title: Electric activity of rat anterior pituitary cells in vitro.
abstract: Regenerative responses were seen in most cells either after cessation of an inward current pulse or during an outward current pulse. Two cell groups were distinguished electrophysiologically. Type I cells showed action potentials with maximum rate of rise of 21.2+/-9.0 V/sec (mean+/-S.D., n=19), while type II cells generated small graded depolarising responses with maximum rate of rise less than 3 V/s. The resting potentials of type I and II cells were 31.8+/-14.9 mV (n=19) and 41.7+/-9.8 mV (n=31), respectively. The steady-state current/voltage relationship was linear for both cell types when the membrane potential was more negative than -60 mV. An outward rectification appeared when the membrane potential was more positive than -40 mV. The input resistance was smaller in type I cells (274+/-212 Momega, n=19) than in type II cells (1 112+/-456 Momega, n=16). Even in Na-free solution regenerative responses were observed in most cells. When the Ca2+ concentration was increased tenfold to 24 mM, the maximum rate of rise of the off-response increased from 1.9+/-0.8 V/s (n=11) to 5.7+/-2.12 V/s (n=5). All-or-none action potentials could be evoked in this Ca2+ rich solution. Action potentials of similar maximum rate of rise could be evoked after replacing 24 mM Ca2+ with isomolar Sr2+. Prolonged action potentials were seen after subsitution of Ca2+ for Ba2+. It is concluded that action potentials in most anterior pituitary cells have a Ca component, which in type I cells is additional to a Na component.
mesh_terms: D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000502:physiology; D005071:Evoked Potentials; D005260:Female; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000502:physiology*; D051381:Rats; D012964:Sodium / Q000502:physiology
chemical_list: D012964:Sodium; D002118:Calcium