Behavioural and neuropathological effects produced by tetanus toxin injected into the hippocampus of rats

The behavioural effects of tetanus toxin, injected into the rostral hippocampus, have been studied in rats. A single dose (1000 mouse minimum lethal doses; n = 10) of the toxin produced tail rigidity, hunched back and sound- and touch-evoked stimuli, 48 hr after the injection in all rats treated and these culminated in generalized convulsions 5-7 days later. Seizures were also observed 4 days after the injection of 2000 MLDs (n = 10), whereas a dose of 500 MLDs (n = 10) was ineffective. Similarly, dose- and time-dependent lethal effects were observed. In comparison to the contralateral (untreated) hippocampus, tetanus toxin (1000 MLDs; n = 3) produced a statistically significantly reduction in the number of cells in the CA1 pyramidal cell layer of the injected side, 7 and 10 days after the injection. No changes were observed in other sectors (CA2 and CA3 areas) of the hippocampus. In conclusion, the present experiments have shown that the focal injection of tetanus toxin into the hippocampus produced dose- and time-dependent behavioural stimulation and lethal effects in rats.

Isolation and characterization of a novel human monoclonal antibody that neutralizes tetanus toxin

A human monoclonal antibody, designated 53-2-4, has been isolated and characterized in terms of its ability to interact with clostridial neurotoxins. In enzyme-linked immunosorbent assay assays the antibody reacted with native tetanus toxin, tetanus toxoid and the C fragment obtained from the carboxyterminus of the toxin (AA 864-1314). The antibody did not react with the B fragment of tetanus toxin (AA 1-863) or with six serotypes of botulinum neurotoxin (A to F). Both culture supernatant from the clonal line producing the antibody as well as homogeneous protein obtained by affinity purification of the antibody neutralized tetanus toxin. When tested in vivo, the antibody provided complete production against a supralethal injection of toxin; when tested in vitro, the antibody produced at least 99% inactivation of a 1 x 10(-9) M solution of toxin. The exceptional neutralizing activity of the antibody was attributed to its high affinity for the toxin (4.2 x 10(-10) mol/liter). Animal experiments revealed a novel phenomenon that has been labeled delayed intoxication. At the appropriate ratio of antibody to antigen, the toxin was retained in the host in a latent form. After several days the biological activity of the toxin became apparent and there was onset of nervous system poisoning. Isolated tissue experiments showed that each antibody molecule is capable of associating with two antigen molecules. The antibody has greater neutralizing activity when mixed with free toxin than when mixed with toxin already bound to plasma membrane receptors.

Preparation of affinity-purified, biotinylated tetanus toxin, and characterization and localization of cell surface binding sites on nerve growth factor-treated PC12 cells

Biotinylated derivatives of tetanus toxin were prepared and isolated by chromatofocusing and ganglioside-affinity chromatography. Biotinylation was monitored by the appearance of a 210,00 dalton complex upon SDS-polyacrylamide gel electrophoresis in the presence of avidin, and by selective binding to an avidin-Sepharose gel. At molar biotin:toxin ratios from 1:1 to 20:1 only biotinylated derivatives with low toxicity were obtained; these derivatives, however, retained 60-80% of their specific binding affinity for brain synaptosomes. A biotinylated tetanus toxin derivative purified by ganglioside-affinity chromatography was used to identify and localize tetanus toxin binding sites on PC12 cells. Electron microscopic analysis with streptavidin-gold revealed very low levels of tetanus toxin binding sites on the surface of untreated cells, and the appearance of such binding sites during the second week of nerve growth factor-induced differentiation. Examination of micrographs of the differentiated cells indicated that the tetanus toxin binding sites sites are concentrated on the neurites, with relatively few appearing on the cell bodies. Cognate studies using 125I-labeled, affinity-purified tetanus toxin revealed an increase in PC12 binding capacity from about 0.07 nmol/mg protein in untreated cells to 0.8 nmoles/mg protein in cells treated for 14 days with nerve growth factor. Cells treated in suspension for 2-3 weeks with nerve growth factor do not express tetanus toxin binding sites; upon plating, these cells required one week for the appearance of binding sites, although neurites grew much more rapidly from these "primed" cells. The high binding capacity of these tetanus toxin sites, as well as their sensitivity to neuraminidase, is indicative of a polysialoganglioside structure. The advantages of biotinylated tetanus toxin derivatives are discussed and the significance of nerve growth factor-differentiated PC12 cells grown as monolayers as a model for the study of the development, localization, and function of neuraminidase-sensitive tetanus toxin binding sites is presented.

Isolation, purification, and characterization of fragment B, the NH2-terminal half of the heavy chain of tetanus toxin

Fragment B, the N-terminal half of the heavy chain, an important domain of the tetanus neurotoxin molecule, was isolated for the first time. Tetanus toxin (composed of three domains, A, B, and C) was prepared from culture filtrates. Fragment A-B, derived from the toxin treated mildly with papain, was used for the isolation of fragment B. Fragment A-B obtained was dissociated into fragments A and B by reduction with 100 mM dithiothreitol and treatment with 2 M urea. Fragment B was separated from fragment A by ion-exchange column chromatography on a Mono Q column equilibrated with 20 mM Tris hydrochloride buffer (pH 7.6), containing 1 mM dithiothreitol and 2 M urea, in a fast-protein liquid chromatography system by elution with a linear gradient of 0 to 0.5 M NaCl. Fragment B was obtained in two forms having molecular weights of 48,000 +/- 2,000, which were indistinguishable by sodium dodecyl sulfate-gel electrophoresis or antigenic specificity, but distinguishable on polyacrylamide gel electrophoresis without sodium dodecyl sulfate and on isoelectric focusing (pI 6.7 and 7.3). The recovery of fragment B was 50 to 72% of that of fragment A-B on a molar basis. Purified fragment B was not toxic to mice on intravenous or intramuscular injection at doses of up to 100 micrograms, but was found to form channels (ca. 2.3 pS) in a lipid bilayer membrane by a patch clamp technique. The role of domain B of the tetanus toxin molecule in the mechanism of action of the toxin is discussed.

Inactivation of botulinum and tetanus toxins by chelators

Purified type A botulinum toxin of about 10(6) mouse 50% lethal doses per ml was greater than 99.9% inactivated when incubated at pH 7.4 for 30 min at 37 degrees C in 20 mM 1,10-phenanthroline (PTL) or 2,2'-dipyridyl (DPD) and was 96% inactivated when incubated in 70 mM 8-hydroxyquinoline-5-sulfonic acid (HQL), but was not affected when incubated in 200 mM EDTA. When used as a representative of the chelating agents, PTL inactivated greater than or equal to 99.9% of toxicity in the culture filtrate of C. botulinum type A, B, and E strains. Highly purified tetanus toxin at 2.5 x 10(5) 50% lethal doses per ml lost all toxicity in 40 mM PTL or 150 mM DPD but was not detectably affected by 100 mM HQL (the highest concentration possible). Toxin inactivation by 20 mM PTL was completely blocked when the PTL was prereacted with an equimolar amount of Zn2+ and significantly reduced when it was preincubated with one-third its molar amount of Fe2+. DPD at 20 mM had little toxin-inactivating potency when preincubated with an equimolar amount of Zn2+ and only some of this potency when preincubated with an equimolar amount of Fe2+. Toxicity was not recovered by adding Zn2+ or Fe2+ to PTL-treated toxin. Neutron activation analysis of type A toxin showed that for each toxin molecule present, there was 1 atom of Fe, 0.4 atom of Zn, and 22 to 55 atoms each of Ca and Mg. The biological activity of botulinum toxin seems to depend on a metal component, which is likely to be Fe.

Chronic epileptic foci in vitro in hippocampal slices from rats with the tetanus toxin epileptic syndrome

1. Minute doses of tetanus toxin were injected into the hippocampi of rats, under pentobarbitone anesthesia, to induce a chronic experimental epilepsy. The effects of this treatment were studied in vitro in hippocampal slices prepared 1-60 days after injection. 2. Epileptic activity was preserved in these slices in vitro, closely resembling that seen in vivo. Epileptiform afterdischarges were evoked by stimulation after survival times of greater than or equal to 3 days from injection. Spontaneous synchronous epileptic discharges were recorded from 7 days after injection. Both kinds of epileptiform activity were found with survival times up to 36 days but not beyond 44 days. This time course resembles the waxing and waning of the epileptic syndrome in vivo. 3. Two distinct types of spontaneous burst were seen. The first was a simple burst lasting 100-300 ms, reminiscent of the "interictal spike" of the clinical electroencephalogram. The second was much more prolonged, lasting several seconds. It consisted of a simple burst followed by a series of discrete afterbursts at 3-6/s and resembled the early stages of an epileptic seizure. Both types of burst were associated with slow field potentials that were positive at the cell-body layer. 4. Both the interictal and the seizure-like spontaneous epileptic discharges originated in the CA3b/c pyramidal cell region and propagated at 0.1-0.25 m/s along the cell layer toward the CA1 region. They occurred at very variable intervals, ranging from 20 s to 30 min. 5. Spontaneous epileptic bursts occurred in media containing 3 mM [K+]o to 5 mM in one-third of experiments during the period 1-4 wk after injection. Spontaneous bursts could be induced by increasing [K+]o to 5 mM in two-thirds of the remaining slices, which initially had produced evoked afterdischarges. 6. Intracellular recordings revealed that spontaneous field bursts were invariably associated with paroxysmal depolarization shifts (PDSs) and bursts of action potentials, suggesting that almost all the pyramidal cells in the region were recruited into the epileptic discharges. In some cells, smaller abnormal depolarizations were also seen; they were clearly larger than the spontaneous synaptic potentials but were not associated with field potentials. They may have been due to a more limited recruitment of pyramidal cells into partially synchronous bursts. 7. The tetanus toxin experimental epileptic syndrome differs from chronic models described previously in retaining in the hippocampal slice in vitro much of the spontaneous epileptic activity seen in vivo in the freely moving chronically epileptic rat.(ABSTRACT TRUNCATED AT 400 WORDS)

Chains and fragments of tetanus toxin. Separation, reassociation and pharmacological properties

Tetanus toxin, as obtained from bacterial culture filtrates, consists of two chains. Since their roles in poisoning are unknown, we have made a detailed study of their preparation, reassociation and pharmacological activity. 1. Two-chain tetanus toxin (pI 6.0) was subjected to isoelectric focussing under reducing conditions in 2M urea. Both light (pI 4.8) and heavy (pI 7.2) chains separated as nearly homogeneous proteins of low toxicities. Upon removal of urea and reoxidation, partial homodimerization by formation of disulfide bonds took place in the purified fractions. The toxin was reconstituted nearly quantitatively by covalent heterodimerization of the complementary chains, as shown by SDS/gel electrophoresis, toxicity studies, inhibition of evoked [3H]noradrenaline release and binding to rat brain membranes. 2. Accordingly, fragment B (pI 5.6) resulting from papain hydrolysis, was separated into a light chain and the N-terminal moiety of the heavy chain, called fragment beta 2 (pI 7.1 and 6.8, two maxima). Removal of urea and reoxidation led to reconstitution of fragment B. Covalent linkage did not occur between the two parts of the heavy chain, or between the light chain and the C-terminal part of the heavy chain. 3. The heavy chain alone inhibited K+-evoked [3H]noradrenaline release from a rat brain homogenate. However, the concentration-response ratio was flat and 10-100-fold higher concentrations were required than with native or reconstituted two-chain toxin. The light chain was inactive. Purified heavy chain but not light chain decreased the [3H]noradrenaline content, whereas the two-chain toxin increased it. Binding to rat brain membranes was assessed by competition with 125I-labelled two-chain toxin. In hypotonic buffer, the heavy chain, the papain fragment C and native and reconstituted two-chain toxin had comparable affinities to membranes. In isotonic buffer the heavy chain displayed an about 1000-fold lower affinity than native or reconstituted two-chain toxin. The light chain did not bind to membranes in either test. Our data indicate that (a) the light chain and the N-terminal part of the heavy chain are held together not only by one disulfide bond but also by hydrogen bonds and ionic forces to yield a two-chain toxin or fragment B and (b) both chains contribute to the actions of the toxin in vivo and in vitro, and to its binding.

Isolation and purification by high performance liquid chromatography of a tetanus toxin fragment (fragment [A-B]) derived from mildly papain-treated toxin

Fragment [A-B] of tetanus toxin was highly purified by combination of gel permeation chromatography, adsorption chromatography in an HPLC and immunoadsorption chromatography using anti-Fragment [C] as a ligand. The purified Fragment [A-B] (200 micrograms) elicited a peculiar toxicity, 'hypoactivity' or 'weakness', and killed the mice in ca. 73 hr and 88 hr when it was injected i.v. and i.m., respectively. However, contamination by the whole toxin was not detectable, in the purified fragment preparation, when up to 600 micrograms was tested by the mouse toxicity assay.

Presynaptic inhibition of the monosynaptic reflex during local tetanus in the cat

Tetanus toxin at doses of 2-2000 mouse MLD/kg was injected into the gastrocnemius muscle of the left hind limb of the cat. Acute experiments were performed at various times thereafter, when the intoxicated hind leg was strongly extended. Presynaptic inhibition of the monosynaptic reflex (MSR) of gastrocnemius motoneurones was tested by applying conditioning single electric stimuli to the antagonistic deep peroneal nerve. In most intoxicated animals the delayed inhibition of the MSR could still be observed at time intervals typical for presynaptic inhibition. However, the amplitude of the MSR often showed a strong toxin-induced facilitation at about 30 msec after the conditioning stimulus which could mask the presynaptic inhibition and sometimes made it difficult to observe it at all. After spinal transection at the Th1 level the inhibition could be better observed in such cases. Further evidence for the resistance of the presynaptic inhibitory system against the tetanus toxin in the given dose range was given by recordings of distinct dorsal root potentials which were abolished, together with the MSR inhibition by i.v. injection of picrotoxin. It is concluded that the mechanism of presynaptic inhibition remains intact or is even lengthened during local tetanus after i.m. injection of moderate, clinically relevant, toxin doses.

Tetanus toxin: biochemical and pharmacological comparison between its protoxin and some isotoxins obtained by limited proteolysis

Single-chain tetanus toxin (toxin S) was prepared from short-term cultures by lysis under protection with protease inhibitors, precipitation with 40% ammonium sulfate, gel filtration, and chromatography on DEAE ion exchanger. Its limited proteolysis by trypsin, post-arginine cleaving enzyme from mouse submaxillary gland and clostripain led to bichainal derivatives (BT, BA, BCl) consisting of a heavy chain and a larger version of the light chain. The latter was then converted by trypsin into a small version which comigrated with the light chain of bichainal extracellular toxin (BE). The light chain produced by chymotrypsin (BC) and elastase (BE1) was of intermediate size. The nick region serves as substrate for all esteroproteases investigated and comprises between one and two kDa. Limited proteolysis increased the hydrophilicity (BT greater than BE greater than S) in hydrophobic interaction HPLC, and anionic behaviour (BC greater than BE greater than BT greater than S) in DEAE ion exchanger HPLC. The bichainal toxins assessed (BC, BE or BT) were about two times more toxic than toxin S (LD50, mouse s.c. 2 ng/kg vs. 4 ng/kg). They were five to twelve times more potent than toxin S in three in vitro assays measuring the prevention of neurotransmitter release, i.e. on the phrenic nerve-hemidiaphragm preparation of the mouse (acetylcholine, with toxin BE and BT), on primary brain cell cultures from the mouse ([3H]noradrenaline, with toxin BE and BT), and on brain homogenate from rats ([3H]noradrenaline, with toxin BA, BC, BE and BT). Thus single-chain toxin is a less potent precursor of, or protoxin for, various bichainal isotoxins.(ABSTRACT TRUNCATED AT 250 WORDS)

Defining a region on tetanus toxin responsible for neuromuscular blockade

Administering high doses of tetanus toxin to animals produces neuromuscular blockade. Previous studies, in which specific F(ab) antibody fragments were used to mask the 50,000 MW COOH-terminal portion of the heavy chain (fragment c) on the toxin molecule, have shown that the paralyzing effect of the toxin was most probably located in an area comprising the light chain and the 50,000 MW NH2-terminal portion of the heavy chain (Fragment Ibc). In our study, the toxin was also complexed with F(ab) fragments directed to the light chain (alpha), heavy chain (beta), beta minus IIc, and with monoclonal antibodies to epitopes on IIc and beta minus IIc. Investigating the effect of the resulting complexes both in mice and on the sphincter pupillae muscle in rabbits permitted us to circumscribe further the tetanus toxin neuromuscular blocking activity in a region of the NH2-terminal fragment (Mr = 50,000) of the heavy chain (fragment beta minus IIc). Our results are consistent with the assumption that the beta minus IIc fragment is critical for the neuromuscular blockade activity of tetanus toxin. However, it cannot be ruled out that both the peripheral and central effects of the toxin result from the same portion of the toxin molecule, the nature of the action depending on where the toxin is carried after its introduction into the organism.

Distinct sites of action of clostridial neurotoxins revealed by double-poisoning of mouse motor nerve terminals

(1) We investigated the effects of single- and double-poisoning with tetanus toxin (TeTx), botulinum neurotoxin type A (BoTx A) and botulinum neurotoxin type B (BoTx B) on spontaneous and nerve-evoked quantal transmitter release at motor endplates of the triangularis sterni preparation of the mouse. (2) Inhibitory effects of TeTx and BoTx B on spontaneous and nerve-evoked transmitter release were very similar, except that the action of BoTx B required 500-fold lower concentrations and was less dependent on temperature. BoTx A caused stronger inhibition of quantal release than TeTx or BoTx B, but was comparatively much easier counteracted by 4-aminopyridine (4-AP). (3) In contrast to BoTx A, with TeTx or BoTx B the increase of transmitter release following onset of 50 Hz nerve stimulation was delayed for a few seconds and synaptic latencies of quanta showed large variations. This release pattern was also evident in all double-poisoning experiments, regardless of intoxication sequence. (4) Inhibition of evoked release was found to be slightly stronger with TeTx than with BoTx B, so the amount of nerve-evoked quanta released after double-poisoning with any sequence of these toxins always approached that of TeTx. In no case supra-additive actions were observed. (5) A strong reduction of evoked quanta was observed when BoTx A was applied in addition to either of the two other toxins. With reversed poisoning sequences (BoTx A - TeTx or BoTx A - BoTx B) the resulting values remained at the extremely low level of BoTx A. (6) In the presence of 4-AP double-poisoning with any combination between BoTx A and TeTx or BoTx B (regardless of intoxication sequence) revealed supra-additive effects, since the number of quanta released was considerably lower than that obtained with any of the toxins alone (in the presence of 4-AP). (7) Our results indicate that tetanus toxin and botulinum toxin type B have a common site of action which is different and independent from that of botulinum toxin type A.

Tetanus intoxication causes an increment of serotonin in the central nervous system

Mice injected with tetanus toxin (TTx) showed an increase of 5-hydroxytryptamine (serotonin, 5-HT) levels in the central nervous system. The increment was not uniform throughout the central nervous system. Particularly significant were the 25% and 80% increases observed, respectively, in whole brain and spinal cord. The levels of dopamine and norepinephrine remained unchanged. The subsequent studies of 5-HT turnover revealed a synthesis rate in the tetanic animals that was almost double that of controls. The degradation rate of the amine as well as the levels of 5-hydroxyindolacetic acid were unaffected.

A preclinical evaluation of aminopyridines as putative therapeutic agents in the treatment of botulism

4-Aminopyridine and 3,4-diaminopyridine were evaluated for their abilities to delay the onset of paralysis due to botulinum neurotoxin types A, B, and E. Experiments were done on phrenic nerve-hemidiaphragm preparations excised from mice. At a concentration that produced an enhancement in muscle twitch amplitude, 4-aminopyridine and 3,4-diaminopyridine delayed the onset of paralysis due to botulinum toxin type A. Under the same conditions, the drugs did little to protect tissues against botulinum toxin types B and E. 3,4-Diaminopyridine was also evaluated for its ability to reverse the paralysis due to botulinum toxin. Experiments were done on rat phrenic nerve-hemidiaphragm preparations that had previously been poisoned in vivo. The drug produced transient increases in neuromuscular transmission, with the effect being greater for botulinum neurotoxin type A than for botulinum neurotoxin types B and E. Equivalent types of experiments were done with tetanus toxin. The results with 3,4-diaminopyridine showed that tetanus toxin resembled botulinum toxin types B and E. The data help to clarify the role of aminopyridines as therapeutic agents in the treatment of botulism. They also provide insights into the mechanism of action of clostridial neurotoxins.

[Characteristics of the immune response of inoculated and intact animals to the administration of toxigenic and nontoxigenic strains of Clostridium tetani]

In experiments on guinea pigs the immune reactions of the animals immunized and not immunized against tetanus in response to the injection of C. tetani spores were studied. In the immunized animals an increase in the production of tetanus antitoxin, the development of delayed hypersensitivity and the activation of the mechanisms of cell-mediated immunity were observed. The nonimmunized animals showed specific changes in the T-system of immunity without the appearance of the clinical symptoms of tetanus, which is, probably, one of the mechanisms of natural immunity.

Protection of mice against tetanus toxin by combination of two human monoclonal antibodies recognizing distinct epitopes on the toxin molecule

Human B-lymphocytes were fused with the human lymphoblastoid B-cell line WI-L2-729 HF2. Hybridoma frequencies were in the range of 10(-5) when the mononuclear cells were (a) prestimulated with pokeweed mitogen (PWM), (b) fused with polyethyleneglycol (PEG), and (c) selected in a hypoxanthine-azaserine (HAza) containing medium. To generate monoclonal antibodies (MAb) specific for tetanus toxin (TToxin) human spleen cells were precultured with PWM plus tetanus toxoid (TToxoid) in two separate fusions. Two hybridomas were selected based on high binding activity using an enzyme-linked immunosorbent assay (ELISA) for TToxoid. Both hybridomas, cloned twice and designated anti-TT1 and anti-TT2, exhibited a near tetraploid karyotype and showed stable production of antibody (0.15 micrograms/ml) over several months. Using ELISA for fragments of TToxin and the immunoblotting technique, the two IgG1 monoclonal antibodies were found to bind to the heavy chain portion of the B-fragment (anti-TT1) and on the C-fragment (anti-TT2) of the toxin. When tested in an ELISA with TToxin the combination of anti-TT1 and anti-TT2 showed higher binding activity than either reagent alone. In an in vivo neutralization assay mice were completely protected against TToxin by the combination of the two antibodies while either antibody alone resulted only in a delay of death of the mice. These findings demonstrate that a cocktail of appropriate human monoclonal antibodies can be far superior to a single reagent when used in a therapeutic setting.

[Production of tetanolysin preparations and characteristics of their properties]

As the result of the study of tetanolysin-producing Clostridium tetani strains, their populations have been found to be markedly heterogeneous with respect to the hemolytic activity of clone cultures. On the basis of normal and dialyzed cultures of selected variants with maximum activity the preparations of tetanolysin have been obtained, and their hemolytic activity and antigenic properties have been studied. Antihemolytic rabbit sera have also been obtained and characterized. Partially purified preparations of tetanolysin with high hemolytic activity have been obtained by the fractionation of C. tetani dialyzed cultures with ammonium sulfate.

Interaction of solid-phase gangliosides with tetanus toxin and toxoid

Tetanus toxin has been fractionated on a column of silica beads coated with a ganglioside mixture. Toxicity and affinity of the fractions for brain membranes increased with their affinity for the column. The toxicity recovered with the nonabsorbed fraction was less than 5% with respect to the unfractionated toxin or its firmly bound moiety. Tetanus toxoid yielded less toxic or nontoxic fractions with different affinities for the column. Accordingly, binding of tetanus toxoid to brain membranes was partially preserved under mild toxoiding with formaldehyde. It is concluded that binding to gangliosides is a necessary, but not a sufficient, precondition for the pharmacological activity of tetanus toxin and its derivatives.

Botulism and tetanus: selected epidemiologic and microbiologic aspects

Botulism is rare in both developing and developed countries. During 1980 only 89 cases (18 food borne, 68 infant, 2 wound, 1 unspecified) were reported in the United States. Coproexamination is essential for laboratory confirmation of infant botulism. Botulinal antitoxins of equine origin are used for treating food-borne and wound botulism but are usually not recommended for infant cases. Tetanus is much more common in some developing countries than in developed countries. During 1980 only 95 cases of tetanus were reported in the United States; in 68 (72%) of these cases, the patient was 50 years or older, and in only two (2.1%) cases was the patient younger than one year. Tetanus neonatorum is a major problem in some developing countries. Diagnosis of tetanus is based primarily on clinical findings, but laboratory studies can be helpful, especially in epidemiologic investigations. Human hyperimmune immunoglobulin is now used in the treatment of tetanus.

Transmitter release in tetanus and botulinum A toxin-poisoned mammalian motor endplates and its dependence on nerve stimulation and temperature

The effects of tetanus toxin (TeTx) and botulinum A toxin (BoTx) on spontaneous and nerve-evoked transmitter release have been compared in mouse hemidiaphragms poisoned in vitro. At 37 degrees C endplates poisoned with either of these agents were characterized by (1) a decrease of miniature endplate potential (m.e.p.p.)-frequency to less than 30/min for TeTx and 3/min for BoTx, (2) reduced mean m.e.p.p.-amplitude and (3) 100% failure to show endplate potentials (e.p.p.s) in response to single nerve stimuli. In addition (4) tetanic nerve stimulation and/or reduction of temperature to about 20 degrees C caused a remarkable increase in the nerve-evoked transmitter release, but did not affect the low frequency of spontaneous m.e.p.p.s. However, several important differences exist between the effects of both toxins. (1) At room temperature even single nerve stimuli could elicit e.p.p.s in BoTx-muscles the failure rate being about 80%. For TeTx the failure was 100%. However, if the nerve was stimulated with higher frequencies (greater than 5 Hz), the probability of quantal release increased, the delay for release from the onset of stimulation being several seconds and similar to that observed at 37 degrees C. (2) TeTx distorted the synchronous release of quanta increasing the distribution of their synaptic delays. BoTx did not influence the time course of the phasic secretion process in response to nerve action potentials. (3) TeTx preferentially blocked the release of spontaneous m.e.p.p.s of large amplitude without affecting the frequency of the small amplitude ones, while BoTx inhibited both the small and large amplitude m.e.p.p.s. The distribution of the amplitudes of the nerve-evoked m.e.p.p.s were similar to those of spontaneous m.e.p.p.s before the blockade with the toxins.(ABSTRACT TRUNCATED AT 250 WORDS)

Different neuropathological effects of intrahippocampal injections of kainic acid and tetanus toxin

Behavioral and neuroanatomical effects of hippocampal injections of kainic acid (KA) and tetanus toxin (TT) were investigated in rats. Injections of KA resulted in both local and distant neuroanatomical damage, but not in clear signs of epilepsy; injections of TT on the other hand were followed (in some of the rats) by prolonged seizure attacks, but not by neuronal damage. Based on these results it is suggested that the widespread neuronal damage following KA lesions cannot be primarily attributed to orthodromic activation of epileptic discharges. Instead, specific properties of KA and their interactions with certain transmitters may provoke widespread neuroanatomical damage.