Repeated Clozapine Increases the Level of Serotonin 5-HT1AR Heterodimerization with 5-HT2A or Dopamine D2 Receptors in the Mouse Cortex.

Marta Szlachta,Dariusz Żurawek,Agata Faron-Górecka,Marta Dziedzicka-Wasylewska,Magdalena Kolasa,Paulina Pabian,Maciej Kuśmider,Joanna Solich

doi:10.3389/fnmol.2018.00040

Marta Szlachta, Dariusz Żurawek + Show 6 more

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https://doi.org/10.3389/fnmol.2018.00040

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Abstract

G-protein–coupled receptor (GPCR) heterodimers are new targets for the treatment of schizophrenia. Dopamine D2 receptors and serotonin 5-HT1A and 5-HT2A receptors play an important role in neurotransmission and have been implicated in many human psychiatric disorders, including schizophrenia. Therefore, in this study, we investigated whether antipsychotic drugs (clozapine (CLZ) and haloperidol (HAL)) affected the formation of heterodimers of D2–5-HT1A receptors as well as 5-HT1A–5-HT2A receptors. Proximity ligation assay (PLA) was used to accurately visualize, for the first time, GPCR heterodimers both at in vitro and ex vivo levels. In line with our previous behavioral studies, we used ketamine to induce cognitive deficits in mice. Our study confirmed the co-localization of D2/5-HT1A and 5-HT1A/5-HT2A receptors in the mouse cortex. Low-dose CLZ (0.3 mg/kg) administered repeatedly, but not CLZ at 1 mg/kg, increased the level of D2–5-HT1A and 5-HT1A–5-HT2A heterodimers in the mouse prefrontal and frontal cortex. On the other hand, HAL decreased the level of GPCR heterodimers. Ketamine affected the formation of 5-HT1A–5-HT2A, but not D2–5-HT1A, heterodimers.

Highlights

It is well established that dopamine D2 receptors and serotonin 5-HT1A and 5-HT2A receptors play an important role in neurotransmission and that alterations in their functioning are implicated in many human neurological and psychiatric disorders, including schizophrenia
Radioligand binding determination to dopamine D2 as well as serotonin receptors (5HT1A and 5HT2A) using autoradiography was done before proximity ligation assay (PLA) experiments to exclude possibility that changes in receptors dimerization level resulted from drug influence on receptors density
Analysis of [3H]domperidone binding to dopamine D2 receptors in prefrontal cortex and frontal cortex in mouse brain did not show any significant differences after acute treatment of CLZ in dose 0.3 mg/kg (Figure 1B)

Summary

Introduction

It is well established that dopamine D2 receptors and serotonin 5-HT1A and 5-HT2A receptors play an important role in neurotransmission and that alterations in their functioning are implicated in many human neurological and psychiatric disorders, including schizophrenia. Clozapine (CLZ), an antipsychotic drug currently used in the clinic but still being the object of basic studies designed to search for its unique molecular features, has been shown to act via various heterodimers These studies have used in vitro systems (cell lines transfected with recombinant receptors) and sophisticated technology based on fluorescence resonance energy transfer. The affinity of D1 and 5-HT2A receptors for CLZ depends on whether they are present in the plasma membrane separately or together with the D2 receptor (FaronGórecka et al, 2008; Łukasiewicz et al, 2011) In another in vitro study, the D2 receptor was able to form constitutive heterodimers with another serotonin receptor, 5-HT1A, and CLZ significantly increased this interaction (Łukasiewicz et al, 2016). PLA was used to accurately visualize the heterodimers both in vitro and in ex vivo mouse brain

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