Effects of central injection of l-carnosine on sympathetic nerve activity innervating brown adipose tissue and body temperature in rats

In the present study, using urethane-anesthetized rats, we examined the effects of intralateral cerebral ventricular (LCV) injection of various doses of l-carnosine on neural activity innervating brown adipose tissue (BAT-SNA) and body temperature (BT). We found that injection of a low dose of l-carnosine (0.01 μg) suppressed BAT-SNA significantly. Conversely, a high dose (100 μg) of l-carnosine significantly elevated BAT-SNA. In the light period (14:00), brown adipose tissue temperature (BAT-T) and BT were suppressed after low and elevated after high dose injection of l-carnosine whereas in the dark period (2:00), these parameters remained unchanged with l-carnosine treatment. Bilateral lesions of the hypothalamic suprachiasmatic nucleus (SCN) abolished the effects of low and high doses of l-carnosine on BAT-SNA, BAT-T and BT. Furthermore, high dose treatment with l-carnosine altered c-Fos induction in the SCN and the PVN. These results suggest that l-carnosine affects BAT-SNA, BAT-T and BT in a dose-dependent manner in the rat, and that the SCN may be involved in these effects.