Action of tetanus toxin in the cerebral cortex

Injection of more than ten mouse lethal doses of tetanus toxin into cat's motor cortex produces seizures accompanied by cortical electrical convulsive discharges. During the hours preceding onset of large seizures, "antidromic" inhibition of evoked cortical activity is reduced. The similarity of these effects to those observed in spinal cord suggests operation of similar inhibitory transmitters in the two parts of the central nervous system.

A comparison between the effects of a tetanus and the effects of sympathomimetic amines on fast- and slow-contracting mammalian muscles

The effects of adrenaline and isoprenaline on the tension and time-course of the contractions of the tibialis anterior and soleus muscles of cats and rabbits have been compared with the effects of previous high-frequency stimulation. Like a tetanus, adrenaline possessed a facilitating action on neuromuscular transmission and an action exerted directly on the muscle fibres. Isoprenaline possessed only the second of these two actions. The effect of adrenaline and isoprenaline on the muscle fibres was blocked by dichloroisoprenaline and by 1-(2 naphthyl)-2-isopropylaminoethanol, whereas the effect of adrenaline on neuromuscular transmission was blocked by phentolamine and by phenoxybenzamine. In the soleus muscle, both the catechol amines and a previous tetanus caused similar decreases in maximal twitch tension and in the times to peak tension and to half-relaxation. The muscle action potentials were unaltered or slightly increased in amplitude. In the tibialis anterior muscle, a previous tetanus and the catechol amines caused an increase in twitch tension and an increase in the overall duration of the twitch. The muscle action potentials were either unchanged or were slightly decreased in amplitude. In this muscle the effect of a tetanus differed from that of the catechol amines in that the large post-tetanic change was associated with a marked increase in the rate of rise of twitch tension.

THE INFLUENCE OF MINERAL CARRIERS ON THE SIMULTANEOUS ACTIVE AND PASSIVE IMMUNIZATION OF GUINEA-PIGS AGAINST TETANUS

Guinea-pigs given two doses of 2–25 Lf of fluid tetanus toxoid at 28 days interval had very satisfactory antitoxin titres 10 days after the second dose of toxoid (g.m. 28–2 units/ml.). Similar groups of animals given 150 units of horse tetanus antitoxin simultaneously with the first dose of toxoid responded very badly (g.m. < 0·016).

Interference by passive antitoxin occurred even when the antitoxin was given as late as 4 days after the first dose of toxoid.

Interference by passively administered antitoxin was minimal when aluminium hydroxide-adsorbed toxoid was used. It was necessary to increase the dose of antitoxin from 150 to 2400 units before significant interference occurred.

The route of administration of antitoxin did not significantly affect the results except when the antitoxin was given intravenously.

When guinea-pigs were immunized and bled at regular intervals it was found that with both fluid and aluminium hydroxide-adsorbed preparations, titratable antitoxin was present on the 14th day. The increase in titre thereafter was more rapid with the adsorbed preparation, but after a second dose of toxoid there was no significant difference in titre.

Passively administered antitoxin virtually abolished the active response to fluid toxoid, but with aluminium hydroxide-adsorbed preparations the primary response was not abolished but reduced and delayed and there was much individual variation.

Horse serum-sensitive guinea-pigs given adsorbed toxoid with simultaneous passive horse antitoxin gave a better primary response to the toxoid than did unsensitive animals.

The effectiveness of adsorbed tetanus toxoid in the simultaneous immunization procedure was directly related to the concentration of aluminium hydroxide or phosphate used: this concentration was critical and amounts below a certain level were ineffective. Calcium phosphate used as an adsorbent was unsatisfactory in this way, although it was an excellent adsorbent.

Investigation of the adsorbent characteristics of aluminium hydroxide and phosphate and of calcium phosphate, showed that the calcium salt on a molar basis was the most effective and that aluminium phosphate was the least effective.

Elution of toxoid from centrifuged precipitates of the three types of adsorbent showed that only 5% of toxoid was removed from the aluminium hydroxide, 13–18% from the calcium phosphate and 31–33% from the aluminium phosphate preparation when incubated with normal serum at 37° C.

Aluminium hydroxide adsorption in vitro interfered with the ability of antitoxin to combine with toxoid and to a lesser extent calcium phosphate had the same effect; aluminium phosphate, however, did not appear to interfere at all in this way

Histological observations on the tissue response to aluminium phosphate and calcium phosphate indicated that the typical alum granuloma produced by aluminium phosphate was not produced by the calcium salt.

SIMULTANEOUS ACTIVE AND PASSIVE IMMUNIZATION OF GUINEA-PIGS AGAINST TETANUS

1. Simultaneous active and passive immunization of guinea-pigs using tetanus toxoid adsorbed on to aluminium hydroxide produced a higher antitoxin response than simultaneous immunization using plain toxoid. The response was also better than that produced by plain toxoid alone.

2. A 24 hr. interval between the injection of plain toxoid and the subsequent injection of antitoxin gave no better results than when toxoid and antitoxin were given at the same time.

3. The response to simultaneous immunization, using adsorbed toxoid, of guinea-pigs sensitized to horse serum, was superior in the first 6 weeks to that of guinea-pigs which had not been sensitized.

4. The suggestion that simultaneous active and passive immunization of man should be performed with adsorbed toxoid rather than plain toxoid is supported by these results.