Summary.
Using in vivo microdialysis in the freely moving rat we have examined the effects of 5-HT6 receptor antagonism on the neurochemical outcome of antidepressant treatment. Acute administration of both desipramine (10 mg/kg s.c.) and venlafaxine (10 mg/kg s.c.) produced a 2 fold increase in extracellular noradrenaline (NA) but no change in frontal cortex dopamine (DaA), 5-HT or glutamate. Fluoxetine (20 mg/kg s.c.) produced no change in extracellular levels of any of the neurotransmitters examined. SB-271046 produced a 3 fold increase in extracellular glutamate. Combination treatment of SB-271046 with each antidepressant produced no change in the antidepressant-induced changes in NA, DA or 5-HT. In contrast, both fluoxetine and venlafaxine attenuated the SB-271046-induced increase in extracellular glutamate, suggesting that 5-HT and possibly NA may be having an inhibitory action on the excitatory pathways enhanced by 5-HT6 receptor blockade. Furthermore, these data indicate that the neurochemical effects induced by NA and/or 5-HT reuptake inhibitors are not enhanced by 5-HT6 receptor blockade indicating that 5-HT6 receptor antagonists are unlikely to augment the therapeutic efficacy of these types of antidepressants.
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Received August 5, 2002; accepted January 13, 2003 Published online April 7, 2003
Authors' address: Dr. L. A. Dawson, Neuropharmacology (H30 1051), Psychiatry CEDD, Glaxo SmithKline, New Frontiers Science Park (North), Harlow, Essex, CM19 5AW, United Kingdom, e-mail: Lee_A_Dawson@gsk.com
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Dawson, L., Li, P. Effects of 5-HT6 receptor blockade on the neurochemical outcome of antidepressant treatment in the frontal cortex of the rat. J Neural Transm 110, 577–590 (2003). https://doi.org/10.1007/s00702-003-0812-1
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DOI: https://doi.org/10.1007/s00702-003-0812-1