Dopamine reward circuitry: Two projection systems from the ventral midbrain to the nucleus accumbens–olfactory tubercle complex

Abstract

Anatomical and functional refinements of the meso-limbic dopamine system of the rat are discussed. Present experiments suggest that dopaminergic neurons localized in the posteromedial ventral tegmental area (VTA) and central linear nucleus raphe selectively project to the ventromedial striatum (medial olfactory tubercle and medial nucleus accumbens shell), whereas the anteromedial VTA has few if any projections to the ventral striatum, and the lateral VTA largely projects to the ventrolateral striatum (accumbens core, lateral shell and lateral tubercle). These findings complement the recent behavioral findings that cocaine and amphetamine are more rewarding when administered into the ventromedial striatum than into the ventrolateral striatum. Drugs such as nicotine and opiates are more rewarding when administered into the posterior VTA or the central linear nucleus than into the anterior VTA. A review of the literature suggests that (1) the midbrain has corresponding zones for the accumbens core and medial shell; (2) the striatal portion of the olfactory tubercle is a ventral extension of the nucleus accumbens shell; and (3) a model of two dopamine projection systems from the ventral midbrain to the ventral striatum is useful for understanding reward function. The medial projection system is important in the regulation of arousal characterized by affect and drive and plays a different role in goal-directed learning than the lateral projection system, as described in the variation-selection hypothesis of striatal functional organization.

Escalation in high fat intake in a binge eating model differentially engages dopamine neurons of the ventral tegmental area and requires ghrelin signaling

“…In response to the successive exposures to a rewarding stimulus, the role of the VTA dopamine system is rather sophisticated: the Acb dopamine signaling increases after the first exposure and then habituates with the repeated exposures and becomes a predictive signal of the stimulus (Salamone and Correa, 2012;Schultz, 2010). On top of this functional complexity, the VTA dopamine neurons are located in diverse sub-regions within this nucleus that, in turn, are part of different neuronal circuits for which their independent physiological role is virtually unknown (Ferreira et al, 2008;Ikemoto, 2007Lammel et al, 2011. Here, we found that IF and PBP dopamine neurons are activated in mice exposed to either one or four HFD consumption events; however, the level of activation was higher in mice exposed to four HFD consumption events.…”

“…Quantitative analysis was performed in sections between bregma 0.86 and 1.18 mm for the Acb, between bregma −1.22 and −1.94 mm for the lateral hypothalamic area (LHA), and between bregma −3.28 and −3.92 mm for the VTA. For the analysis, the Acb was subdivided into medial Acb shell (MAcbSh), lateral Acb shell (LAcbSh) and Acb core (AcbC) while the VTA was subdivided into paranigral (PN), parabrachial pigmented (PBP) and interfascicular (IF) subnuclei, according to previous descriptions (Ikemoto, 2007;Kelley, 2004). Anatomical limits of each brain region were identified using a mouse brain atlas (Paxinos and Franklin, 2001).…”

microRNA and mRNA profiles in nucleus accumbens underlying depression versus resilience in response to chronic stress

“…The nucleus accumbens is considered as an important region of brain reward circuits (Basar et al, 2010; Carlezon & Thomas, 2009; Day & Carelli, 2007; Floresco, 2015; Ikemoto, 2007; Salamone, Correa, Mingote, & Weber, 2005). Spiny GABAergic neurons in the nucleus accumbens are involved in major depression (Francis & Lobo, 2016; Lim, Huang, Grueter, Rothwell, & Malenka, 2012; Wang et al, 2010).…”

Divergent anomaly in mesocorticolimbic dopaminergic circuits might be associated with different depressive behaviors, an animal study

“…The mesocorticolimbic dopaminergic system, composed of dopaminergic neurons and their projections, has been proven to be involved in the reward‐motivated behaviors of individuals (Cohen, Haesler, Vong, Lowell, & Uchida, 2012; Ikemoto, 2007). The dopaminergic neurons are mainly located in the ventral tegmental area (VTA) (Beckstead, Domesick, & Nauta,1979) and project primarily to the prefrontal cortex (PFC), olfactory tubercle (OT), nucleus accumbens (NAc), dorsal striatum (ST), and the amygdala (AMy).…”