In vivo and real-time monitoring of gene
expression in the deep structure of the brain could bring beneficial information for understanding neuroendocrine and
autonomic nervous system. We developed a system which could monitor green
fluorescent protein (GFP)-expression in the rat brain via optical fiber. One terminal of optical fiber was connected to blue semiconductor laser oscillators/ green fluorescent detector. The other terminal was inserted
into the brain and fixed with the cranium. Because the optical
fiber is vulnerable to twist caused by animal
free moving, we also developed a cage which turns the floor in
response to turning of rat’s head for relief of twist-stress of optical fiber
between laser oscillator / fluorescent detector and the rat’s head. This
system enables real-time monitoring of GFP-expression with awake and
unrestrained rat for a week or more. We applied this system to the
arginine vasopressin (AVP)-eGFP transgenic rats in which GFP was expressed in
the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) in the
hypothalamus. These transgenic rats have been reported an increase of GFP-expression
in the PVN and the SON under salt-loading condition (Ueta et al. Endocrinology, 2005). Using our real-time monitoring
system, we detected an increase of AVP-expression in the hypothalamus via GFP-expression under dehydration. After
monitoring via optical fiber, the brain were fixed and cut into slices
for observation of the position of fiber-insertion. We also found fluctuation
of fluorescent intensity with several hours period. It was considered to be reflected
by AVP-expression with the same period. In this study, we show a new monitoring
tool of gene expression in the deep structure of brain.