Absence of effects of contralateral group I muscle afferents on presynaptic inhibition of Ia terminals in humans and cats

Author(s)

Mezzarane, Rinaldo Andre ^[1] ; Kohn, Andre Fabio ; Couto-Roldan, Erika ^[2] ; Martinez, Lourdes ^[3] ; Flores, Amira ^[4] ; Manjarrez, Elias ^[4]

Affiliation

^[1] Univ Sao Paulo, Escola Politecn, Biomed Engn Lab, EPUSP, PTC, BR-05424970 Sao Paulo - Brazil

^[2] Univ Manitoba, Spinal Cord Res Ctr, Winnipeg, MB - Canada

^[3] CINVESTAV IPN, Dept Neurociencias, Mexico City, DF - Mexico

^[4] Benemerita Univ Autonoma Puebla, Inst Fisiol, Puebla - Mexico

• Document type: Journal article
• Source: Journal of Neurophysiology; v. 108, n. 4, p. 1176-1185, AUG 2012.
• Web of Science Citations: 13

Abstract

Mezzarane RA, Kohn AF, Couto-Roldan E, Martinez L, Flores A, Manjarrez E. Absence of effects of contralateral group I muscle afferents on presynaptic inhibition of Ia terminals in humans and cats. J Neurophysiol 108: 1176-1185, 2012. First published June 6, 2012; doi:10.1152/jn.00831.2011.-Crossed effects from group I afferents on reflex excitability and their mechanisms of action are not yet well understood. The current view is that the influence is weak and takes place indirectly via oligosynaptic pathways. We examined possible contralateral effects from group I afferents on presynaptic inhibition of Ia terminals in humans and cats. In resting and seated human subjects the soleus (SO) H-reflex was conditioned by an electrical stimulus to the ipsilateral common peroneal nerve (CPN) to assess the level of presynaptic inhibition (PSI\_control). A brief conditioning vibratory stimulus was applied to the triceps surae tendon at the contralateral side (to activate preferentially Ia muscle afferents). The amplitude of the resulting H-reflex response (PSI\_conditioned) was compared to the H-reflex under PSI\_control, i.e., without the vibration. The interstimulus interval between the brief vibratory stimulus and the electrical shock to the CPN was -60 to 60 ms. The H-reflex conditioned by both stimuli did not differ from that conditioned exclusively by the ipsilateral CPN stimulation. In anesthetized cats, bilateral monosynaptic reflexes (MSRs) in the left and right L 7 ventral roots were recorded simultaneously. Conditioning stimulation applied to the contralateral group I posterior biceps and semitendinosus (PBSt) afferents at different time intervals (0-120 ms) did not have an effect on the ipsilateral gastrocnemius/soleus (GS) MSR. An additional experimental paradigm in the cat using contralateral tendon vibration, similar to that conducted in humans, was also performed. No significant differences between GS-MSRs conditioned by ipsilateral PBSt stimulus alone and those conditioned by both ipsilateral PBSt stimulus and contralateral tendon vibration were detected. The present results strongly suggest an absence of effects from contralateral group I fibers on the presynaptic mechanism of MSR modulation in relaxed humans and anesthetized cats. (AU)

• FAPESP's process: 10/15522-4 - Proposal of a mechanical stimulator for the study of synchronous bilateral fluctuations in reflex excitability of humans
• Grantee: Rinaldo André Mezzarane
• Support Opportunities: Scholarships in Brazil - Post-Doctoral