A delayed all-or-none hyperpolarisation induced by a single Ca action potential in hamster eggs.
A transient change of membrane potential and resistance could be evoked after a long latency (ca. 9 s) by a single calcium action potential in some unfertilized hamster eggs. The estimated reversal potential for the delayed response was close to EK supporting the conclusion that K channels were opened indirectly by the Ca2+ influx through voltage-gated channels. A second action potential elicited after the first did not induce a similar response. A number of treatments (insertion of a Ca2+ pipette, application of Na+-free solution, La3+ or high external pH) likely to raise [Ca2+]i also induced similar large changes of potential and resistance after which a single action potential failed to evoke a large delayed response. The evidence indicates that a small rise in [Ca2+]i activates a slow process leading to a further large increase in [Ca2+]i.
McNiven
A I
AI
Department of Preclinical Veterinary Sciences, University of Edinburgh, Great Britain.
Yoshida
S
S
Georgiou
P
P
House
C R
CR
D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D006224:Cricetinae; D005260:Female; D066298:In Vitro Techniques; D008647:Mesocricetus; D010063:Ovum / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*
D015221:Potassium Channels; D002118:Calcium