Effects of olfactory stimulation with scents of grapefruit and lavender essential oils on the skeletal muscle sympathetic nerve and muscle blood flow in rats

We have previously observed that olfactory stimulation with scents of grapefruit and lavender oils have opposing effects on autonomic neurotransmission and physiological phenomena in rats. Since the suppression and facilitation of activity of the sympathetic nerves innervating the skeletal muscles decreases and increases the skeletal muscle blood flow (skeletal muscle-BF), respectively, the effects of olfactory stimulation with scent of a grapefruit essential oil (SGFO) and scent of a lavender essential oil (SLVO) on skeletal muscle sympathetic nerve activity (skeletal muscle-SNA) and skeletal muscle-BF were examined. SGFO reduced, and SLVO elevated skeletal muscle-SNA and skeletal muscle-BF, respectively. Furthermore, 1) anosmic treatment with ZnSO4 eliminated the changes in skeletal muscle-SNA due to SGFO and SLVO, 2) diphenhydramine, a histamine H1-antagonist, eliminated the SGFO-induced suppression of skeletal muscle-SNA, and thioperamide, a histamine H3-antagonist, abolished the SLVO-induced enhancement of skeletal muscle-SNA, and 3) butoxamine, an adrenergic β2-antagonist, blocked the SLVO-induced increase in skeletal muscle-BF. These findings suggest that olfactory stimulation with SGFO reduces, and SLVO enhances, skeletal muscle-BF via these autonomic changes. In addition, the histamine H1-receptor was found to be involved in the SGFO-induced suppression of skeletal muscle-SNA, the H3-receptor was shown to be concerned to the SLVO-induced enhancement of skeletal muscle-SNA, and the adrenergic β2-receptor was indicated to be implicated in the SLVO-induced increase in skeletal muscle-BF via an increase in skeletal muscle-SNA. These findings suggest that SGFO may suppress, and SLVO may enhance, the muscle recovery from muscle fatigue and the growth of muscles, via changes in autonomic neurotransmission.