Brain-Physiological and Pharmacological Studies on the Effect of the Light on the Secretion of Prolactin in Goats

• Project/Area Number: 60560270
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: 畜産学(含草地学)
• Research Institution: Faculty of Agriculture, Iwate University
• Principal Investigator: SUGAWARA Haku Professor, Faculty of Agriculture, Iwate University, 農学部, 教授 (30003742)
• Co-Investigator(Kenkyū-buntansha): SHIGA Akio Associate Professor, Faculty of Agriculture, Iwate University, 農学部, 助教授 (20003783)
• Project Period (FY): 1985 – 1986
• Project Status: Completed (Fiscal Year 1986)
• Budget Amount: ¥2,000,000 (Direct Cost: ¥2,000,000); Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000); Fiscal Year 1985: ¥1,500,000 (Direct Cost: ¥1,500,000)
• Keywords: Goat / Prolactin(PRL) / Electroencephalogram(EEG) / EEG power spectrum / 消灯 / 光

Research Abstract

Two experiments were carried out with non-lactating Saanen goats to clarify the effects of the light and five drugs on the plasma prolactin(PRL) concentration and the electroencephalogram(EEG). For convenience sake, the <delta> , <theta> , <alpha> and <beta> bands of the EEG power spectrum were set in a range of 1.26-3.75, 3.76-7.50, 7.51-15.00 and 15.01-30.00 Hz, respectively.
Experiment I. On the control day, plasma PRL concentration rose rapidly in goats after the light was turned off at 8:00 p.m. On the experimental day, when the light was turned off at midnight, it did not rise in the same goats before midnight, but rose in them after the light was turned off. On the EEG, the cumulative time of appearance of low amplitude fast waves(FW) increased and the ratio of the <theta> band of the power spectrum decreased after the light was turned off at 8:00 p.m. on the control day. On experimental day, however, the ratios of FW and the bands of the power spectrum on the EEG remained unchan ged until midnight, but changed after the light was turned off at midnight.
Experiment II. In experiment II, l-dopa was infused into the external jugular vein of some goats in an amount of 10 <micro> g per kilogram of body weight per minute for 3 hours. Serotonin, 5-hydroxytryptophan (5-HTP), melatonin and reserpine were infused into the external jugular vein of other goats in an amount of 0.5, 3.0, 0.01 and 0.01 mg per kilogram of body weight, respectively. 1. When l-dopa was administered, it did not rise of plasma PRL concentration after the light was turned off and the ratio of <theta> band of the power spectrum increase, but the ratio of the <beta> band decreased. 2. When serotonin was administered under light condition, plasma PRL concentration rose and the ratio of the <delta> band of the power spectrum increased, but the ratio of the <beta> band decreased. These effects may have been induced secondarily by the circulatory reaction. 3. When 5-HTP was administered under light condition, plasma PRL concentration rose markedly and the ratio of <delta> band of the power spectrum increased, but the ratio of <beta> band decreased. 4. When melatonin was administered under light condition, plasma PRL concentration rose rapidly and markedly, but the ratio of the bands of the power spectrum did not changed. 5. When reserpine was administered under light condition, plasma PRL concentration rose rapidly and was soon reduced slightly. It remained, however, at a level higher than the control one for 24 hours after administration. It rose again after the light was turned off, in addition to a high basal level caused by reserpine administration. The <delta> band of the power spectrum increased, but the <theta> and <alpha> bands decreased in ratio under dark condition.