Skin desensitization by topical anesthesia was studied for its effect on the motoneuron excitability of the soleus muscle. Skin areas overlying calf, tibial, quadriceps and hamstrings muscles and skin dermatomes (L2, L3, L4, L5, S1 and S2) were studied separately. Motoneuron excitabilities were measured by the H-reflex and Achilles tendon reflex (for alpha and gamma motoneurons). It was shown t...

The postembryonic acquisition of behavior requires alterations in neuronal circuitry, which ultimately must be understood as specific changes in neuronal structure, membrane properties, and synaptic connectivity. This study addresses this goal by describing the postembryonic remodeling of the excitability and dendritic morphology of an identified motoneuron, MN5, which during the metamorphosis ...

Motoneurons often fire repetitively and for long periods. In sustained voluntary contractions the excitability of motoneurons declines. We provide the first detailed description of the time course of human motoneuron recovery after sustained activity at a constant discharge rate. We recorded the discharge of single motor units (MUs, n = 30) with intramuscular wire electrodes inserted in triceps...

Although it is known that noradrenaline (NA) powerfully controls spinal motor networks, few data are available regarding the noradrenergic (NAergic) modulation of intrinsic and synaptic properties of neurons in motor networks. Our work explores the cellular basis of NAergic modulation in the rat motor spinal cord. We first show that lumbar motoneurons express the three classes of adrenergic rec...

The relevance of putative contributors to age-related memory loss are poorly understood. The tail withdrawal circuit of the sea hare, a straightforward neural model, was used to investigate the aging characteristics of rudimentary learning. The simplicity of this neuronal circuit permits attribution of declines in the function of specific neurons to aging declines. Memory was impaired in advanc...

The excitability of the motoneuron (MN) pool in the resting state was compared between normal control subjects and patients with spasticity resulting from HTLV-I-associated myelopathy, using a new parameter, Hslp/Mslp, and the conventional parameters Hmax/Mmax and Hth/Mth. Differences in the excitability of the MN pool between these two groups reached a high degree of statistical significance o...

Nerve cells characteristically exhibit fluctuation in excitability. In the case of neurons lying within the central nervous system it is reasonable to suppose that multiple influences contribute to excitability fluctuation. Certain of these influences might depend upon factors intrinsic to individual nerve cells while others might be due to extrinsic factors. I t may be assumed that, among a gr...

The individual intrinsic excitability of the motoneuron pool was investigated by the H-reflex method. A Iinear regression line was calculated +.o be fitted to the recruitment curve of the H-reflex evoked at a range of electric stimulation lower than the threshold of the M-response. The slope of this regression line was found to be significantly invariant among repeated measurements within an in...