Potassium-evoked neuronal release of serotonin in experimental chronic portal-systemic encephalopathy.
Portal-systemic encephalopathy (PSE) is associated with an increased brain tissue turnover of serotonin (5-HT). Despite increased 5-HT metabolism, brain 5-HT release in rats with a portacaval shunt (PCS) seems to be unaltered. Although this may indicate that the overall 5-HT output is unaltered in PSE, it is also possible that the 5-HT release pattern might be altered in some way. In the present study, the potassium-evoked frontal neocortical release of 5-HT was studied in experimental chronic PSE. KCI (60 mM) produced marked increases in the 5-HT output compared with basal values both in PCS and sham rats. Simultaneously, the KCI challenge resulted in significant elevations in the 5-HT release of PCS compared with sham. In Ca2+-free medium, the difference between PCS and sham rats in the KCl-evoked release of 5-HT was abolished. In the presence of TTX (1 mM), both groups displayed increased extracellular 5-HT levels. Again, a difference with higher amplitude of the 5-HT release in PCS compared with sham was evident. It is concluded that in experimental chronic PSE an augmented neocortical 5-HT release compared with the normal in vivo situation is available. The possible mechanism(s) responsible for the difference in neocortical 5-HT output between PCS and sham-operated rats in response to the KCl-challenge is discussed.
Bergqvist
P B
PB
Department of Clinical Pharmacology, Lund University Hospital, Sweden.
Hjorth
S
S
Apelqvist
G
G
Bengtsson
F
F
D000818:Animals; D001835:Body Weight; D002118:Calcium / Q000494:pharmacology; D002908:Chronic Disease; D005110:Extracellular Space / Q000378:metabolism; D005625:Frontal Lobe / Q000378:metabolism; D006501:Hepatic Encephalopathy / Q000378:metabolism* / Q000473:pathology; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008099:Liver / Q000473:pathology; D008297:Male; D017551:Microdialysis; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D009929:Organ Size; D011189:Potassium Chloride / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D012701:Serotonin; D013779:Tetrodotoxin; D006897:Hydroxyindoleacetic Acid; D011189:Potassium Chloride; D002118:Calcium