Presynaptic inhibition compared with homosynaptic depression as an explanation for soleus H-reflex depression in humans.
The H-reflex is depressed for seconds if elicited following a single H-reflex or train of H-reflexes. Presynaptic inhibition from flexor afferents (tibialis anterior) onto soleus Ia afferents elicited by either single or trains of stimuli had no effect on the soleus H-reflex on a time scale of seconds. Postsynaptic inhibition was also excluded by magnetic stimulation tests that showed that the excitability of the motoneuron pool was not changed at latencies within a range of seconds. Homosynaptic depression localized at the presynaptic terminal seems to be the mechanism behind the H-reflex depression in humans.
Kohn
A F
AF
National Institutes of Health, NINDS, Human Motor Control Section, USA. andfkohn@leb.usp.br
Floeter
M K
MK
Hallett
M
M
D000328:Adult; D004558:Electric Stimulation; D004574:Electromagnetic Fields; D004576:Electromyography; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D010543:Peroneal Nerve / Q000502:physiology; D017661:Receptors, Presynaptic / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D013979:Tibial Nerve / Q000502:physiology
D017661:Receptors, Presynaptic