Wet mass, resting membrane potential, frequency of miniature end-plate potentials and the concentration of [3H]ouabain-binding sites were studied after 7 days' immobilization of the rat soleus and extensor digitorum longus (EDL) muscles in the shortened or stretched position and after 3 and 7 days of remobilization. We observed that the loss of muscle mass by 37% in the rat soleus immobilized for 7 days in the shortened position is accompanied by a membrane depolarization of about 5 mV, a decrease in frequency of miniature end-plate potentials by 60% and a decrease of [3H]ouabain binding by 25%. Only minor changes were found in stretched soleus and in shortened and stretched EDL. After 3 days of remobilization of stretched soleus the muscle mass, [3H]ouabain binding and miniature end-plate potential frequency recovered to control values but the resting membrane potential continued to decrease. All changes induced by immobilization disappeared on day 7 of remobilization.

• MeSH
• atrofie MeSH
• časové faktory MeSH
• imobilizace * MeSH
• inbrední kmeny potkanů MeSH
• krysa rodu Rattus MeSH
• membránové potenciály MeSH
• nervosvalová ploténka fyziologie   MeSH
• ouabain metabolismus   MeSH
• svalová kontrakce * MeSH
• svaly metabolismus   patologie   fyziologie   MeSH
• vazebná místa MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• ouabain MeSH

During the early postnatal period, the differentiation and maturation of muscle spindles in the rat is still dependent on their sensory innervation. When a nerve is crushed during this period, most spindles in the denervated muscles degenerate and after reinnervation only occasional spindles of atypical structure are to be found in these muscles. We determined the basic functional properties of these atypical spindles in adult rats and attempted to correlate them with their structural characteristics. The discharge rates of 13 afferent units from the soleus or lateral gastrocnemius muscles were evaluated in response to stretch. These units were capable of a slowly adapting response to 2-4 mm stretches. Their mean discharge frequencies at any point of the ramp-and-hold stretch were, however, on an average 50% lower than normal values. The conduction velocities of afferents from the atypical spindles were in the range of 10-40 m/s. Histological examinations revealed that 90% of the atypical muscle spindles found in the soleus or lateral gastrocnemius muscles had only 1 or 2 intrafusal fibres without any nuclear accumulations as compared to four intrafusal fibres in normal muscle spindles in the rat. The proportional decrease of the discharge rate in both the dynamic and static part of the response of these atypical spindles could be due to the decreased synaptic area between the sensory terminals and the intrafusal fibres and/or to altered structural properties of the intrafusal fibres.

• MeSH
• akční potenciály MeSH
• časové faktory MeSH
• denervace svalu * MeSH
• inbrední kmeny potkanů MeSH
• krysa rodu Rattus MeSH
• mechanoreceptory fyziologie   MeSH
• nervové vedení MeSH
• počet buněk MeSH
• rozdrcení nervu MeSH
• svaly cytologie   inervace   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH