Reversible deafferentation of abducens motoneurons and internuclear neurons with tetanus neurotoxin.
Tetanus neurotoxin (TeNT) is a blocker of synaptic vesicle exocytosis in central synapses with preferential affinity for inhibitory neurotransmission. Following its intramuscular injection, TeNT is retrogradely and trans-synaptically transported towards the premotor terminals. Therefore, we have used TeNT as a tool to study the consequences of functional deafferentation on motoneurons following its peripheral administration. For this, we injected the toxin into the lateral rectus muscle at doses of 5 or 0.5 ng/kg and recorded the discharge activity of abducens motoneurons and internuclear neurons in the alert cat. Our results showed that: (i) TeNT blocked selectively the afferent inhibitory signals on abducens neurons only when used at a low dose, whereas both excitatory and inhibitory synaptic drive was lost after the high dose treatment; (ii) all effects were reversible within one month; and (iii) strikingly, the internuclear neurons of the abducens nucleus showed similar discharge alterations to the motoneurons, suggesting a TeNT action on shared common afferences.
González-Forero
D
D
Laboratorio de Neurociencia, Facultad de Biología, Universidad de Sevilla, Spain.
De La Cruz
R R
RR
Delgado-García
J M
JM
Pastor
A M
AM
D000010:Abducens Nerve / Q000166:cytology / Q000502:physiology*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002415:Cats; D005133:Eye Movements / Q000502:physiology; D007395:Interneurons / Q000187:drug effects* / Q000502:physiology; D008666:Metalloendopeptidases / Q000494:pharmacology*; D009046:Motor Neurons / Q000187:drug effects* / Q000502:physiology; D013563:Sympathectomy, Chemical / Q000379:methods*; D013744:Tetanus Toxin / Q000494:pharmacology*
D013744:Tetanus Toxin; C035979:tetanospasmin; D008666:Metalloendopeptidases