Effects of tetanus toxin on spontaneous and evoked transmitter release at inhibitory and excitatory synapses in the rat SDCN neurons.
We observed the effects of tetanus toxin (TeNT) on spontaneous miniature and evoked postsynaptic currents at inhibitory (glycinergic) and excitatory (glutamatergic) synapses in SDCN of rat spinal cord, by use of 'synaptic bouton' preparations, under voltage clamp condition. TeNT (>10 pM) dose-dependently decreased the frequency without affecting amplitude of glycinergic spontaneous miniature IPSCs. However, TeNT (100 pM) had no effect on frequency or amplitude of glutamatergic spontaneous EPSCs. Focal paired electrical stimulation of 'synaptic boutons' elicited two consecutive glycinergic eIPSCs or glutamatergic eEPSCs with large amplitude and low failure rate (Rf). TeNT (100 pM) reduced the amplitude and increased the failure rate of the first glycinergic eIPSCs and greatly enhanced the ratio of the second to first (P2/P1) eIPSCs. Application of 4-AP restored glycinergic eIPSCs suppressed by TeNT (100 pM). However, TeNT (100 pM) had no effect on the amplitude, Rf or P2/P1 ratio of glutamatergic eEPSCs. These results show that TeNT pre-synaptically affects spontaneous and evoked, and inhibitory and excitatory neurotransmitter release differentially, thereby suggesting that molecular events underlying spontaneous and evoked, inhibitory and excitatory neurotransmitter release may be different in CNS, and that the release machinery becomes less sensitive to Ca²⁺ in TeNT poisoned 'synaptic boutons'.
Research Division for Life Sciences, Kumamoto Health Science University, 325 Izumi-machi, Kumamoto 861-5598, Japan.
Min-Chul
MC
Shin
Kiku
K
Nonaka
Masahito
M
Wakita
Toshitaka
T
Yamaga
Yasushi
Y
Torii
Tetsuhiro
T
Harakawa
Akihiro
A
Ginnaga
Yushi
Y
Ito
Norio
N
Akaike
D000818:Animals; D019274:Botulinum Toxins, Type A / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials; D018684:Glycine Agents / Q000494:pharmacology*; D055369:Miniature Postsynaptic Potentials; D009474:Neurons / Q000187:drug effects; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000187:drug effects; D013569:Synapses / Q000187:drug effects*; D013744:Tetanus Toxin / Q000494:pharmacology*
D018683:Excitatory Amino Acid Agents; D018684:Glycine Agents; D013744:Tetanus Toxin; D019274:Botulinum Toxins, Type A