Journal of Neuroscience, Vol 13, 1057-1064, Copyright © 1993 by Society for Neuroscience
Heterozygosity at the canarc-1 locus can confer susceptibility for narcolepsy: induction of cataplexy in heterozygous asymptomatic dogs after administration of a combination of drugs acting on monoaminergic and cholinergic systems
E Mignot, S Nishino, LH Sharp, J Arrigoni, JM Siegel, MS Reid, DM Edgar, RD Ciaranello and WC Dement
Stanford University Sleep Disorders Center, Palo Alto, California 94304.
Narcolepsy is a genetically determined disorder of sleep characterized by
excessive daytime sleepiness and abnormal manifestations of REM sleep that
affects both humans and animals. Although its exact pathophysiologic
mechanisms remain undetermined, recent experiments have demonstrated that
in both humans and canines, susceptibility genes are linked with
immune-related genes. A striking difference, however, is that the genes
thought to be involved in the human pathology are autosomal dominant,
whereas canine narcolepsy in Dobermans is transmitted as a single autosomal
recessive gene with full penetrance (canarc-1). In this study, we have
examined the development of narcoleptic symptoms in homozygous narcoleptic,
heterozygous, and control Dobermans. Animals were behaviorally observed
until 5 months of age and then treated at weekly intervals with
cataplexy-inducing compounds that act on cholinergic or monoaminergic
systems (alone and in combination). Our data indicate that cataplexy can be
induced in 6- month-old asymptomatic heterozygous animals, but not in
control canines, with a combination of drugs that act on the monoaminergic
and cholinergic systems. This demonstrates that disease susceptibility may
be carried by heterozygosity at the canarc-1 locus. Our data further
suggest that cataplexy, a model of REM sleep atonia, is centrally regulated
by a balance of activity between cholinergic and monoaminergic neurons.