Membrane Biophysics and BiochemistryDifferent Ca2+ source for slow AHP in completely adapting and repetitive firing pyramidal neuronsPineda, J C.1,4; Galarraga, E2; Foehring, R C.3Author Information 1Centro de Investigaciones Regionales, Universidad Autonoma de Yucatan, Apdo. 9-37, Merida, Yuc. 97000 2Departamento de Biofisica, Instituto de Fisiologia Celular, Universidad Nacional Autonoma de Mexico, 04510 Mexico 3Department of Anatomy and Neurobiology, University of Tennessee, Memphis, TN 38163, USA. 4Corresponding Author: J. C. Pineda ACKNOWLEDGEMENTS: We are grateful to A. E. Stewart, S. D. Timmons, F. Alvarez-Cervera and J. L. Góngora for reading the manuscript and Birch Harms for excellent technical assistance. This work was supported by Conacyt, Mexico Grant 27325-N (CA) and NS33579 NINDS(2). Received 21 April 1999; accepted 30 April 1999 NeuroReport: June 23rd, 1999 - Volume 10 - Issue 9 - p 1951-1956 Buy Abstract INTRACELLULAR recordings in an in vitro neocortical slice preparation from immature rats were used to investigate the Ca2+ source for slow afterhyperpolarization (sAHP) generation in pyramidal neurons that exhibit complete spike frequency adaptation (CA neurons). In pyramidal neurons that maintain repetitive firing for long periods of time (RF neurons), N-, P- and Q-type Ca2+ channels supply Ca2+ for sAHP generation. In CA neurons, the sAHP was reduced by only 50% by the combination of antagonists for these Ca2+ channel types and L-type channels. Ryanodine and dantrolene, blockers of Ca2+ −induced Ca2+ release, reduced the sAHP by ∼45% in CA neurons, but caused no reduction of the sAHP in RF neurons. Dantrolene application caused CA neurons to fire throughout a 1 s suprathreshold current injection (as do RF neurons). © 1999 Lippincott Williams & Wilkins, Inc.