title: Fast-activating voltage- and calcium-dependent potassium (BK) conductance promotes bursting in pituitary cells: a dynamic clamp study.
abstract: The electrical activity pattern of endocrine pituitary cells regulates their basal secretion level. Rat somatotrophs and lactotrophs exhibit spontaneous bursting and have high basal levels of hormone secretion, while gonadotrophs exhibit spontaneous spiking and have low basal hormone secretion. It has been proposed that the difference in electrical activity between bursting somatotrophs and spiking gonadotrophs is due to the presence of large conductance potassium (BK) channels on somatotrophs but not on gonadotrophs. This is one example where the role of an ion channel type may be clearly established. We demonstrate here that BK channels indeed promote bursting activity in pituitary cells. Blocking BK channels in bursting lacto-somatotroph GH4C1 cells changes their firing activity to spiking, while further adding an artificial BK conductance via dynamic clamp restores bursting. Importantly, this burst-promoting effect requires a relatively fast BK activation/deactivation, as predicted by computational models. We also show that adding a fast-activating BK conductance to spiking gonadotrophs converts the activity of these cells to bursting. Together, our results suggest that differences in BK channel expression may underlie the differences in electrical activity and basal hormone secretion levels among pituitary cell types and that the rapid rate of BK channel activation is key to its role in burst promotion.
authors.affiliation: Department of Biological Science and Department of Mathematics and Program in Neuroscience, Florida State University, Tallahassee, Florida 32306, USA. joel@neuro.fsu.edu
authors.forename: Joël
authors.initials: J
authors.lastname: Tabak
authors.forename: Maurizio
authors.initials: M
authors.lastname: Tomaiuolo
authors.forename: Arturo E
authors.initials: AE
authors.lastname: Gonzalez-Iglesias
authors.forename: Lorin S
authors.initials: LS
authors.lastname: Milescu
authors.forename: Richard
authors.initials: R
authors.lastname: Bertram
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D055592:Biophysical Phenomena / Q000187:drug effects / Q000502:physiology*; D001703:Biophysics; D002478:Cells, Cultured; D004553:Electric Conductivity; D005260:Female; D007211:Indoles / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000502:physiology*; D008954:Models, Biological; D017711:Nonlinear Dynamics; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D010902:Pituitary Gland / Q000166:cytology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D007211:Indoles; D051036:Large-Conductance Calcium-Activated Potassium Channels; D010455:Peptides; D026902:Potassium Channel Blockers; C048220:paxilline; C064719:iberiotoxin
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