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Author Notes:

Address for correspondence: J. M. Weiss, Ph.D., Emory University School of Medicine, Emory West Campus, Building A, Room 510-N, 1256 Briarcliff Road, N.E., Atlanta, GA 30306, USA. Phone: 404-712-9771, Fax: 404-712-9755, Email: jweis01@emory.edu

Mirtazapine (Remeron) was generously provided by Organon, West Orange, NJ, USA.

We thank Dr Michael Owens of Emory University for his help in preparing the paroxetine and escitalopram used in these studies.

Statement of Interest: None


Research Funding:

This research was supported by Public Health Service grants MH65737 and MH79794.


  • Electrophysiology
  • locus coeruleus
  • mirtazapine
  • SSRI
  • tricyclic

Antidepressant drugs with differing pharmacological actions decrease activity of locus coeruleus neurons


Journal Title:

International Journal of Neuropsychopharmacology


Volume 12, Number 5


, Pages 627-641

Type of Work:

Article | Post-print: After Peer Review


Previous studies suggest that all effective antidepressant (AD) drugs decrease activity of locus coeruleus (LC) neurons. However, little data exist regarding blood levels of drug in these studies, and what data do exist suggest blood levels might have been very high. To assess whether decreased LC activity is produced by drugs that selectively block reuptake for either norepinephrine or serotonin at therapeutically relevant blood levels, effects of chronic administration of desipramine, paroxetine, and escitalopram on LC activity were measured across a range of doses and blood levels of drug. Further, effects of a range of doses of mirtazapine were examined; in that mirtazapine blocks α2 adrenergic receptors, it might be anticipated to increase rather than decrease LC activity. Finally, to begin to assess whether the response of LC to ADs was specific to these drugs, effects of four non-AD drugs (single dose) were measured. Drugs were administered via osmotic minipump for 14 d. Electrophysiological recording of LC activity (assessment of both spontaneous firing rate and sensory-evoked ‘burst’ firing) then took place under isoflurane anaesthesia on the last day of drug treatment. The blood level of drugs present at the end of the recording session was also measured. All AD drugs tested decreased LC spontaneous and sensory-evoked ‘burst’ firing, and this was observed across a wide range of blood levels for the drugs. Non-AD drugs did not decrease LC activity. The findings of this investigation continue to support the possibility that all effective AD drugs decrease LC activity.

Copyright information:

© 2008 CINP

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