Effects of furosemide on the resting membrane potentials and the transmitter-induced responses of the Aplysia ganglion cells.
Effects of Furosemide (FM) on the ionic channels in the ganglion cells of Aplysia were investigated using a conventional electrophysiological method. Application of 1 mM FM for 30 min did not alter the resting membrane potential or conductance. Na+-dependent responses to acetylcholine (ACh) were slightly depressed but Cl--dependent responses to ACh and gamma-aminobutyric acid (GABA) were markedly depressed by FM. On the other hand, K+-dependent responses to ACh and dopamine (DA), and cyclic adenosine-3', 5' monophosphate (cAMP)-dependent response to DA were not appreciably altered by 1 mM FM. The depressing effects of FM on both Na+- and Cl--dependent responses were due to the non-competitive inhibition of their receptor activities. It was concluded that 1 mM FM can change neither Na+-K+-pump nor Cl--pump mechanisms in the ganglion cells of Aplysia, but it depresses the receptor-operated Na+-and Cl--channel activities, the greater effect on the open Cl--channels. In addition, it was postulated that FM effect may be highly specific to the open state of Cl--channels, regardless of whether the membrane is excitable or not.
Nakai
K
K
Department of Physiology, School of Medicine, Iwate Medical University, Morioka.
Sasaki
K
K
Matsumoto
M
M
Takashima
K
K
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001048:Aplysia / Q000187:drug effects / Q000502:physiology*; D002712:Chlorides / Q000502:physiology; D004298:Dopamine / Q000494:pharmacology*; D005665:Furosemide / Q000494:pharmacology*; D005724:Ganglia / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000502:physiology; D012964:Sodium / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D002712:Chlorides; D005680:gamma-Aminobutyric Acid; D005665:Furosemide; D012964:Sodium; D000109:Acetylcholine; D011188:Potassium; D004298:Dopamine