Selective @entity308 of medium-latency leg and foot muscle responses to stretch by an alpha 2-agonist in XXXX .

@entity1 @entity717 @entity308 @entity21819
1. In standing @entity1 , toe-up rotation of a platform induces a short-latency (SLR) and a medium-latency response (MLR) in both soleus (Sol) and flexor digitorum brevis (FDB) muscles. Toe-down rotation evokes a MLR in the tibialis anterior (TA). The SLR is the counterpart of the monosynaptic stretch reflex, but the origin of the MLR is still debated. By means of @entity21819 (an alpha 2-adrenergic receptor agonist) we tested the hypothesis that the MLR is relayed by group II afferent fibres, since animal data indicate that @entity21819 or stimulation of monoaminergic brainstem centres decrease the excitability of spinal interneurones supplied by those fibres. In addition, we compared the effect of the drug on these responses with that induced by stabilization of posture. 2. Eight subjects received @entity21819 (150 micrograms kg-1 orally) or placebo, in a single-blind design. @entity717 were delivered prior to administration and for 3 h afterwards. Both TA- and FDB-MLRs decreased in size, starting from about 1 h after @entity21819 administration. Sol-SLR was unaffected. Response latencies were unchanged. Placebo induced no changes in any response. In each subject, the extent of TA-MLR @entity308 induced by holding onto a frame and by @entity21819 was superimposable. 3. The selective effect of @entity21819 on MLR supports the notion that it is relayed through group II afferent fibres. The similar effects of holding and @entity21819 on the response suggests that it is modulated by monoaminergic centres.
