Reduction of dopamine synaptic activity: degradation of 50-kHz ultrasonic vocalization in rats.
Vocal deficits are prevalent and debilitating in Parkinson's disease. These deficits may be related to the initial pathology of the nigrostriatal dopamine neurons and resulting dopamine depletion, which contributes to dysfunction of fine motor control in multiple functions. Although vocalization in animals and humans may differ in many respects, we evaluated complex (50-kHz) ultrasonic mate calls in 2 rat models of Parkinson's disease, including unilateral infusions of 6-hydroxydopamine to the medial forebrain bundle and peripheral administration of a nonakinesia dose of the dopamine antagonist haloperidol. We examined the effects of these treatments on multiple aspects of the acoustic signal. The number of trill-like (frequency modulated) 50-kHz calls was significantly reduced, and appeared to be replaced by simpler (flat) calls. The bandwidth and maximum intensity of simple and frequency-modulated calls were significantly decreased, but call duration was not. Our findings suggest that the nigrostriatal dopamine pathway is involved to some extent in fine sensorimotor function that includes USV production and complexity.