WHITE ADIPOSE-TISSUE SYMPATHETIC NERVOUS-SYSTEM DENERVATION INCREASESFAT PAD MASS AND FAT-CELL NUMBER

The sympathetic nervous system (SNS) drive on white adipose tissue (WA T) was varied to test its effects on fat cell number (FCN) under condi tions in which lipolysis would be minimized and therefore partially se parable from SNS trophic effects. The inguinal subcutaneous WAT (IWAT) pad of Siberian hamsters was chosen because 1) it is innervated by th e SNS, 2) short day (SD) exposure increases its SNS drive (similar to 250%) without proportionately increasing lipolysis, and 3) surgical de nervation eliminates its SNS innervation. IWAT was either unilaterally surgically or sham denervated, while the contralateral pad was left. intact. In long day- or SD-exposed hamsters (11 wk), IWAT denervation decreased norepinephrine content (similar to 80%) and increased fat pa d mass (similar to 200%) and FCN (similar to 250 and similar to 180%, respectively) compared with the contralateral intact pads, but did not affect fat cell size (FCS). The denervation-induced increased FCN in SDs occurred despite naturally occurring decreased food intake. SDs de creased IWAT FCS regardless of the surgical treatment. These results s upport an important role of WAT SNS innervation in the control of FCN in vivo.