PINEALECTOMY BUT NOT MELATONIN SUPPLEMENTATION AFFECTS THE DIURNAL VARIATIONS IN ^I-MELATONIN BINDING SITES IN THE RAT BRAIN Sol Oaknin-Bendahan2, Yossi Anis1, Isaac Nir3 and Nava Zisapel1* 1
Department of Biochemistry The George S. Wise Faculty of Life Sciences Tel Aviv University Tel Aviv 69978, Israel 2 Department of Biochemistry University of La-Laguna Tenerife, Spain 3 Department of Pharmacology Hebrew University-Hadassah Medical School Jerusalem, Israel ABSTRACT
The distribution of melatonin binding sites in synaptosomal preparations fromfivebrain areas of sham-operated and pinealectomized young male rats (maintained in a 14 h light: 10 h darkness cycle; lights on at 5.00 h) was recorded at 10.00,18.00 and 24.00 h, 18 days after surgery, using 125I-melatonin as a probe. The densities of ^ - m e l a tonin binding sites in the medulla-pons, hippocampus and hypothalamus of the pinealectomized rats, exhibited clear diurnal variations. However, the densities of binding sites in these brain areas at 18.00 h were lower in the pinealectomized animals than at the other times of day tested, whereas in the sham-operated controls, the binding at 18.00 h was higher than at the other times of day. No diurnal variations were evident in the midbrain and cerebellum of the pinealectomized animals. The apparent affinities of the binding sites toward the ligand in the various brain areas were similar in the pinealectomized and sham-operated animals and did not significantly vary at any of the times recorded. Oral supplementation of * Author for correspondence
Accepted 3 July 1992
253 Brought to you by | University of Arizona Authenticated Download Date | 5/31/15 7:18 PM
Vol. 3, No. 3, 1992
Pinealectomy Affects
12i
1-Melatonin Binding
melatonin to the rats via drinking water had no effect on the diurnal variations in 125I-melatonin binding in the pinealectomized rat brain. The results indicate that the diurnal variations in 125I-melatonin binding sites in the rat brain are not generated by the pineal but are affected by removal of the gland.
KEYWORDS
melatonin, pinealectomy, receptor, brain, binding
INTRODUCTION
The nocturnal production of melatonin by the pineal gland and its release into the circulation provide a signal reflecting the changing environmental lighting cycle in the organism /l, 2/. By use of 2 - 1 iodomelatonin I-melatonin) as a probe, 'low affinity' melatonin binding sites (i.e. with an apparent K
Department of Biochemistry The George S. Wise Faculty of Life Sciences Tel Aviv University Tel Aviv 69978, Israel 2 Department of Biochemistry University of La-Laguna Tenerife, Spain 3 Department of Pharmacology Hebrew University-Hadassah Medical School Jerusalem, Israel ABSTRACT
The distribution of melatonin binding sites in synaptosomal preparations fromfivebrain areas of sham-operated and pinealectomized young male rats (maintained in a 14 h light: 10 h darkness cycle; lights on at 5.00 h) was recorded at 10.00,18.00 and 24.00 h, 18 days after surgery, using 125I-melatonin as a probe. The densities of ^ - m e l a tonin binding sites in the medulla-pons, hippocampus and hypothalamus of the pinealectomized rats, exhibited clear diurnal variations. However, the densities of binding sites in these brain areas at 18.00 h were lower in the pinealectomized animals than at the other times of day tested, whereas in the sham-operated controls, the binding at 18.00 h was higher than at the other times of day. No diurnal variations were evident in the midbrain and cerebellum of the pinealectomized animals. The apparent affinities of the binding sites toward the ligand in the various brain areas were similar in the pinealectomized and sham-operated animals and did not significantly vary at any of the times recorded. Oral supplementation of * Author for correspondence
Accepted 3 July 1992
253 Brought to you by | University of Arizona Authenticated Download Date | 5/31/15 7:18 PM
Vol. 3, No. 3, 1992
Pinealectomy Affects
12i
1-Melatonin Binding
melatonin to the rats via drinking water had no effect on the diurnal variations in 125I-melatonin binding in the pinealectomized rat brain. The results indicate that the diurnal variations in 125I-melatonin binding sites in the rat brain are not generated by the pineal but are affected by removal of the gland.
KEYWORDS
melatonin, pinealectomy, receptor, brain, binding
INTRODUCTION
The nocturnal production of melatonin by the pineal gland and its release into the circulation provide a signal reflecting the changing environmental lighting cycle in the organism /l, 2/. By use of 2 - 1 iodomelatonin I-melatonin) as a probe, 'low affinity' melatonin binding sites (i.e. with an apparent K
