Worm Breeder's Gazette 1(1): 20b

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Electrophysiological Studies of Ascaris Muscle

D. Weisblat, L. Byerly, R.L. Russell

Using Ascaris as a model system, we are studying ionic mechanisms of 
the spontaneous electrical activity in nematode somatic muscle.  The 
fast spike potentials appear to be Ca+2 mediated; their amplitude 
depends on the external Ca+2 concentration, they are TTX insensitive, 
they persist when Na+ is replaced by Tris+, choline+, or Cs+, and they 
are blocked by Co+2 and La+3.
When the normal solution is replaced by one containing 11 mM Ba+2 
and 0.15 mM Ca+2 as the only divalent cations, the slow waves 
underlying the normal spike activity appear to increase dramatically 
in amplitude and duration; spike activity gradually disappears.  The 
duration and amplitude of the slow waves at steady state under these 
conditions increase with Ba+2 concentration, reaching values of 1-2 
minutes and 50-60 mV, respectively, in 26 mM Ba+2.  These results and 
others lead us to conclude that the slow waves are also Ca+2 mediated.
The muscles are depolarized by 0.1 mM ouabain, suggesting some 
involvement of an electrogenic pump in maintaining the membrane 
potential.  TEA, in concentrations as low as 1 mM, has pronounced 
effects on the spontaneous myogenic activity, consistent with the 
effects observed when TEA is injected iontophoretically into C.