Glutamatergic channels in locust muscle show a wide time range of desensitization and resensitization characteristics.
Outside-out patches of membrane were excised from locust muscle. 10 mM L-glutamate applied to such patches in short pulses elicited rapidly a peak of channel opening, followed by desensitization with time constants between 1 ms and 20 ms for different channel subtypes. Slowly rising glutamate concentrations could produce almost complete desensitization without any channel openings. Desensitization thus proceeds from a closed channel state, prior to channel opening. Resensitization, i.e. recovery from desensitization, was tested by applying pairs of glutamate pulses, varying the pulse interval. Resensitization has a biphasic time course. While in rapidly desensitizing channels more than 50% of resensitization was achieved within a few milliseconds, in slowly desensitizing channels resensitization took seconds.
Physiologisches Institut, Technischen Universität München, F.R.G.
J
J
Dudel
C
C
Franke
H
H
Hatt
R L
RL
Ramsey
P N
PN
Usherwood
D000818:Animals; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D006110:Grasshoppers; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials; D009132:Muscles / Q000187:drug effects / Q000502:physiology*
D005971:Glutamates; D007473:Ion Channels; D018698:Glutamic Acid