Effect of atmospheric ions on hippocampal pyramidal neuron responsiveness to serotonin.
The effect of long-term exposure to positive or negative atmospheric ions on the responsiveness of rat forebrain neurons to serotonin (5-HT) was studied. Male Sprague-Dawley rats were exposed to positive or negative ions (1.5 X 10(6) ions/ml) for 21 days, and a third group of rats served as controls. Unitary extracellular recordings from pyramidal neurons of the CA1 and CA3 regions of the dorsal hippocampus were obtained under urethane anesthesia, and their responsiveness to microiontophoretically applied acetylcholine (ACh), norepinephrine (NE) and 5-HT was assessed. Spontaneous rate of discharge and sensitivity to NE and ACh of hippocampal neurons were not affected by exposure to atmospheric ions. Exposure to negative ions increased and that to positive ions decreased the responsiveness of these neurons to 5-HT. During the winter, a circadian rhythm of responsiveness to 5-HT was observed in the control group, sensitivity being lowest in the morning and highest in the evening. Exposure to ions disrupted this circadian rhythm; in rats exposed to negative ions, responsiveness throughout the day was similar to that observed in the evening in the controls, whereas in rats exposed to positive ions, the circadian rhythm of responsiveness to 5-HT was inverted. Brain concentrations of 5-HT, tryptophan, and 5-hydroxyindoleacetic acid were unchanged by exposure to atmospheric ions.
Dowdall
M
M
De Montigny
C
C
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001272:Atmosphere; D001923:Brain Chemistry; D002940:Circadian Rhythm; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D006897:Hydroxyindoleacetic Acid / Q000032:analysis; D007477:Ions; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D011712:Pyramidal Tracts / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012621:Seasons; D012701:Serotonin / Q000032:analysis / Q000494:pharmacology; D014364:Tryptophan / Q000032:analysis
D007477:Ions; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan; D000109:Acetylcholine; D009638:Norepinephrine