Dual effects of thrombin and a 14-amino acid peptide agonist of the thrombin receptor on septal cholinergic neurons.
We have compared the effects of thrombin and of the 14-amino acid peptide agonist (TRAP-14) of the thrombin protease activated receptor (PAR) on cholinergic neurons in pure cultures of rat septal neurons and in co-cultures of septal neurons and glial cells. In pure septal cultures, low concentrations of thrombin (up to 10 nM) did not affect choline acetyltransferase (ChAT) activity, a marker of cholinergic neurons, or 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction, an index of cell viability. However, 100 nM thrombin decreased ChAT activity and MTT reduction by 44 and 17%, respectively. In co-cultures, a low concentration of thrombin (1 nM) increased ChAT activity (+75%), whereas a high concentration (100 nM) decreased it (-83%). At this high concentration, thrombin was neurotoxic, as indicated by a large decrease in MTT reduction (-80%). Thrombin effects on ChAT activity were mimicked by TRAP-14 both in pure septal cultures (no effect at 0.1 microM and -63% at 100 microM) and in co-cultures (+25% at 0.1 microM and -28% at 100 microM). In contrast, this peptide did not affect MTT reduction. These dual effects of thrombin and TRAP-14 on ChAT activity in co-cultures, were also observed on pure cultures of septal cells supplied with NGF. The activation and inhibition by TRAP-14 of the expression of ChAT activity in septal neuron/glial cell cultures were inhibited by a 9-amino acid peptide antagonist of thrombin PAR. Thus, the effects of thrombin on cholinergic neurons seem to be mainly mediated by thrombin PAR and glial cells seem to play a major role in these thrombin actions.
Debeir
T
T
CNS Research Department, Synthélabo Recherche, Bagneux, France.
Benavides
J
J
Vigé
X
X
D000109:Acetylcholine / Q000502:physiology; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002795:Choline O-Acetyltransferase / Q000378:metabolism*; D018920:Coculture Techniques; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian; D009414:Nerve Growth Factors / Q000494:pharmacology; D009457:Neuroglia / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009498:Neurotoxins / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018179:Receptors, Thrombin / Q000819:agonists / Q000502:physiology*; D013917:Thrombin / Q000494:pharmacology*
D009414:Nerve Growth Factors; D009498:Neurotoxins; D009842:Oligopeptides; D010446:Peptide Fragments; D018179:Receptors, Thrombin; C072032:thrombin receptor peptide (42-55); D002795:Choline O-Acetyltransferase; D013917:Thrombin; D000109:Acetylcholine