Psychostimulants differentially regulate serotonin transporter expression in thalamocortical neurons

Area of Science:

• Neuroscience
• Developmental Biology
• Pharmacology

Background:

• Serotonin transporters (SERTs) are transiently expressed in developing thalamocortical neurons, allowing co-release of serotonin (5-HT).
• This expression is crucial for serotonergic modulation of neocortical circuits and offers a model for studying SERT regulation.

Purpose of the Study:

• To investigate if psychostimulants, acting as SERT agonists and antagonists, regulate the developmental expression of SERT in thalamocortical neurons.
• To understand the mechanisms underlying SERT regulation by psychostimulants.

Main Methods:

• Primary cultures of embryonic day 18 rat thalamocortical neurons were maintained until postnatal day 15 (P15).
• Neurons were treated with SERT substrates (5-HT, MDMA) or antagonists (fluoxetine, cocaine).
• SERT protein levels, expression time course, and subcellular localization were analyzed.

Main Results:

• In untreated cultures, SERT protein peaked at P3 and disappeared by P10.
• Chronic treatment with SERT substrates significantly increased peak SERT protein levels and prolonged expression, redistributing intracellular SERT to the plasma membrane.
• SERT antagonists reduced total SERT expression levels and altered the expression time course.
• PKC activators blocked the subcellular redistribution induced by SERT substrates.

Conclusions:

• Endogenous SERT expression in developing thalamocortical neurons is differentially regulated by serotonin (5-HT) and psychostimulants.
• SERT modulation involves changes in both total protein levels and transporter subcellular redistribution.
• Psychostimulant-induced alterations in SERT expression may contribute to their effects on neocortical development and 5-HT signaling.