Effect of time-of-day on the yawning response to apomorphine in normal subjects.
The yawning response to the dopamine (DA) receptor agonist apomorphine HCl (Apo, 7 microg/kg s.c.) and placebo (physiological saline) were examined in two groups of normal men. One group (n = 11) was investigated in the morning and the other group (n = 16) in the afternoon. The frequency of yawning was polygraphically monitored for 60 min following injection. Apo increased yawning compared with placebo when given in the morning (p < 0.02), but not when given in the afternoon. Yawning frequency was increased after both Apo (p < 0.01) and placebo (p < 0.025) when given in the morning compared with responses in the afternoon. These results suggest that yawning frequency with both Apo and placebo is influenced by time of day, possibly as a result of diurnal variation in DA receptor sensitivity.
Lal
S
S
Douglas Hospital Research Center, Verdun, Canada.
Tesfaye
Y
Y
Thavundayil
J X
JX
Skorzewska
A
A
Schwartz
G
G
D000328:Adult; D001058:Apomorphine / Q000008:administration & dosage*; D002940:Circadian Rhythm / Q000502:physiology*; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D006801:Humans; D007568:Jaw / Q000502:physiology; D008280:Magnetics; D008297:Male; D012016:Reference Values; D016037:Single-Blind Method; D015000:Yawning / Q000187:drug effects* / Q000502:physiology
D001058:Apomorphine