P116
Are photic shifts giving you a migraine? Try sumatriptan!
Priyoneel Basu , Joelle Baskerville , Micahel C. Antle
2
1
3
1Department of Psychology and Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, CANADA
2Department of Biological Sciences , University of Calgary, Calgary, Alberta, CANADA
3Department of Psychology, Hotchkiss Brain Institute and Department of Physiology and Pharmacology , University of Calgary, Calgary, Alberta,
CANADA
Light is the primary zeitgeber for the circadian system. Drugs that modify responses to light have the potential to disrupt
entrainment. Conversely, light-modifying drugs may also be exploited as chronobiotics to enhance or diminish to light. Serotonin
agonists generally attenuate light-induced phase shifts, largely through postsynaptic 5HT1A/7 receptors on SCN neurons and
presynaptic 5HT1B receptors on retinal terminals. Triptans are anti-migraine medications that act as agonist of the 5HT1B
receptor. The most commonly prescribed triptan is sumatriptan. Given its therapeutic activity at the 5HT1B receptor, we
hypothesized that this migraine medication would attenuate photic phase shifts. To test this hypothesis, we implanted male
hamsters with cannulas aimed at the SCN so that sumatriptan could be delivered to the SCN prior to a light pulse. Hamsters
pretreated in a counterbalanced fashion with either sumatriptan (150 µM or 1.5mM) or vehicle control (0.5µl, 0.9% saline) 15
minutes prior to a either a CT18 light pulse (15 minute, 40lux) or sham light pulse. Cannula placements were confirmed
histologically at the end of the study. Light pulses with saline pre-treatment caused phase advances (2.19 ± 0.12 h) that were
significantly attenuated by pretreatment with 150 µM sumatriptan (0.62 ± 0.32 h, p<0.05, paired t-test) and were completely
blocked by 1.5mM sumatriptan (-0.14 ± 0.06 h, p<0.000001, paired t-test). Neither saline nor 1.5mM sumatriptan elicited phase
shifts on their own (0.06 ± 0.02 h and -0.1 ± 0.09 h respectively). These data suggest that sumatriptan may modify circadian
responses to light, and could be used as a chronobiotic to attenuate responses to light exposure at inappropriate times of the day