Research articlel-Carnosine's dose-dependent effects on muscle sympathetic nerves and blood flow

- l-Carnosine has dose-dependent effects on muscle sympathetic nerve activity.
- l-Carnosine has dose-dependent effects on muscle blood flow.
- The increase in muscle blood flow was realized via β-adrenergic receptor.

l-Carnosine is synthesized in mammalian muscles and brain and affects autonomic neurotransmission and physiological phenomena. To clarify the role of l-carnosine, the effects of intraduodenal administration of l-carnosine on muscle sympathetic nerve activity (muscle-SNA) and blood flow (BF) were examined. The changes in muscle-SNA and BF were examined using electrophysiological and Doppler flowmeter in urethane-anesthetized rats. The effect of propranolol, a β-adrenergic antagonist, on the increase in muscle BF due to l-carnosine was also examined. Low dose (1 μg/300 g body weight [bw]) of l-carnosine increased both muscle-SNA and muscle BF, while high dese (100 mg/300 g bw) of l-carnosine decreased both muscle-SNA and muscle BF. Furthermore, propranolol eliminated the increase in muscle BF caused by a low dose of l-carnosine. These results suggest that l-carnosine has dose-dependent effects on muscle BF via changes in muscle-SNA, and the β-adrenergic receptor is implicated in the increase in muscle BF due to l-carnosine.