Tetanus toxin inhibits the evoked outflow of an inhibitory (GABA) and an excitatory (D-aspartate) amino acid from particulate brain cortex.
In order to elucidate the mode of action of tetanus toxin, particles from rat forebrain were preloaded with tritiated GABA or D-aspartate, pre-incubated with tetanus toxin and then depolarized with K+, either in a batch procedure or by superfusion. The toxin depresses, but does not abolish, the evoked outflow of both amino acids in either system. Omission of Ca2+ decreases the outflow in the batch procedure by about 40%. The remaining outflow of either amino acid is insensitive to tetanus toxin, whereas the Ca2+ dependent outflow is completely inhibited. Antitoxin neutralizes the toxin but does not reverse its in vitro effects, once manifest. The toxin effects increase with time and temperature of pre-incubation. Pretreatment of the particles with V. cholerae neuraminidase, which is known to convert the long-chain gangliosides quantitatively into GM1, does not decrease the sensitivity to tetanus toxin. Besides particles from rat brain, those from chicken, but not those from frog brain, are toxin-sensitive when tested for GABA outflow in the batch procedure. Frog brain does not yield the typical ganglioside pattern, and also does not measurably bind 125I-tetanus toxin. The homoexchange diffusion of GABA, but not of D-aspartate, is slightly facilitated by tetanus toxin. We confirmed that tetanus toxin slightly inhibits the uptake of GABA, whereas that of D-aspartate is not measurably influenced. The accumulation, driven by a Na+/K+ gradient, of GABA into membrane vesicles from rat cortex is not affected by tetanus toxin. The present data support the hypothesis that tetanus toxin influences a process involved in the outflow of many transmitters, both excitatory and inhibitory.
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000032:analysis / Q000187:drug effects* / Q000378:metabolism; D002645:Chickens; D005260:Female; D005732:Gangliosides / Q000032:analysis; D066298:In Vitro Techniques; D009638:Norepinephrine / Q000378:metabolism; D011898:Ranidae; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity; D013696:Temperature; D013744:Tetanus Toxin / Q000633:toxicity*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D005732:Gangliosides; D013744:Tetanus Toxin; D001224:Aspartic Acid; D005680:gamma-Aminobutyric Acid; D002118:Calcium; D009638:Norepinephrine