Despite that they represent only 2% of the total MSNs population of the adult mice dorsal striatum, the D1/D2 MSNs might play an important role in striatal functioning, as it is the case of striatal interneurons, which account only for 2–3% of striatal neurons in rodents4344. Their presence throughout the dorsal striatum suggest that the D1/D2 MSNs are involved in the sensorimotor and associative functions of the striatum, which are integrated mainly within the caudolateral and the rostromedial sector of the structure, respectively45. However, the prevalence of the D1/D2 MSNs in the Acb indicates that these neurons are even more actively implied in the limbic aspect of striatal functioning. Indeed, we found the density of D1/D2 MSNs in the Acb to be significantly higher than in the dorsal striatum, a finding that is congruent with data from previous studies conducted in transgenic mice2021244647 and by a higher number of D1/D2 heteromer in the rat and monkey Acb2526. The shell compartment of the Acb was significantly more enriched in D1/D2 MSNs than the core compartment, supporting the notion that the latter
