Biochemical and behavioral effects of long-term citalopram administration and discontinuation in rats: role of serotonin synthesis.
We have investigated effects of continuous SSRI administration and abrupt discontinuation on biochemical and behavioral indices of rat brain serotonin function, and attempted to identify underlying mechanisms. Biochemistry of serotonin was assessed with brain tissue assays and microdialysis; behavior was assessed as the acoustic startle reflex. Long-term SSRI administration to rats reduced the content of 5-HT and its main metabolite shortly after inhibition of 5-HT synthesis in many brain areas with more than 50%. Turnover was not appreciably decreased, but significantly increased within 48h of drug discontinuation. The microdialysis experiments indicate that neuronal release of 5-HT depends strongly on new synthesis and emphasize the role of 5-HT(1B) receptors in the regulation of these processes. Discontinuation of the SSRI rapidly increased behavioral reactivity to the external stimulus. Additional startle experiments suggest that the increased reactivity is more likely related to the reduced extracellular 5-HT levels than to impaired synthesis. The combination of the marked reduction of serotonin content and limited synthesis may destabilize brain serotonin transmission during long-term SSRI treatment. These combined effects may compromise the efficacy of an SSRI therapy and facilitate behavioral changes following non-compliance.
Bosker
Fokko J
FJ
University Centre of Psychiatry, University Medical Centre Groningen, University of Groningen, The Netherlands. f.j.bosker@psy.umcg.nl
Tanke
Marit A C
MA
Jongsma
Minke E
ME
Cremers
Thomas I F H
TI
Jagtman
Evelien
E
Pietersen
Charmaine Y
CY
van der Hart
Marieke G C
MG
Gladkevich
Anatoliy V
AV
Kema
Ido P
IP
Westerink
Ben H C
BH
Korf
Jakob
J
den Boer
Johan A
JA
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects* / Q000502:physiology*; D001923:Brain Chemistry / Q000187:drug effects / Q000502:physiology; D015283:Citalopram / Q000494:pharmacology*; D003866:Depressive Disorder / Q000188:drug therapy / Q000378:metabolism / Q000523:psychology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000096:biosynthesis / Q000172:deficiency*; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology*; D013375:Substance Withdrawal Syndrome / Q000378:metabolism* / Q000523:psychology; D013997:Time Factors
D015283:Citalopram; D012701:Serotonin; D017367:Selective Serotonin Reuptake Inhibitors