Acute Treatment with the Antidepressant Fluoxetine Internalizes 5-HT1A Autoreceptors and Reduces the In Vivo Binding of the PET Radioligand [18F]MPPF in the Nucleus Raphe Dorsalis of Rat

Neuronal Phenotype Dependency of Agonist-Induced Internalization of the 5-HT1ASerotonin Receptor

“…5, 6). Such a difference meets the in vivo data reported by Riad et al (2001) who showed that acute treatment with the SSRI fluoxetine induced 5-HT 1A R internalization (visualized by electron microscopy with specific antibodies) in dorsal raphe nucleus but not hippocampus in rats. In our studies, we were able to visualize a different level of internalization depending on the efficacy of agonists.…”

“…Studies from Riad et al (2001 using immunocytochemical labeling coupled to electron microscopy, provided evidence that SSRI treatment induced 5-HT 1A R internalization in neurons in the raphe but not in the hippocampus. However, only acute treatment but not chronic treatment with SSRIs apparently produced a decreased expression of 5-HT 1A R at the somatodendritic plasma membrane of DRN neurons (Riad et al, 2008), in sharp contradiction with the idea that receptor internalization could mediate, at least in part, chronic SSRI-induced functional desensitization demonstrated by electrophysiological recordings.…”

Antidepressants and Antipsychotic Drugs Colocalize with 5-HT3Receptors in Raft-Like Domains

“…For example, chronic administration of benzodiazepines induces internalization of the GABA A receptor (Tehrani and Barnes, 1997). Moreover, antidepressants (Koshikawa et al, 1987;Burgi et al, 2003;Riad et al, 2004) and antipsychotic drugs (Willins et al, 1999) may enhance receptor internalization/downregulation of 5-HT 1A receptors, 5-HT 2 receptors, or ␤-adrenoceptors (␤1AR), which all are G-protein-coupled receptors. However, only chronic treatment with DMI, but not acute doses of DMI, may cause downregulation of ␤1AR in vivo (Koshikawa et al, 1987;Burgi et al, 2003).…”

Effect of Increased Serotonin Levels on [18F]MPPF Binding in Rat Brain: Fenfluramine vs the Combination of Citalopram and Ketanserin

“…The reduction in the raphe may also be due to internalization of the 5-HT 1A receptor after agonist stimulation. Riad et al (2004) has shown that presynaptic receptors are internalized after agonist stimulation, whereas postsynaptic receptors are not.…”