AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 3 744-R751, Copyright © 1995 by American Physiological Society
Catecholaminergic innervation of white adipose tissue in Siberian hamsters
T. G. Youngstrom and T. J. Bartness
Department of Psychology, Georgia State University, Atlanta 30303.
When Siberian hamsters are transferred from long summerlike days (LDs) to
short winterlike days (SDs) they decrease their body weight, primarily as
body fat. These SD-induced decreases in lipid stores are not uniform.
Internally located white adipose tissue (WAT) pads are depleted
preferentially of lipid, whereas the more externally located subcutaneous
WAT pads are relatively spared. These data suggest a possible differential
sympathetic neural control over catecholamine-induced lipolysis and that
lipolytic rates are greater for internal vs. external WAT pads. Moreover,
if these differential rates of lipolysis are due to differential
sympathetic nervous system (SNS) drives on the pads, then fat pad-specific
catecholaminergic innervation may exist. Therefore, we tested whether
inguinal WAT (IWAT; an external pad) and epididymal WAT (EWAT; an internal
pad) were innervated differentially. In addition, we tested whether
norepinephrine (NE) turnover (TO) reflected the presumed greater SNS drive
on EWAT vs. IWAT after SD exposure. Injections of fluorescent tract tracers
[Fluoro-Gold or indocarbocyanine perchlorate (DiI)] demonstrated
projections from the SNS ganglia T13-L3 to both fat pads. Retrograde
labeling revealed a relatively separate pattern of distribution of labeled
neurons in the ganglia projecting to each pad. In vivo anterograde
transport of DiI resulted in labeling in both IWAT and EWAT that included
staining around individual adipocytes and occasionally retrogradely labeled
cells. The proportionately greater decrease in EWAT compared with IWAT mass
after 5 wk of SD exposure was reflected in greater EWAT NE TO than found in
their LD counterparts for this pad.(ABSTRACT TRUNCATED AT 250 WORDS)
