Assessment of spontaneously occurring periodic limb movements in sleep in the rat.
OBJECTIVE
Periodic limb movements in sleep (PLMS) are often associated with the restless legs syndrome (RLS). Although the dopaminergic system seems to be involved, the pathophysiology of PLMS and RLS is still obscure. The objective of this study is to explore whether a PLMS-like phenomenon can be observed in rodents in order to elucidate the underlying mechanisms.


METHODS
In a group of young and old rats (1.4-1.6 and 16.2-20.5 months, respectively), sleep-wake behavior was recorded and hindlimb movements were detected by means of a magneto-inductive device during two 12-h light periods. Furthermore, in the old rats, recordings were made after administration of the dopamine antagonist haloperidol (HAL) on three consecutive days. Periodic hindlimb movements (PHLM) during nonrapid eye movement sleep (NREM) were identified according to modified human criteria.


RESULTS
In the young animals, no PHLM were observed, whereas, 4 out of 10 old rats showed PHLM, two of them have more than 5 PHLM/h. Haloperidol affects neither the sleep pattern nor the number of PHLM. Interestingly, the percentage of old rats spontaneously displaying PHLM resembles the prevalence of PLMS in the elderly.


CONCLUSIONS
Our study demonstrates for the first time that periodic hindlimb movements (PHLM) in sleep can occur spontaneously in rats. A clear effect of age on this phenomenon was seen, with only old animals displaying PHLM. To validate whether the observed PHLM constitute a good model for human PLMS or even RLS, their pharmacological properties need to be characterized in a large number of PHLM positive animals.
Baier
Paul Christian
PC
Sleep Pharmacology, Max-Planck-Institute of Psychiatry, Kraepelinstr. 2-10, 80804 Munich, Germany. pbaier@gwdg.de
Winkelmann
Juliane
J
Höhne
Arnold
A
Lancel
Marike
M
Trenkwalder
Claudia
C
D000375:Aging / Q000502:physiology; D000818:Animals; D018726:Anti-Dyskinesia Agents / Q000494:pharmacology; D006220:Haloperidol / Q000494:pharmacology; D006614:Hindlimb / Q000502:physiology*; D008297:Male; D009068:Movement / Q000187:drug effects / Q000502:physiology*; D010507:Periodicity; D051381:Rats; D017208:Rats, Wistar; D012890:Sleep / Q000187:drug effects / Q000502:physiology*
D018726:Anti-Dyskinesia Agents; D006220:Haloperidol