Thrombin indirectly affects cholinergic cell expression in primary septal cell cultures in a manner distinct from nerve growth factor.
The effects of thrombin were examined in primary cultures of dissociated medial septal cells from fetal (embryonic day 17) rat brains. Seven days of continuous exposure of these cultures to thrombin produced a dose-dependent increase in the activity of the enzyme choline acetyltransferase (EC 2.3.1.6) and no change in the number of acetylcholinesterase (EC 3.1.1.7)-positive cells. Maximal induction of choline acetyltransferase activity occurred around 1-2 nM thrombin and was first detected after five days of treatment. In addition, thrombin promoted neuronal cell aggregation, proliferation of the astroglia, and changes in astroglial cell morphology. Neuronal aggregation was first noted after 24 h of treatment, while the proliferative response of the astroglia was first apparent after four days of treatment, slightly prior to the increase in choline acetyltransferase enzymatic activity. In order to see if the induction of the enzyme choline acetyltransferase was dependent upon the astroglial cell response, we included the anti-mitotic agent 5-fluoro-2'-deoxyuridine, to find that astrocyte proliferation, as well as thrombin-induced increase in choline acetyltransferase, were both abolished. In contrast, the aggregation of neurons was not affected. Finally, thrombin-induced changes in choline acetyltransferase could not be antagonized by immunoneutralizing anti-nerve growth factor antibodies and when thrombin was added simultaneously with 100 ng/ml 2.5-S nerve growth factor, the increase in choline acetyltransferase activity was additive. In conclusion, it appears that thrombin affects cholinergic septal neurons indirectly via the responsive astrocytes in a manner distinct from nerve growth factor.
Mazzoni
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IE
Centre de Recherche Pediatrique, Hôpital Ste Justine, Montréal, Québec, Canada.
Kenigsberg
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RL
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects; D015415:Biomarkers; D002449:Cell Aggregation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002795:Choline O-Acetyltransferase / Q000096:biosynthesis*; D004790:Enzyme Induction / Q000187:drug effects; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains / Q000196:embryology; D012688:Septum Pellucidum / Q000166:cytology / Q000187:drug effects* / Q000196:embryology; D013917:Thrombin / Q000494:pharmacology*
D015415:Biomarkers; D005904:Glial Fibrillary Acidic Protein; D009414:Nerve Growth Factors; D002795:Choline O-Acetyltransferase; D013917:Thrombin