PubMed Health⌕ Search

Biomedical subjects

R Penner

Publications and source records attributed to R Penner.

68 records · Page 4Linked to original sources
PubMed1984

Action of botulinum A toxin and tetanus toxin on synaptic transmission.

Intracellular recordings of the spontaneous activity from mammalian spinal cord neurons in culture demonstrated different sensitivities of excitatory and inhibitory synaptic transmission for the action of tetanus toxin (Tetx) and botulinum toxin type A (Botx). The effects of Tetx and Botx on spontaneous and nerve-evoked transmitter release were compared under identical experimental conditions in experiments on in vitro poisoned mouse diaphragms. At 37 degrees C completely paralyzed endplates are characterized by a very low frequency of spontaneous miniature endplate potentials (m.e.p.p.s) and by a 100% failure to evoke endplate potentials (e.p.p.s) in response to single nerve stimuli. Striking differences in the action of both toxins have been observed when the very low transmitter release probabilities of paralyzed nerve-muscle preparations were increased by tetanic nerve stimulation and/or application of potent K+-channel blockers and/or by reduction of temperature to 25 degrees C. While Botx did not change the short latency between nerve impulse and postsynaptic response, Tetx produced a temporal dispersion of the quantal release suggesting that the toxins act at different sites in the chain of events that result in transmitter release. To find further evidence to support the different actions of the toxins the spontaneous transmitter release was studied in more detail. Tetx blocked preferentially the release of so-called large mode m.e.p.p.s without affecting the frequency of the small mode ones. In contrast, Botx strongly inhibited both the small and large mode m.e.p.p.s.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMedDate not supplied

Intracellularly injected tetanus toxin inhibits exocytosis in bovine adrenal chromaffin cells.

The clostridial neurotoxins tetanus and botulinum toxin type A are known to block transmitter release from nerve terminals, probably by interfering with some essential process controlling exocytosis after the entry of Ca2+ ions. Although exocytosis occurs in many secretory cells, these toxins show a high specificity for neurones and the secretory response of cultured bovine adrenal medullary cells is not inhibited by exposure to medium containing tetanus or botulinum toxin type A (although it is by botulinum toxin type D). Here we report that when tetanus toxin and botulinum neurotoxin type A are injected intracellularly into chromaffin cells they strongly inhibit secretion, as revealed by the measurement of cell capacitance. These results indicate that these toxins are normally ineffective in chromaffin cells because they are not bound and internalized, so do not reach their site of action. Furthermore, we have localized the secretion-blocking effects of the toxin to a fragment comprising the light chain covalently linked to part of the heavy chain, suggesting that this part of the molecule contains the active site.

Adrenal Medulla↗