Corticotropin releasing hormone-expressing inputs to the thalamic paraventricular nucleus: pathways from mother to memory?

Thalamic paraventricular nucleus (PVT) neurons expressing the corticotropin releasing hormone receptor 1 (CRHR1) are preferentially activated during early life stress. However, it is unclear how the receptor ligand, the stress-related peptide CRH, reaches receptor-bearing cells. To address this question, we mapped local, proximal and distal sources of CRH, i.e., CRH expressing neurons within, adjacent to and projecting to PVT. The combined use of retrograde and anterograde viral-genetic tracing approaches, validated with immunohistochemistry, identified an array of CRH neurons within PVT, in the adjacent paratenial nucleus as well as projecting to PVT from the parabrachial and Barrington nuclei. The latter are poised to convey to the PVT sensory signals from maternal grooming, as envisioned by Seymour Levine in the 1950s.