Sustained Exposure to 3,4-Methylenedioxymethamphetamine Induces the Augmentation of Exocytotic Serotonin Release in Rat Organotypic Raphe Slice Cultures

Abstract

Abstract. 3,4-Methylenedioxymethamphetamine (MDMA) causes serotonin efflux via serotonin transporter. Recently, we have reported that sustained exposure to MDMA induced an augmentation of serotonin release in rat raphe serotonergic slice cultures. Here we investigated the mechanism of augmented serotonin release from the slice cultures. Sustained MDMA exposure had no effect on MDMA-induced serotonin efflux in the synaptosomal fraction, whereas either tetrodotoxin, calcium channel inhibitors, or AMPA-receptor antagonists significantly attenuated the augmented serotonin release. These results suggest that the increase in Ca 2+ -dependent exocytotic serotonin release is mediated through activation of AMPA receptors and responsible for the sustained MDMA-induced augmentation of serotonin release.

Utility of organotypic raphe slice cultures to investigate the effects of sustained exposure to selective 5‐HT reuptake inhibitors on 5‐HT release

“…We previously reported that acute treatment with MDMA and methamphetamine induced a large increase in 5‐HT release in the same slice culture system (Higuchi et al ., 2008; Nagayasu et al ., 2010). Unlike SSRIs, MDMA and methamphetamine are substrate‐type releasers, which are transported into the nerve terminals and cause rapid 5‐HT release via a reverse transport‐mediated mechanism (Howell and Kimmel, 2008).…”

“…However, because our raphe slice cultures were maintained for 14–16 days in culture medium containing tryptophan (10 mg·mL −1 ), the tissue contents of 5‐HT and 5‐HIAA were maintained. Furthermore, we have shown that the slice cultures have functional 5‐HTergic neurons with the ability to release 5‐HT in response to stimulation, and are able to reuptake 5‐HT through SERT (Higuchi et al ., 2008; Nagayasu et al ., 2010). Taken together, these findings suggest that the raphe slice cultures are suitable for the analysis of the mechanisms underlying 5‐HTergic neural plasticity following sustained exposure to SSRIs in vitro .…”

“…The organotypic slice cultures retain neural and synaptic functions which enable analysis over a relatively long time and may offer advantages in analysis of the neural and molecular mechanisms underlying antidepressant efficacy of chronic treatment with SSRIs. As previously described (Higuchi et al ., 2008; Nagayasu et al ., 2010), we have established an organotypic slice culture, using tissue from the raphe nuclei. These raphe slice cultures exhibit 5‐HT biosynthesis and contain 5‐HT and its metabolite 5‐HIAA, at approximately the same or slightly higher levels than those previously reported in the raphe nucleus of adult rats (Cransac et al ., 1996).…”

“…In the mammalian brain, the principal source of the 5‐HTergic innervation of the forebrain is the dorsal and medial raphe nuclei located in the midbrain (Jacobs and Azmitia, 1992). Recently, we have established rat organotypic raphe slice cultures containing functional 5‐HTergic neurons, and have reported that sustained exposure to 3,4‐methylenedioxymethamphetamine (MDMA) and methamphetamine causes augmentation of 5‐HT release (Higuchi et al ., 2008; Nagayasu et al ., 2010). Thus, using raphe slice cultures, we can assess the effects of the acute and sustained exposure to SSRIs on the 5‐HTergic system in vitro .…”

Olanzapine augments the effect of selective serotonin reuptake inhibitors by suppressing GABAergic inhibition via antagonism of 5-HT6 receptors in the dorsal raphe nucleus

“…Therefore, we examined the effects of olanzapine on extracellular 5-HT levels in the organotypic raphe slice cultures that we had previously established (Higuchi et al, 2008;Nagayasu et al, 2010a). Q1 We also investigated the involvement of DRN GABAergic neurons and 5-HT receptors in the effects of olanzapine using organotypic raphe slice cultures and electrophysiological analysis in an acute raphe slice preparation.…”