Neurochemical evidence supporting dopamine D1–D2 receptor heteromers in the striatum of the long-tailed macaque: changes following dopaminergic manipulation

Abstract

Although it has long been widely accepted that dopamine receptor types D1 and D2 form GPCR heteromers in the striatum, the presence of D1–D2 receptor heteromers has been recently challenged. In an attempt to properly characterize D1–D2 receptor heteromers, here we have used the in situ proximity ligation assay (PLA) in striatal sections comprising the caudate nucleus, the putamen and the core and shell territories of the nucleus accumbens. Experiments were carried out in control macaques as well as in MPTP-treated animals (with and without dyskinesia). Obtained data support the presence of D1–D2 receptor heteromers within all the striatal subdivisions, with the highest abundance in the accumbens shell. Dopamine depletion by MPTP resulted in an increase of D1–D2 density in caudate and putamen which was normalized by levodopa treatment. Two different sizes of heteromers were consistently found, thus suggesting that besides individual heteromers, D1–D2 receptor heteromers are sometimes organized in macromolecular complexes made of a number of D1–D2 heteromers. Furthermore, the PLA technique was combined with different neuronal markers to properly characterize the identities of striatal neurons expressing D1–D2 heteromers. We have found that striatal projection neurons giving rise to either the direct or the indirect basal ganglia pathways expressed D1–D2 heteromers. Interestingly, macromolecular complexes of D1–D2 heteromers were only found within cholinergic interneurons. In summary, here we provide overwhelming proof that D1 and D2 receptors form heteromeric complexes in the macaque striatum, thus representing a very appealing target for a number of brain diseases involving dopamine dysfunction.

Striatal Dopamine D2-Muscarinic Acetylcholine M1 Receptor–Receptor Interaction in a Model of Movement Disorders

“…Here, we describe a novel interaction between the D 2 R and M 1 R in the striatum, which may eventually harmonize with those previously described for D 2 R (Cabello et al, 2009;Lukasiewicz et al, 2010;Borroto-Escuela et al, 2013;Bonaventura et al, 2014;Fernandez-Duenas et al, 2015;Rico et al, 2017;Vasudevan et al, 2019). In addition, we evaluated the antiparkinsonian efficacy of a combined D 2 R agonist (i.e., sumanirole) and M 1 R antagonist (i.e., VU0255035) treatment using the reserpine animal model of experimental parkinsonism.…”

Botulinum Neurotoxin A Injected Ipsilaterally or Contralaterally into the Striatum in the Rat 6-OHDA Model of Unilateral Parkinson’s Disease Differently Affects Behavior

“…The majority of inhibitory D2 receptors are located on cholinergic interneurons and medium spiny neurons (MSN) projecting to the external pallidum, i.e., being part of the indirect basal ganglia loop (Hurley and Jenner, 2006; Perreault et al, 2011; Bordia et al, 2016; Mamaligas et al, 2016; Rico et al, 2017). As in hemi-PD the tonically active cholinergic interneurons become hyperactive due to loss of D2-mediated DA inhibition, they strongly activate MSN by ACh.…”

FFAR2‐FFAR3 receptor heteromerization modulates short‐chain fatty acid sensing

“…Because all 3 cell types stained positive for FFAR2 and FFAR3 in our previous study via IHC (29), this suggests that the coexpression of FFAR2 and FFAR3 alone, as was observed in colon epithelial cells, does not necessarily lead to FFAR2-FFAR3 heteromer formation. Cell-specific heteromerization has been observed for other GPCRs such as the D 1 -D 2 dopamine heteromer (43). The cell-specific PLA staining is also consistent with a specific PLA signal that was only generated upon heteromer formation.…”