Blockade of ionotropic receptor responses by progesterone in the ganglion cells of Aplysia.
To compare nongenomic effects of progesterone on various receptor responses of neurons, Aplysia ganglion cells were pretreated with 30 microM progesterone for 5 min and various receptor responses were tested using a conventional voltage-clamp method. Progesterone reduced nicotinic receptor-activated Na(+)-currents, nicotinic receptor-activated Cl(-)-currents, gamma-aminobutyric acid receptor-activated Cl(-)-currents, and dopamine receptor-activated Na(+)-currents. These depressant effects are similar at two different agonist concentrations. On the other hand, progesterone affected neither muscarinic receptor-activated K(+)-currents nor dopamine receptor-activated K(+)-currents. The former four types of receptors are known to be ionotropic while the latter two types of receptors are known to be metabotropic. Therefore, progesterone selectively inhibited all the types of ionotropic receptor responses, presumably in a noncompetitive manner.
Takashima
Koichiro
K
Department of Physiology, School of Medicine, Iwate Medical University, Morioka, Japan. ktakasim@iwate-med.ac.jp
Kawasaki
Satoshi
S
Kimura
Shingo
S
Fujita
Reiko
R
Sasaki
Kazuhiko
K
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001048:Aplysia; D018118:Chloride Channels / Q000502:physiology*; D004298:Dopamine / Q000494:pharmacology; D004553:Electric Conductivity; D005724:Ganglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D009474:Neurons / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011374:Progesterone / Q000494:pharmacology*; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology*; D018079:Receptors, GABA / Q000187:drug effects / Q000502:physiology*; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000502:physiology*; D015222:Sodium Channels / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018118:Chloride Channels; D011954:Receptors, Dopamine; D018079:Receptors, GABA; D011978:Receptors, Nicotinic; D015222:Sodium Channels; D011374:Progesterone; D005680:gamma-Aminobutyric Acid; D000109:Acetylcholine; D004298:Dopamine