Autonomic and cardiovascular responses to scent stimulation are altered in cry KO mice

Previously, we observed that in rats, olfactory stimulation with scent of grapefruit oil (SGFO) elevates the activities of sympathetic nerves. SGFO also suppresses gastric vagal (parasympathetic) nerve activity (GVNA), increases the plasma glycerol concentration, blood pressure (BP) and body temperature, and reduces appetite. In contrast, olfactory stimulation with scent of lavender oil (SLVO) has opposite effects in rats. Here, we show that in mice, olfactory stimulation with SGFO elevated activities of sympathetic nerves innervating the kidney, adrenal gland and brown adipose tissue as well as increasing BP and suppressing GVNA, whereas olfactory stimulation with SLVO decreased these sympathetic nerve activities and BP, and elevated GVNA. Electrolytic lesions of the mouse hypothalamic suprachiasmatic nucleus (SCN) eliminated changes in renal sympathetic nerve activity (RSNA), BP and GVNA induced by either SGFO or SLVO. Furthermore, SGFO-induced elevations in RSNA and BP and the SLVO-induced GVNA increase were not observed in Cryptochrome (Cry)-deficient mice, which harbor mutations in both cry1 and cry2 and lack normal circadian rhythms. These findings suggest that SGFO and SLVO affect autonomic neurotransmission and BP via the SCN in mice. Moreover, the molecular clock mechanism in the SCN, which involves the cry1 and cry2 genes, is partially involved in mediating these autonomic and cardiovascular actions of SGFO and SLVO.