Brain dopamine receptor levels elevated in canine narcolepsy.

Concentrations of dopamine D2 receptors in discrete brain areas differed significantly between dogs with the genetically transmitted form of narcolepsy, and age- and breed-matched controls. D2 receptors were assayed and quantified with Scatchard analysis using [3H]spiperone. Receptor densities in the nucleus accumbens, rostral caudate, and amygdala were consistently higher in narcoleptic animals. In amygdala, dopamine receptor abnormalities were associated with elevated dopamine and 3,4-dihydroxyphenylacetic acid concentrations, but no change in 3-methoxytyramine or homovanillic acid concentrations. These data indicate mesolimbic system involvement in canine narcolepsy and point to impaired dopamine release as a possible etiologic factor.