Effect of hibernation and noradrenaline on the resting state of neuromuscular junction of golden hamster (Mesocricetus auratus).

Abstract

1. The frequency of miniature end-plate potentials (m.e.p.p.s) and sensitivity to acetylcholine (ACh) of muscle fibres were studied in the diaphragm of awake and hibernating golden hamsters at 20–22°C. 2. The mean m.e.p.p. frequency was significantly lower in hibernating animals than in awake ones; mean values being 0.08±0.02/sec and 0.51±0.21/sec, respectively. 3. Addition of noradrenaline (NA) into the perfusion medium (final oncentration of NA 10−5 w/v) had no effect on the m.e.p.p. frequency. 4. Increased osmolality of the perfusion medium by 240% increased tempothan six hundred times in hibernating ones, respectively. During application of a hypertonic solution as well as after washing it out the difference in m.e.p.p. frequency bot groups of preparations disappeared. 5. Resting potentials of muscle fibres from hibernating and awake animals did not differ. Bath-applied NA (10−5 w/v) increased resting potentials consistently by about 10% in both groups. 6. The total length of the ACh-sensitive zone of muscle fibres was twice as great in hibernating animals as in awake ones (mean values being 1250±270 μm and 570±110 μm, respectively). Similarly the maximal sensitivity of muscle libres to iontophoretically applied ACh was twice as high in hibernating animals.