Wj. Drijfhout et al., MICRODIALYSIS REVEALS DYNAMICS OF COUPLING BETWEEN NORADRENALINE RELEASE AND MELATONIN SECRETION IN CONSCIOUS RATS, Neuroscience letters, 202(3), 1996, pp. 185-188
The coupling between noradrenergic innervation of the pineal gland and
melatonin production was investigated. Previously, the development of
a microdialysis; technique was described which made it possible to st
udy the noradrenaline (NA) input as well as the melatonin output with
high time resolution. In the present study, we studied the effects of
short-term changes in NA-release on melatonin secretion. A 1 min light
pulse was applied around midnight and resulted in an immediate decrea
se of both NA and melatonin. While NA returned to basal levels in 40 m
in, melatonin did not reach the baseline within 2.5 h. This discrepanc
y in correlation between NA and melatonin indicates a rapid inactivati
on of N-acetyl-transferase (NAT), followed by a slow reactivation, pos
sibly by de novo synthesis of NAT. During daytime, a perfusion with 60
mM potassium for 30 min, resulted in a rapid and short stimulation of
NA release, which was not followed by an increase in melatonin produc
tion. This indicates that 30 min stimulation of NAT activation is not
enough to increase the amount of melatonin produced. The combination o
f measuring NA input and melatonin output appears to be a valuable too
l in studying the characteristics of pineal activity in great detail.