Neuroanatomical Relationship Between Nucleus Accumbens A2AR Neurons and Orexin Neurons in the Mouse Brain.

To explore morphological evidence for neuronal circuits between adenosine A2A receptor (A2AR) neurons in the nucleus accumbens (NAc) and orexin neurons. The utilized adeno-associated virus (AAV) encoding humanized Renilla green fluorescent protein (hrGFP) as a tracer to visualize the expression of the A2AR neurons in the NAc and their axon distributions in orexin neurons. The Cre-dependent AAV was injected into the NAc in adenosine A2AR-Cre mice. Immunohistochemistry was then used to visualize hrGFP and their projections in orexin neurons. The data revealed that NAc A2AR neurons, mainly expressed in g-aminobutyric acidergic (GABAergic) projection neurons, projected to the hypothalamus, with apparent contacts of hrGFP containing boutons onto orexin-immunoreactive (IR) soma and dendrites. We also observed strong staining of orexin-IR varicose terminals in the NAc, with apparent contacts of orexin-IR terminals onto A2AR neurons. Furthermore, in the NAc, orexin-IR varicosities contained vesicular glutamate transporter 2 (VGluT2) and synaptophysin (Syp). These data provide morphological evidence for exploring the function between NAc A2AR neurons and orexin neuron in the hypothalamus, particularly in regulating sleep processes. [ABSTRACT FROM AUTHOR]