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Free keywords:
mouse, odorant, olfaction, social buffering, stress
Abstract:
Within the main olfactory system of mammals, a unique subsystem exists
that is comprised of sensory neurons expressing odorant receptors (ORs)
of the OR37 subfamily. These receptors are exclusive for mammals and are
highly conserved across species. The mouse OR37 receptor subtypes A, B
and C were shown to be activated by the long-chain aliphatic aldehydes
pentadecanal, hexadecanal and heptadecanal, respectively. The search for
biological sources of these compounds showed that bodily secretions from
conspecifics activated the OR37A, B and C glomerulus. At the same time,
the activity of cells in a target region of projection neurons from OR37
glomeruli, the paraventricular nucleus of the hypothalamus (PVN), was
reduced compared with controls (clean test box). A large number of the
activated cells in the PVN of mice that were placed into a clean test
box were corticotropin-releasing hormone cells, indicating an induction
of the stress axis due to the novel environment. The much lower number
of activated cells of mice in a box enriched with bodily secretions from
conspecifics indicated a reduced stress response. As bodily secretions
from conspecifics activated the OR37 system and simultaneously reduced
stress-induced activation of the PVN, it was tested whether the ligands
for OR37 receptors could induce this effect. Indeed, a similarly reduced
activity in the PVN was found in mice kept in a clean test box and
exposed to a mixture of the OR37 ligands delivered via an air stream.
These data indicate that the OR37 system may play a role in mediating a
phenomenon called social buffering.
