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Author (up) Deveson, Sharon L; Arendt, Josephine; Forsyth, Isabel A url  doi
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  Title Sensitivity of Goats to a Light Pulse During the Night as Assessed by Suppression of Melatonin Concentrations in the Plasma Type Journal Article
  Year 1990 Publication Journal of Pineal Research Abbreviated Journal  
  Volume 8 Issue 2 Pages 169-177  
  Keywords animals; goat; Circadian Rhythm; Light intensity  
  Abstract This study investigates the ability of a 1 h light pulse of different intensities at night to suppress plasma melatonin in goats. Six female Saanen dairy goats, about 2 yr old, were housed in a light-tight shed. The goats were habituated for 1 wk to an 8L: 16D photoperiod (40.70 ± 4.16 &#956;W/cm2; 137 ± 14 lux), lights on 0800 h. A 1 h light pulse, of different intensity on each occasion, was given from 1900 to 2000 h. Light intensity was measured by using a lux meter (mean of 36 measurements at goat's eye level). Five different light intensities were given during December in the order 4.22 ± 0.62 &#956;W/cm2 (14.2 ± 2.1 lux), 0.68 ± 0.09 &#956;W/cm2 (2.3 ± 0.3 lux), 0.26 ± 0.004 &#956;W/cm2 (O.87 ± 0.14 lux), darkness, 40.70 ± 4.16 &#956;W/cm2 (137 ± 14 lux), with 1–3 d between treatments. The goats were bled hourly from 1500 to 1900 h and every 15 min from 1900 to 2100 h, and a last bleed occurred at 2200 h. Dark-phase samples were taken in dim red light (<0.03 &#956;W/cm2; 0.1 lux). Plasma was assayed for melatonin by radioimmunoassay. Suppression of melatonin concentrations increased as light intensity increased as follows: Darkness, 0%; 0.26 ± 0.004 &#956;W/cm2; 0%; 0.68 ± 0.09 &#956;W/cm2; 43.1%; 4.22 ± 0.62 &#956;W/cm2, 71.1%; 40.70 ± 4.16 &#956;W/cm2, 81.2%. Suppression was significant (P<0.05) at light intensities >0.68 &#956;W/cm2, 2.3 lux. A hyperbolic relationship existed between percent suppression and light intensities.  
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  Call Number LoNNe @ schroer @ Serial 1585  
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