Exploring modulation of action potential firing by artificial graft of fast GABAergic autaptic afferences in hypophyseal neuroendocrine melanotrope cells.
Excitable cells are connected via electrical and chemical synapses to form a complex plastic network that transmit and modify action potential trains. In vivo and in vitro studies suggest that powerful type A GABAergic self-innervations, known as autapses, play a central role in the shaping of spike discharges. Herein, we have investigated the effects of artificial autaptic activity on action potential firing in cultured hypophyseal neuroendocrine melanotrope cells removed from any synaptic input. Type A autaptic conductances were introduced by using a dedicated dynamic-clamp device, based on a digital signal processor. The results indicate that cells grafted with autaptic dynamic-clamp are subjected to a modulation of both evoked firing and artificial GABA(A)-currents. The autaptic feedback reduced the action potentials amplitude, decreasing both the overshoot and the after-hyperpolarization potential (AHP). In return, the reduced voltage changes diminished the autaptic current amplitudes. The overall effect was a decrease of the cell firing rate. The introduction of a variable autaptic delay strongly altered the cell responses. Under certain conditions, the artificial autaptic current formed an additional component of the AHP which was markedly augmented. This action resulted in a stabilization of the action potential train leading to a more regular firing. In conclusion, it appeared that the autaptic feedback was very dependent on functional parameters such as the autaptic distance. Further investigations are in progress to complete our model, taking the autaptic plasticity into account.
Boussa
Sofiane
S
UPRES-EA, University of Le Havre, France. sofiane.boussa@univ-lehavre.fr
Pasquier
Jennifer
J
Leboulenger
François
F
Faure
Alain
A
Foll
Frank Le
FL
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001703:Biophysics; D002478:Cells, Cultured; D004558:Electric Stimulation / Q000379:methods; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology; D008297:Male; D052717:Melanotrophs / Q000187:drug effects / Q000502:physiology*; D008959:Models, Neurological; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D010902:Pituitary Gland / Q000166:cytology*; D011895:Rana ridibunda; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism* / Q000494:pharmacology
D005680:gamma-Aminobutyric Acid