A series of experiments to characterize the neuromuscular transmission in Antarctic fishes (Pagothenia borchgrevinki) and the effects of temperature on these reactions

The low temperature adaptations involved in neuromuscular transmission in Antarctica fish was characterized. An exploratory dissection of Pagothenia borchgrevinki revealed that the inferior oblique ocular muscle was well suited for neuromuscular studies. Visual observations of contraction while stimulating the oculomotor was conducted and the interaction of stimulus frequency and temperature on muscle contraction was monitored. Electromyograms were used to record the muscle contraction at different temperatures and to assess the sensitivity of the neuromuscular junction to curare (tubocurarine - HCl). Photographic records of the EMG experiments were analysed.

A sequence of neurophysiological experiments were conducted to further characterize the neuromuscular transmission in fishes including:
a) Determination of optimum stimulation frequency and changes with temperature,
b) Dose response measurements of acetylcholine and changes with temperature,
c) Changes of the resting potential with temperature and
d) recording the spontaneous miniature end-plate potentials (MEPP) and temperature induced changes in MEPP size, frequency and rate of decay.

Brain and cranial nerves were dissected from five species of fish; P. borchgrevinki, Trematomus bernacchii, T. hansoni, Dissostichus mawsoni and Gymnodraco acuticeps, and preserved in methanol-acetic acid-formalin for anatomical, histological studies and lipid analysis. Glycerated muscle preparations of P. borchgrevinki eye muscles were made to analyse the myosin ATP-ase system responsible for the actual force of the contraction.