Identification of brain neurons expressing the dopamine D4 receptor gene using BAC transgenic mice

Abstract

The dopamine D4 receptor (D4R) has received considerable interest because of its higher affinity for atypical antipsychotics, the extremely polymorphic nature of the human gene and the genetic association with attention deficit and hyperactivity disorder (ADHD). Several efforts have been undertaken to determine the D4R expression pattern in the brain using immunohistochemistry, binding autoradiography and in situ hybridization, but the overall published results present large discrepancies. Here, we have explored an alternative genetic approach by studying bacterial artificial chromosome (BAC) transgenic mice that express enhanced green fluorescent protein (EGFP) under the transcriptional control of the mouse dopamine D4 receptor gene (Drd4). Immunohistochemical analysis performed in brain sections of Drd4-EGFP transgenic mice using an anti-EGFP polyclonal antibody showed that transgenic expression was predominant in deep layer neurons of the prefrontal cortex, particularly in the orbital, prelimbic, cingulate and rostral agranular portions. In addition, discrete groups of Drd4-EGFP labelled neurons were observed in the anterior olfactory nucleus, ventral pallidum, and lateral parabrachial nucleus. EGFP was not detected in the striatum, hippocampus or midbrain as described using other techniques. Given the fine specificity of EGFP expression in BAC transgenic mice and the high sensitivity of the EGFP antibody used in this study, our results indicate that Drd4 expression in the adult mouse brain is limited to a more restricted number of areas than previously reported. Its leading expression in the prefrontal cortex supports the importance of the D4R in complex behaviours depending on cortical dopamine (DA) transmission and its possible role in the etiopathophysiology of ADHD.

Decreased Dopamine D4 Receptor Expression Increases Extracellular Glutamate and Alters Its Regulation in Mouse Striatum

“…The NAc has projections from similar areas, such as infralimbic and cingulate areas, but there is an increasing amount of projections from the hippocampus, entorhinal cortex, piriform cortex, amygdala, and subiculum (McGeorge and Faull, 1989). There is indication that these areas projecting to the NAc may have lower amounts of DRD4 influence (as compared with striatal projections) and, therefore, may not be as affected by loss of the DRD4, which may explain why we see data trends (Noain et al, 2006). Also, Rivera et al (2002) reported higher local expression of DRD4 in the Str in comparison with the NAc of rats, but the presence of DRD4 in these areas is debated (Noain et al, 2006).…”

“…There is indication that these areas projecting to the NAc may have lower amounts of DRD4 influence (as compared with striatal projections) and, therefore, may not be as affected by loss of the DRD4, which may explain why we see data trends (Noain et al, 2006). Also, Rivera et al (2002) reported higher local expression of DRD4 in the Str in comparison with the NAc of rats, but the presence of DRD4 in these areas is debated (Noain et al, 2006). Our recordings were made in the NAc core.…”

“…The organization of the corticostriatal projections are such that glutamatergic pyramidal neurons that have cell bodies mostly in lamina 5 (with some in 3 and 6) of the frontal cortex project to the Str and NAc (McGeorge and Faull, 1989). The DRD4 have a cellular distribution to these pyramidal neurons in lamina 5 (and some in 3) (Noain et al, 2006;Mrzljak et al, 1996;Ariano et al, 1997b); although Berger et al (2001) reported DRD4 localization mainly to layers 2-4 with only small amounts in 5. Our Glu and KCl data were taken from the dorsomedial Str, which has projections from the visual, cingulate, agranular insular cortex, motor 2 regions, and auditory parts of the cerebral cortex (McGeorge and Faull, 1989).…”

Etiology of Food Addiction

“…D4 reseptörleri temel olarak ventral tegmental alan, prefrontal korteks, singulat girus ve insuladan gelen mezokortikal projeksiyonların uyardığı bölgelerde yerleşmiş-tir. [59] DRD-4 7R aleli olan bulimiası olan kadınlarda yaşam boyu artmış beden kitle indeksi riskinin olduğu gösterilmiştir. [60] Bir başka preklinik araştırmada fareler ile yapılan bir deneyde, DAT geninde olan bir bozulmanın sinaptik dopamin artışına ve artmış enerji alımı ile lezzetli yiyeceklerin tüketiminde artışla sonuçlandığı saptanmıştır.…”

Neuregulin links dopaminergic and glutamatergic neurotransmission to control hippocampal synaptic plasticity

“…It is important to note, however, that D4R mRNA and protein levels are exceedingly low in the hippocampus, and its expression in pyramidal cells and/or interneurons is far from established. [16][17][18] The known spatial distribution of some crucial elements might be helpful, however, in assembling a network model: First, ErbB4 is expressed in numerous GABAergic interneurons across all layers (see below). Second, glutamatergic SC→CA1 synapses are located in the stratum radiatum.…”