Induction of c-FOS immunoreactivity in the hippocampus following potassium stimulation.
In microdialysis procedures high potassium ion concentrations are generally used to induce neurotransmitter release. However, the widespread effects, if any, of such a treatment have not been described. In order to establish a possible link between c-fos expression and stimulating conditions for neurotransmitter release in microdialysis procedures we administered KCl (100 mM) into the hippocampus. Proto-oncogene c-FOS-like immunoreactivity is upregulated in granule cells of the dentate gyrus, pyramidal cells of the hippocampus, cingulate, piriform and frontoparietal cortices at 2 h, but not 24 h after K+ administration. Neither implantation of the probes nor perfusion with artificial cerebrospinal fluid resulted in similar patterns of c-FOS immunoreactivity. In addition, we investigated whether the impairment of the cholinergic septohippocampal pathway would modify the K(+)-induced expression of the immediate early gene c-fos in the hippocampus. The expression of c-fos induced by KCl was not altered in the animals with fimbria-fornix lesion despite the marked decrease in acetylcholine release in the hippocampus. Glutamate concentrations measured in the same superfusates showed that a significantly greater glutamate release occurs in denervated hippocampi. Furthermore, abolishment of seizure-like activity (induced by KCl) in anesthetized animals did not alter expression of c-FOS immunoreactivity in the K(+)-stimulated hippocampi. The results from these studies confirm that most of the releasable acetylcholine of the hippocampus is linked to the fimbrial input and may suggest that c-FOS upregulation in this model does not respond to any cholinergic input from the medial septum via the fimbria-fornix.
Herrera
D G
DG
Department of Pharmacology and Therapeutics, Montreal, Canada.
Maysinger
D
D
Goiny
M
M
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003956:Dialysis; D005786:Gene Expression Regulation / Q000187:drug effects; D016762:Genes, fos / Q000276:immunology*; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D006624:Hippocampus / Q000033:anatomy & histology / Q000187:drug effects / Q000276:immunology*; D007150:Immunohistochemistry; D008297:Male; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013268:Stimulation, Chemical
D005971:Glutamates; D018698:Glutamic Acid; D000109:Acetylcholine; D011188:Potassium