Top-down acetylcholine contributes to social discrimination via enabling action potentials in olfactory bulb vasopressin cells

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.

Cholinergic transmission from the basal forebrain modulates social memory in male mice

“…Males seem to be more reliant on vasopressin, acting on its V1a receptor, for social recognition than females (Bredewold & Veenema, 2018; Gabor et al, 2012). Interestingly, ACh has been shown to stimulate vasopressin release in the hypothalamus, amygdala and olfactory bulb (Gregg, 1985; Hillhouse & Milton, 1989; Raber et al, 1994; Suyama et al, 2021). As we only investigated the role of cholinergic signalling in male mice, it is thus possible that the deficits in social recognition we observed result, at least in part, from decreased vasopressin release.…”