Distribution, connection and function of ALDH1A1/TH neurons in substantia nigra pars reticulata of mouse.

The massive cell death of dopaminergic neurons (DANs) in substantia nigra pars compacta (SNC) is associated with motor diseases, such as Parkinson's disease. Moreover, as a subtype of DANs in SNC, ALDH1A1 neurons show better resistance to PD related neurotoxin. DANs can also be found in the substantia nigra pars reticulata (SNR), however, whether they are ALDH1A1 neurons are rarely reported, as well as their projection, function, and reaction in the PD pathology. We studied the distribution of ALDH1A1 neurons and track their projection by injecting pAAV. We figured out that, in SNR, 87 % neurons are ALDH1A1/TH in ALDH1A1 cluster averagely, while ALDH1A1/TH: TH is 52 % averagely. There are two enrichment regions of ALDH1A1/TH neurons at brgma -3.40 mm and brgma -3.70 mm in the SNR of the nTg mice. Nevertheless, in one type of PD-liked mice model, the proportion of ALDH1A1/TH: ALDH1A1 neurons are 98 % averagely, while ALHD1A1/TH: TH is 57 %. Intriguingly, neuro-tracing discovered that there may be a previously unreported connection between SNR and anterior dorsal thalamus (ADT). The mouse received MPTP stereotactic injection to destroy TH neurons in SNR showed depression behavior, indicated the DANs death in SNR may contribute to depression behavior.