A nonphotic stimulus inverts the diurnal-nocturnal phase preference in Octodon degus.
J Neurosci
; 19(1): 328-33, 1999 Jan 01.
Article
in En
| MEDLINE
| ID: mdl-9870962
ABSTRACT
Mechanisms differentiating diurnal from nocturnal species are thought to be innate components of the circadian timekeeping system and may be located downstream from the circadian pacemaker within the suprachiasmatic nucleus (SCN) of the hypothalamus. In the present study, we found that the dominant phase of behavioral activity and body temperature (Tb) is susceptible to modification by a specific modality of behavioral activity (wheel-running activity) in Octodon degus, a mammal that exhibits multiple chronotypes. Seven Octodon degus exhibited diurnal Tb and locomotor activity (LMA) circadian rhythms while entrained to a 24 h light/dark cycle (LD 1212). When the diurnal animals were provided unrestricted access to a running wheel, the overt daily rhythms in these animals inverted to nocturnal. This nocturnal pattern was sustained in constant darkness and returned to diurnal after removal of the running wheel. Six additional animals exhibited nocturnal chronotypes in LD 1212 regardless of access to running wheels. Wheel-running activity inverted the phase preference in the diurnal animals without changing the 24 hr mean LMA or Tb levels. Because wheel running did not increase the amplitude of the pre-existing diurnal pattern, simple masking effects on LMA and Tb cannot explain the rhythm inversion. The diurnal-nocturnal inversion occurred without reversing crepuscular-timed episodes of activity, suggesting that diurnal or nocturnal phase preference is controlled separately from the intrinsic timing mechanisms within the SCN and can be dependent on behavioral or environmental factors.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Rodentia
/
Running
/
Choice Behavior
/
Circadian Rhythm
Aspects:
Patient_preference
Limits:
Animals
Language:
En
Journal:
J Neurosci
Year:
1999
Document type:
Article
Affiliation country: