The Thermal Sensitivity of Purinergic Modulation of Contractile Activity of Locomotor and Respiratory Muscles in Mice

—We have previously demonstrated that hypothermia significantly modulates the effect of ATP on the contractile activities of various types of rodent locomotor muscles. The aim of this study was to compare the effects of ATP on contraction of mouse locomotor (m. soleus) and respiratory (m. Diafragma) muscles at normal and low temperatures. It has been found that a decrease in the ambient temperature to 22°C is associated with a decrease in the force of muscle contraction (m. Diafragma) induced by electrical stimulation and carbachol, as well as with an increase in the contractile force of m. soleus. The potentiating effects of ATP in these muscles are preserved even in response to temperature reduction, but they are enhanced only in carbachol-induced contractions, thus indicating a postsynaptic localization of a thermal sensitive element in purine modulation. The characteristic features of ATP release modulation with the predominant postsynaptic thermal sensitive link in different motor units in hypothermia in mice may underlie the adaptive mechanisms of this small rodent.