Immature maxi-K channels exhibit heterogeneous properties in the embryonic rat telencephalon.
Using the cell-attached configuration of the patch-clamp technique, we recorded large-conductance K channels (LCKs) from intact telencephala and cortical slices of embryonic (E) 12-14 and E21 rats, respectively. Conductance (about 200 pS with K(+)-rich pipettes), kinetics and sensitivity to fatty acids (FAs) were reminiscent of some features of the Ca-activated 'maxi-K' channel (BK), yet less than half the LCKs were Ca-sensitive. At E12-14, an even smaller proportion of the channels were strictly voltage-sensitive, that proportion rising to about 50% at E21. Ca and voltage sensitivities were observed independent of one another. The open probability of voltage-sensitive LCKs increased exponentially with depolarization rates similar to those reported for classical BKs. It is postulated that embryonic LCKs may constitute immature forms of BKs whose gating is regulated by endogenous FAs.
Bulan
E J
EJ
Laboratory of Neurophysiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Md 20892.
Barker
J L
JL
Mienville
J M
JM
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004553:Electric Conductivity; D004622:Embryo, Mammalian; D005314:Embryonic and Fetal Development; D005260:Female; D005865:Gestational Age; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D007700:Kinetics; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D019814:Myristic Acid; D009227:Myristic Acids / Q000494:pharmacology; D009474:Neurons / Q000502:physiology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013687:Telencephalon / Q000196:embryology / Q000502:physiology*; D013997:Time Factors
D008041:Linoleic Acids; D009227:Myristic Acids; D015221:Potassium Channels; D019814:Myristic Acid; D015124:8-Bromo Cyclic Adenosine Monophosphate; D016718:Arachidonic Acid; C016276:8-bromocyclic GMP; D000001:Calcimycin; D002110:Caffeine; D019787:Linoleic Acid; D006152:Cyclic GMP