Effects of intracerebral injections of quinolinic acid on serotonergic neurons in the rat brain.
The effects of intrastriatal and intrahippocampal injections of the excitotoxic amino acid, quinolinic acid (QUIN), were examined in the rat using immunohistochemical and neurochemical techniques. Serotonin and 5-hydroxyindoleacetic acid measurements at 90 min, 6 h, 4 and 11 days following QUIN administration revealed highly elevated levels of the metabolite in the injected nuclei, with peak increases occurring after 4 days. Serotonin levels remained largely unchanged over the same time period. Direct visualization of hippocampal serotonergic fibers by immunohistochemistry demonstrated morphological changes (varicosities, swellings) in otherwise undamaged serotonin-positive afferents 4 days following a local QUIN injection. Hippocampal serotonin turnover was assessed at 4 days after an intrahippocampal QUIN-application: following inhibition of aromatic amino acid decarboxylase, the accumulation of 5-hydroxytryptophan was twice as rapid in QUIN-lesioned hippocampi as in controls. Dose-response relationships, examination of brain regions distant from the two injection sites and the temporal sequence of the changes described here suggest a close association between QUIN-induced neuronal degeneration and alterations in the serotonergic system.
Aldinio
C
C
Mazzari
S
S
Toffano
G
G
Köhler
C
C
Schwarcz
R
R
D000818:Animals; D001921:Brain / Q000166:cytology / Q000187:drug effects*; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D003342:Corpus Striatum / Q000201:enzymology / Q000378:metabolism; D005968:Glutamate Decarboxylase / Q000378:metabolism; D006624:Hippocampus / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D007267:Injections; D008297:Male; D009474:Neurons / Q000187:drug effects*; D011725:Pyridines / Q000494:pharmacology*; D017378:Quinolinic Acid; D011805:Quinolinic Acids / Q000276:immunology / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism / Q000502:physiology*
D011725:Pyridines; D011805:Quinolinic Acids; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D002795:Choline O-Acetyltransferase; D005968:Glutamate Decarboxylase; D017378:Quinolinic Acid