitization is discussed.