Brain research
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Based on the importance of paraventricular thalamic nucleus (PVT) as a relay station of energy balance, arousal, and food reward, we aimed in the present study to determine projection patterns of neuropeptide Y (NPY), cocaine- and amphetamine-regulated transcript (CART), melanin-concentrating hormone (MCH), and orexin (ORX)-ergic fibers to the PVT. First, the distribution of peptidergic axon terminals within the PVT was examined. NPY and CART terminals were confined within the boundary of the thalamic nucleus, exhibiting almost identical distribution. ⋯ Third, based on heavy projection from the PVT to the nucleus accumbens shell (NAcSh), the convergence of NPY and CART terminals on a single PVT neuron was identified; the proportion of labeled PVT neurons that received converging NPY/CART terminals compared with the total PVT neurons projecting to the NAcSh was 2.7% ± 0.6% (n = 3). Finally, PVT cells receiving NPY, CART, or ORX terminals provided divergent axon collaterals to NAcSh and medial prefrontal cortex. The present observations provided the anatomical evidence that the PVT might play an essential role in the integration of antagonistically-acting, feeding/arousal-related peptidergic inputs on their way to the cortical reward circuit.