Syrian hamster. (Mesocricetus auratus) results in continuous mainte- nance ... 2#{176}C.All hamsters were supplied with food. (Wayne. Lab. Blox or Purina.
BIOLOGY
OF
35, 74-83
REPRODUCTION
Pineal
(1986)
Melatonin
Rhythms
Effects
of Photoperiod
JANET
in Female
M. DARROW,2
J.
MARILYN Worcester
and
Turkish Hibernation’
LAWRENCE
DUNCAN,4
and
Foundation
for
Shrewsbury,
Hamsters:
TAMARKIN,3
BRUCE
D. GOLDMAN4
Experimental
Biology24
Massachusetts
01545
and Clinical National
Psychobiology Branch3 Institute of Mental Health
Bethesda,
Maryland
20205
ABSTRACT Daily rhythms of pineal and serum melatonin content were characterized for adult female Turkish hamsters (Mesocricetus brandti) exposed to long days (16L:8D, 22#{176}C)or after transfer to short days (IOL:14D, 22#{176}C). The nocturnal peak of pineal melatonin content was found to be approximately 3 h greater in duration on short than on long days. Changes in levels of serum melatonin closely paralleled those of pineal melatonin. Thus, an effect of photoperiod on synthesis and secretion of pineal melatonin was demonstrated. In a separate experiment, female hamsters were induced to hibernate by exposure to a short-day, cold environment (1OL: 14D, 6#{176}C).During the 4 to por (body temperature
5-mo
37#{176}C). Little during torpor.
of
tonin
evidence However,
rhythms
absence
=
no
of pineal
appropriately
hibernation season, Turkish hamsters are 7-9#{176}C) alternating with 1 to 3-day intervals
nocturnal animals
different
in phase
melatonin
phased,
synthesis or secretion sampled during the first
output
rhythmic
or amplitude during
melato
from
torpor,
nm
the
signal
during
those pineal
number of seasonally breeding Goldman and Darrow, 1983; son and Watson-Whitmyre, cek,
1985;
sters
and
tion
of
critical veys
Tamarkinet in sheep, the
feature daylength
al., it has
nocturnal
1985).
pineal
of a pineal information
In Djungarian
proposed
that
melatonin
endocrine (Bittman
hamthe
peak
signal
durais the
which et
al.,
1983; 1984). unlike results
assay HD
15912
held
in females sampled bout displayed mela-
at 22#{176} C. Thus, Turkish
hamsters
despite
the
produces
an
of euthermia.
to pinealectomy, it was of interest daily rhythm of pineal melatonin con-
tent in this species on long vs. short days, for comparison with melatonin patterns already characterized in other species. Furthermore, since it has been suggested that pineal melatonin in mammals is secreted predominantly 1978),
Accepted November 12, 1985. Received August 12, 1985. ‘This research was supported by NIH Research Grant BDG. 2 Reprint requests: Janet M. Darrow, Ph.D., Worcester for Experimental Biology, 222 Maple Avenue, Shrewsbury,
in females of hibernating
Turkish hamsters to examine the
con-
Carter and Goldman, 1983a,b; Goldman et al., In the Turkish hamster (Mesocricetus brandti), other mammals tested to date, pinealectomy
melatonin was detected arousal from a torpor
of tor= 35-
in gonadal regression on long days, indicating that the pineal is required for maintenance of gonadal function (Carter et al., 1982). In contrast, removal of the pineal gland in the closely related Syrian hamster (Mesocricetus auratus) results in continuous maintenance of the reproductive system on long days and prevents short-day-induced reproductive regression (Reiter, 1978). Because of the unusual response of
to in a
mammals (Reiter, 1980; Karsch et al., 1984; Stet1984; lllnerova and Vane-
been
seen gland
intervals
INTRODUCTION The daily rhythm of pineal melatonin is known be a component of the photoperiodic mechanism
of pineal day after
known to display 4 to 8-day bouts of euthermia (body temperature
into the peripheral we utilized a recently for serum
melatonin
circulation developed to measure
(Rollag et al., radioimmunocirculating
of the hormone. Turkish hamsters hibernate when exposed short-day, cold environment in the laboratory and Goldman, 1980). The hibernation season
to
Foundation MA 01545.
74
levels to a (Hall is 4-5
MELATONIN
mo in bouts
duration of torpor
and is characterized (lasting 4-8 days)
ly
IN
TURKISH
Uteri
alternating and arousal
were
removed
Radioimmunoassay
(lasting 1-3 days). During torpor, core body temperature drops to as low as 7-9#{176} C, representing a substan-
formed
as
1979),
using
tial decline from body temperatures
generously
arousal. pineal tion, sured
To
the
35-37#{176}C range observed during
investigate
the
of euthermic intervals
of
of torpor
on
consequences
biosynthetic/secretory activity during hibernalevels of pineal and serum melatonin were meain hibernating hamsters during torpor and during
intervals
of arousal.
served those
The
in hibernating measured in
daily
melatonin
hamsters nonhibernating
were
profiles compared animals
obwith housed
at 22#{176}C.
the
adult
brandti) animals
were were
period 22 ± (Wayne
Turkish
hamsters
man
(Mesocricetus
obtained from our breeding colony. The raised from birth on a long-day photo-
(16L:8D, 2#{176}C.All Lab
water
lights hamsters
Blox
on
or
from were
Purina
0200 to supplied Chow
No.
1800 with
h) at food
5008)
and
on Long
I. Pineal and Short
Female monitored following
for
ranging this
in age
study.
by daily examination the method of Orsini
of the experiment, ted for the study days. This proportion
39% were
from
Estrous
1.5
to
further killed
43
was
of vaginal discharges (1961). At the onset
(60/15 3) of the females selecfound to be acyclic on long of anovulatory females is typi-
cyclic females were left All animals were checked
period of 5-6 by decapitation
which
al., was
hamsters
(2-4
mo
of
age)
wk, animals the night,
days
decapitated dim red
and pineals. and February.
at
were
were
using
using
melatonin
analog
by
antiserum
Brown
the
(Gold(Meloy
NJ) and R1055 Serum melatonin R1056,
by Dr. Rollag. Serum samples with 2.5 ml dichioromethane described
at
previously
1-melatonin
125
sampled
performed
as described
1984),
After
various times for collection
light,
Inc., Springfield, supplied by M. D. Rollag.
measured
(16L:8D).
Animals
assays
Foundation
et al.,
supplied extracted
on long
were under
melatonin
Laboratories, antiserum was
left
et
also
(300 p1) were according to a al.
(1983),
and
was determined by double antibody procedures (Darrow and Goldman,
3 mo
cyclicity
cal for our colony of Turkish hamsters. Thirty-one acyclic and 50 cycling females were transferred to a short-day light schedule (1OL:14D, lights from 0500-1500 h, 22#{176}C), and the remaining acyclic and day schedule.
et
R1055,
1986).
Days
hamsters
selected
per-
by Dr. M. D. Rollag.
melatonin content radioimmunoassay
Melatonin
weighed. was
(Tamarkin
antiserum
were
procedure
ad libitum.
Experiment
were
female
and
melatonin
previously
female
remainder
Worcester
Young
females
were selected for this study. Estrous cyclicity was not monitored in these females. Thirty-eight females were transferred to short days (1OL:14D, as above), and
Pineal Animals
pineal
II. Pineal and Serum on Long and Short Days
of trunk blood during January
METHODS
most
for melatonin
Seventy-three
during AND
from
described supplied
Experiment Melatonin
4-5
MATERIALS
75
HAMSTERS
on the daily
on 29
longfor a
wk, at which time they were at various times of day. At
Experiment III.Melatonin Rhythms During Hibernation Ninety selected
females for study.
ranging After
in age from 2-4 mo a 6-wk prior exposure
were to
short days transferred short-day
(1OL:14D, 22#{176}C),groups of females were to a cold room (6 ± 1#{176}C) with an identical photoschedule. Hamsters were housed
separately
in 48
containing
X
25
X
Absorb-Dri
21
cm
bedding
polycarbonate and
cages,
cotton
nesting
material. Individuals were checked for torpor each day at 2-4 hours before lights-off. Torpid hamsters were readily identified by their reduced respiration rate and lack of response to a puff of air detected at the
animal’s
back
(Hall
and
Goldman,
1980).
This
each time point, 2-8 females of each reproductive state were sampled on both long and short days. During the dark portion of the light/dark cycle, hamsters were killed under dim red illumination.
method of detecting torpor has been corroborated by telemetric recording of body temperature (Hall, 1981). Those individuals exhibiting torpor for at least
Pineals were vials on dry
tated at 4-h intervals, of torpor, or during
rapidly ice, then
excised stored
and frozen in at -20#{176}C until
separate assayed.
10
days
in
a preceding
20-day
interval
were
decapi-
either on Day 2 or 3 of a bout the first day after spontaneous
76
DARROW
arousal
from
collected
torpor.
as
in
Pineals
and
previous
trunk
studies.
blood
Some
(16/90) showed less than 10 days of torpor days of cold exposure. These females were nonhibernators, The
and
cold
March
room
were
portion
sampled
at
the
experiment
of
were
hamsters during 60 designated
3 times
of day. ran
from
6-week study. of “spontaneous”
Thus,
on
that
to short
long
days,
it appears
Statistical tests employed were chi square, linear gression analysis and one-way analysis of variance by the
Duncan
posteriori
test
for
exposure
despite acyclicity days
inhibited of female
reproductive activity in a significant Turkish hamsters (p< 0.01). Uterine
number weights
for
of the
sampled
most
females
in Table
whose 1. On each
weights of acyclic females were as compared to those of cycling
Analysis
lowed
came acyclic during the the rather high incidence
are presented
to July.
Data
ET AL.
pineals
were
photoperiod
uterine
significantly reduced hamsters (p