Lebouc, M. | bioRxiv Science

bioRxiv2026

tVTA controls dual dopaminergic inputs to the external Globus Pallidus

Midbrain dopamine (DA) neurons critically regulate basal ganglia function through their widespread projections. While the nigrostriatal pathway is well characterized and represents the dominant source of DA in the basal ganglia, other nuclei such as the external Globus Pallidus (GPe) also receive dopaminergic innervation, yet no consensus exists about its precise anatomical origin. In addition, the GABAergic tail of the ventral tegmental area (tVTA) provides a major inhibitory input to midbrain DA neurons, but its influence over DA pathways to the GPe remains unknown. In the rat, we combined retrograde tracing, immunohistochemistry, and ex vivo electrophysiology to identify distinct populations of DA neurons in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) that project to the GPe and display distinct electrophysiological properties. Using optogenetics and electrophysiology, we also demonstrate that these GPe-projecting DA neurons receive powerful inhibitory input from the tVTA. Together, our findings define both the origin and inhibitory control of dopaminergic innervation to the GPe, revealing a previously unrecognized disynaptic circuit (tVTA[->]DA[->]GPe) that refines our understanding of basal ganglia circuit function.

neuroscience↗

bioRxiv2024

Developmental alterations of indirect-pathway medium spiny neurons in mouse models of Huntington's disease.

Huntingtons disease (HD) is an inherited neurodegenerative disorder caused by a mutation in the gene encoding the Huntingtin protein (Htt). While symptoms, primarily characterized by progressive deterioration of the striatum and motor and cognitive functions, typically manifest in adulthood, recent studies have also highlighted developmental defects in HD. Indeed, alterations in cortical and striatal development have been observed in individuals carrying the mutation as early as in embryonic stages. However, despite the striatum being one of the most affected regions in HD, few studies have investigated potential developmental alterations in this structure, especially in the early weeks after birth. To address this question, we compared striatal development between wild-type (WT) mice and two murine models of HD, R6/1 and CAG140 mice crossed with reporter mice to identify D1- and D2-expressing medium spiny neurons (D1- and D2-MSNs). Using ex vivo electrophysiology and neuronal reconstruction, we observed that the maturation of electrical properties was selectively disrupted in D2-MSNs of the matrix compartment of HD mice during the first post-natal days. D2-MSNs arbor also an increased dendritic complexity. When studying the establishment of striatal afferents, we observed that cortico-striatal glutamatergic transmission was specifically reduced in D2-MSNs during the second postnatal week. All these alterations were transient before the circuit normalized on its own after the second postnatal week. These anatomical and electrophysiological data highlight the significant impact of the Htt mutation on numerous striatal development processes during the postnatal period. Interestingly, we observed that these alterations specifically affect MSNs in the indirect pathway. This preferential vulnerability aligns with the early death of these neurons in adulthood, suggesting that early treatment of these alterations could potentially modify the diseases progression.

neuroscience↗