Reciprocal Ia inhibition between elbow flexors and extensors in the human.

Abstract

SUMMARY1. Reciprocal inhibition between elbow flexor and extensor muscles (biceps and triceps brachii) has been investigated in nine healthy subjects. Two techniques were used to assess changes in motoneurone excitability after stimulation of antagonist muscle afferents: (1) monosynaptic reflexes elicited by a mechanical stimulation of the distal muscle tendon (tendon tap); (2) post-stimulus time histograms (PSTH) of voluntarily activated motor units.2. Electrical stimulation of the antagonist muscle nerve produced a short-latency and short-lasting inhibition of the flexor and extensor motoneurones. The amount of this inhibition was found to be similar in both motor nuclei.3. The inhibition could be evoked with conditioning electrical stimuli as low as 0 7 x motor threshold (MT) or by very weak tendon taps applied to the antagonist tendon. In the former case the threshold of this inhibition was found to be consistently increased after raising the threshold of Ia afferent fibres by a longlasting muscle vibration. Since a contribution from cutaneous afferent fibres was ruled out, it is concluded that this inhibition was Ia in origin.4. Post-stimulus time histograms of voluntarily activated triceps and biceps motor units were made following electrical stimulation of homonymous and antagonist muscle afferents. This enabled an estimate of the central synaptic delay of the inhibitory process. An average central delay of 0-94 ms in excess of that of monosynaptic facilitation was found, thus suggesting that the inhibitory process could be mediated by only one interneurone. 5. A conditioning reflex discharge elicited in the antagonist muscle by a tendon tap depressed or suppressed this inhibition. This depression was maximal when the reflex discharge was elicited 10-20 ms before the conditioning stimulus for the inhibition and never lasted more than 30 ms. It is argued that the only mechanism compatible with such a depression is the inhibitory activity of Renshaw cells acting on the pathway mediating reciprocal inhibition.6. We conclude that group Ia afferent fibres from elbow extensor and flexor

Modulation of Brachioradialis Motoneuron Excitabilities by Group I Fibers of the Median Nerve in Humans

“…Facilitation and inhibition mediated by low threshold afferent fibers among muscles in the human upper limb have been studied (Baldissea et al 1983;Day et al 1984;Cavallari and Katz 1989;Katz et al 1991;Schieppati et al 1991;Cavallari et al 1992;Creange et al 1992;Rossi et al 1995;Aymard et al 1995;Naito et al 1996Naito et al , 1998aMarchard-Pauvert et al 2000;Naito 2003Naito , 2004aSuzuki et al 2005;Ogawa et al 2005;Wargon et al 2006;Sato et al 2006;Nakano et al 2006). The BB motoneurons receive monosynaptic facilitation of group Ia fibers from the extensor carpi radialis (ECR) and FCR, disynaptic inhibition of group Ia fibers from the triceps brachii (TB), and oligosynaptic inhibition of group I fibers from PT (Katz et al 1991;Cavallari et al 1992;Naito et al 1996, 1998a, Naito 2003, 2004a.…”

“…The BB motoneurons receive monosynaptic facilitation of group Ia fibers from the extensor carpi radialis (ECR) and FCR, disynaptic inhibition of group Ia fibers from the triceps brachii (TB), and oligosynaptic inhibition of group I fibers from PT (Katz et al 1991;Cavallari et al 1992;Naito et al 1996, 1998a, Naito 2003, 2004a. The BR motoneurons receive monosynaptic facilitation from group I fibers from ECR and oligosynaptic inhibition of group I fibers from …”

“…The cumulative sum technique (Ellaway 1978) was also employed for presentation of PSTHs. The discharges of a BR-MU were recorded with a pair of needle electrodes (Seirin Acupuncture Needle, Facilitatory (facilitation) or inhibitory effects (inhibition) of low threshold afferent fibers on excitabilities of motoneurons among muscles in the human upper limb have been studied (Baldissea et al 1983;Day et al 1984;Cavallari and Katz 1989;Katz et al 1991;Schieppati et al 1991;Cavallari et al 1992;Creange et al 1992;Rossi et al 1995;Aymard et al 1995;Naito et al 1996Naito et al , 1998aMarchard-Pauvert et al 2000;Naito 2003Naito , 2004aSuzuki et al 2005;Ogawa et al 2005;Wargon et al 2006;Sato et al 2006;Nakano et al 2006). Group I fibers from the muscle spindle (Ia) and Golgi tendon organ (Ib) are included in the afferent fibers.…”

“…To estimate the central synaptic delay of an effect, that is the excess of the central latency of the effect over that of the monosynaptic facilitation, the difference between the latencies of the effect after the MNE stimulation (L1) and a facilitatory effect after the homonymous BR nerve stimulation (BR homonymous facilitation: monosynaptic) (L2) in a BR-MU was measured in PSTHs (Katz et al 1991;Naito et al 1996, 2004a: Marchand-Pauvert et al 2000 (Fig. 1).…”

Functional Significance of Facilitation Between the Pronator Teres and Extensor Carpi Radialis in Humans: Studies with Electromyography and Electrical Neuromuscular Stimulation

“…1) (Aymard et al, 1995;Baldissea et al, 1983;Cavallari & Katz, 1989;Cavallari et al, 1992;Creange et al, 1992;Day et al, 1984;Fujii et al, 2001;Katz et al, 1991;Kobayashi et al, 2000;Lourenço et al, 2007;Marchand-Pauvert et al, 2000;Miyasaka et al, 1995Miyasaka et al, , 1996Miyasaka et al, , 1998Miyasaka et al, , 2007Naito et al, 1996Naito et al, , 1998aNaito et al, , 2001Naito, 2003Naito, , 2004Nakano et al, 2005Nakano et al, , 2006Ogawa et al, 2005;PierrotDeseilligny & Mazevet, 2000;Rossi et al, 1995;Sato et al, 2002;Shinozaki et al, 2001;Suzuki et al, 2005Suzuki et al, , 2007Wargon et al, 2006). These reflex arcs modulate motoneuron excitabilities to coordinate smooth muscular movements (Naito, 2003(Naito, , 2004Pierrot-Deseilligny et al, 1981;Rothwell, 1994;Tanaka, 1989).…”