Serotonin (5-HT) 5-HT_2A Receptor (5-HT_2AR):5-HT_2CR Imbalance in Medial Prefrontal Cortex Associates with Motor Impulsivity

Abstract

A feature of multiple neuropsychiatric disorders is motor impulsivity. Recent studies have implicated serotonin (5-HT) systems in medial prefrontal cortex (mPFC) in mediating individual differences in motor impulsivity, notably the 5-HT2AR receptor (5-HT2AR) and 5-HT2CR. We investigated the hypothesis that differences in the ratio of 5-HT2AR:5-HT2CR protein expression in mPFC would predict the individual level of motor impulsivity and that the engineered loss of the 5-HT2CR would result in high motor impulsivity concomitant with elevated 5-HT2AR expression and pharmacological sensitivity to the selective 5-HT2AR antagonist M100907. High and low impulsive rats were identified in a 1-choice serial reaction time task. Native protein levels of the 5-HT2AR and the 5-HT2CR predicted the intensity of motor impulsivity and the 5-HT2AR:5-HT2CR ratio in mPFC positively correlated with levels of premature responses in individual outbred rats. The possibility that the 5-HT2AR and 5-HT2CR act in concert to control motor impulsivity is supported by the observation that high phenotypic motor impulsivity associated with a diminished mPFC synaptosomal 5-HT2AR:5-HT2CR protein:protein interaction. Knockdown of mPFC 5-HT2CR resulted in increased motor impulsivity and triggered a functional disruption of the local 5-HT2AR:5-HT2CR balance as evidenced by a compensatory upregulation of 5-HT2AR protein expression and a leftward shift in the potency of M100907 to suppress impulsive behavior. We infer that there is an interactive relationship between the mPFC 5-HT2AR and 5-HT2CR, and that a 5-HT2AR:5-HT2CR imbalance may be a functionally-relevant mechanism underlying motor impulsivity.

Incubation of cocaine cue reactivity associates with neuroadaptations in the cortical serotonin (5-HT) 5-HT2C receptor (5-HT2CR) system

“…Proteins were transferred to a PVDF membrane (BioRad, Hercules, CA) via a wet-transfer electroblotting apparatus (BioRad) overnight at 60–70V (Anastasio et al, 2010). Membranes were blocked with Odyssey blocking buffer [LI-COR® Biosciences; 1:1 in Tris Buffered Saline (TBS), pH 7.4] followed by incubation with primary antibody [mouse monoclonal 5-HT 2C R (D-12, sc-17797, Santa Cruz; 1:100), mouse monoclonal pan-cadherin (ab6528, Abcam; 1:5000)] (Anastasio et al, 2010; Anastasio et al, 2015; Fink, 2015). Membranes were rinsed in TBS + 0.1% Tween-20 (TBS-T), incubated with secondary antibody [infrared-labeled goat anti-mouse IRDye ™ 800CW (926-32210) or IRDye ™ 680RD (926-68070; LI-COR® Biosciences, Lincoln, NE, 1:10000)], then rinsed in TBS-T. PVDF membranes were imaged using the Odyssey® Infrared Imaging System (LI-COR® Biosciences, Lincoln, NE).…”

“…The subcellular localization (synaptosomal; membrane vs. cytoplasmic) profile of the mPFC 5-HT 2C R protein was assessed via the Wes ™ automated Western blotting system (ProteinSimple, San Jose, CA) which utilizes capillary electrophoresis-based immunodetection for higher resolution, sensitivity, and reproducibility (even at low sample concentrations) relative to traditional immunoblotting techniques (Anastasio et al, 2015; Fink, 2015; Liu et al, 2013). Wes ™ reagents (biotinylated molecular weight marker, streptavidin-HRP fluorescent standards, luminol-S, hydrogen peroxide, sample buffer, DTT, stacking matrix, separation matrix, running buffer, wash buffer, and matrix removal buffer, secondary antibodies, antibody diluent, and capillaries) were obtained from the manufacturer (ProteinSimple) and used according to the manufacturer’s recommendations with minor modifications (Anastasio et al, 2015; Fink, 2015).…”

“…Wes ™ reagents (biotinylated molecular weight marker, streptavidin-HRP fluorescent standards, luminol-S, hydrogen peroxide, sample buffer, DTT, stacking matrix, separation matrix, running buffer, wash buffer, and matrix removal buffer, secondary antibodies, antibody diluent, and capillaries) were obtained from the manufacturer (ProteinSimple) and used according to the manufacturer’s recommendations with minor modifications (Anastasio et al, 2015; Fink, 2015). The mouse monoclonal 5-HT 2C R (D-12, sc-17797, Santa Cruz; 1:50), mouse monoclonal pan-cadherin (ab6528, Abcam; 1:10000), and mouse monoclonal GAPDH antibody (6C5, Advanced Immunochemicals; 1:50000) were diluted with ProteinSimple antibody diluent.…”

Alterations in cortical thickness in nonmedicated premature ejaculation patients: A morphometric MRI study

“…On the other hand, a complex interplay of neurotransmitters, play important roles in ejaculation 5‐hydroxytryptamine (5‐HT) is the most pertinent with regard to PE . The changes of 5‐HT systems in prefrontal cortex, proved as the mediator of individual differences in motor impulsivity, may also be contributor to the alteration of cortical thickness …”

“…37 The changes of 5-HT systems in prefrontal cortex, proved as the mediator of individual differences in motor impulsivity, may also be contributor to the alteration of cortical thickness. 39 This study has several limitations. First, whether such cortical changes are the cause or the consequence of PE is still not clear.…”