Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.09.373845v1?rss=1 Authors: Suyama, H., Egger, V., Lukas, M. Abstract: Social discrimination in rats requires activation of the intrinsic bulbar vasopressin system, but it is unclear how this system comes into operation. Here we show that a higher number of bulbar vasopressin cells (VPC) is activated by stimulation with a conspecific compared to rat urine, indicating that VPC activation depends on more than olfactory cues during social interaction. In-vitro slice electrophysiology combined with pharmacology and immunohistochemistry then demonstrated that centrifugal cholinergic inputs from the diagonal band of Broca can enable olfactory nerve-evoked action potentials in VPCs via muscarinic neuromodulation. Finally, such muscarinic activation of the vasopressin system is essential for vasopressin-dependent social discrimination, since recognition of a known rat could be blocked by a muscarinic antagonist and rescued by additional application of vasopressin. For the first time, we demonstrated that top-down cholinergic modulation of bulbar VPC activity in a social context is crucial for individual social discrimination in rats. Copy rights belong to original authors. Visit the link for more info