Vol. 276, Issue 4, R1078-R1086, April 1999
Interstrain differences in activity pattern, pineal function,
and SCN melatonin receptor density of rats
Gabriela
Klante1,
Karin
Secci2,
Mireille
Masson-Pévet3,
Paul
Pévet3,
Berthe
Vivien-Roels3,
Stephan
Steinlechner4, and
Franziska
Wollnik1
1 Biological Institute,
Department of Animal Physiology, University of Stuttgart, D-70550
Stuttgart; 2 Faculty of Biology,
University of Konstanz, D-78434 Konstanz;
4 Institute of Zoology, Hanover
School of Veterinary Medicine, D-30559 Hannover, Germany; and
3 Université Louis Pasteur,
F-67000 Strasbourg, France
We investigated the possibility that
strain-dependent differences in the diurnal pattern of wheel running
activity rhythms are also reflected in the melatonin profiles. The
inbred rat strains ACI/Ztm, BH/Ztm, and LEW/Ztm. LEW were
examined for diurnal [12:12-h light-dark (LD)] wheel
running activity, urinary 6-sulphatoxymelatonin (aMT6s) excretion,
melatonin concentrations of plasma and pineal glands, and melatonin
receptor density in the suprachiasmatic nuclei (SCN). ACI rats
displayed unimodal activity patterns with a high level of activity,
whereas BH and LEW rats showed multimodal activity patterns with
ultradian components and reduced activity levels. In contrast, the
individual daily profiles of aMT6s excretion and mean melatonin
synthesis followed a unimodal time pattern in all three strains,
suggesting that different output pathways of the SCN are responsible
for the temporal organization of locomotor activity and pineal
melatonin synthesis. In addition, melatonin synthesis at night and SCN
melatonin receptor density at day were significantly higher in BH and
LEW rats than in ACI rats. These results support the hypothesis of a
long-term stimulating effect of melatonin on its own receptor density
in the SCN.
6-sulphatoxymelatonin; pineal gland; suprachiasmatic nuclei; rat
strains; wheel running activity; ACI/Ztm; BH/Ztm; LEW/Ztm
