AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 1 111-R115, Copyright © 1985 by American Physiological Society
Pineal gland influences period of circannual rhythms of ground squirrels
I. Zucker
Female golden-mantled ground squirrels were pinealectomized (Pinx) or
Sham-Pinx at 70 days of age and maintained for more than 2 yr at 23 degrees
C in a 10:14 light-dark photoperiod. Reproductive condition and body weight
were recorded weekly and bi-weekly, respectively. Pinx and Sham-Pinx
squirrels displayed circannual rhythms in body weight; the groups did not
differ with respect to absolute magnitudes of annual peaks and troughs in
body mass. The period of the circannual body weight cycle (measured peak to
peak) was 27 and 58 days shorter in Pinx than in Sham-Pinx squirrels during
the 1st and 2nd yr, respectively, after surgery. The onset of estrus during
the second postoperative cycle occurred significantly earlier in Pinx than
in Sham-Pinx squirrels. The pineal gland is not essential for the
generation or expression of circannual or circadian cycles but may affect
the period of some circannual rhythms.
