Table 1.

Characterization of oropharyngeal dysphagia in rodent models of Parkinson’s disease.

Author (Year)	Animal/Sex, Age or BW	Method Inducing Dysphagia	Main Defects	Dysphagia Screening
				Methods (Tools)	Results
Ciucci et al. (2010) [11]	Rat/male, 4–6 months old	Unilateral infusion of 6-OHDA into the medial forebrain bundle	Degeneration of dopamine neurons; vocalization deficits	·Ultrasonic vocalization analysis	·The complexity, intensity and bandwidth diminish in unilateral 6-OHDA model.
Ciucci et al. (2011) [12]	Rat/male, 9 months old	Unilateral infusion of 6-OHDA into the medial forebrain bundle	Degeneration of dopamine neurons	·Tongue motility assessment	·Maximal and average tongue force was significantly diminished and average tongue press time was significantly longer after unilateral infusion of 6-OHDA.
Kane et al. (2011) [13]	Rat	Unilateral infusion of 6-OHDA into the medial forebrain bundle	Degeneration of presynaptic dopaminergic striatal neurons	·Ultrasonic vocalizations analysis ·Pasta biting	·The parkinsonian animals have markedly lower bite strength and irregular intervals between bites. ·The parkinsonian animals took about twice as long to consume a single piece of pasta as the control animals.
Nuckolls et al. (2012) [14]	Rat/male, 3 months old	Unilateral or bilateral infusion of 6-OHDA into the medial forebrain bundle	Depletion of dopamine	·Lick assay	·Both unilateral and bilateral nigrostriatal dopamine depletion decrease tongue force during licking. ·Tongue motility is decreased following unilateral but not bilateral nigrostriatal dopamine depletion.
Russell et al. (2013) [15]	Rat/male, 9 months old	Unilateral infusion of 6-OHDA into the medial forebrain bundle	Degeneration of presynaptic dopaminergic striatal neurons	·VFSS	·Parkinsonian group had significantly more aberrant movement than the healthy young adult and old groups. ·Parkinsonian group had significantly smaller bolus areas compared with both the young adult and old groups.
Grant et al. (2015) [16]	Rat/2, 4, 6, and 8 months old	Mutations to the Pink1 (PINK1-/- rats)	Progressive vocalization and oromotor deficits	·Ultrasonic vocalization analysis ·Lick force and rate ·Pasta biting	PINK1-/- rats ·Developed early and progressive vocalization and oromotor deficits. ·Had significantly reduced loudness (intensity) as early as 2 months of age. ·Had significantly reduced peak frequency at 6 and 8 months compared to both 2 and 4 months. ·Pressed with a greater amount of force compared to controls during the licking task. In addition to overshooting, the target PINK1-/- rats also had more variable lick forces compared to controls. As the PINK1-/- rats aged, their lick force pattern changed. ·Had more irregular and inconsistent biting patterns leading to increased inter-bite intervals.
Cullen et al. (2018) [17]	Rat/male, 4 months old	Mutations to the Pink1 (PINK1-/- rats)	Progressive vocalization and oromotor deficits	·VFSS	Pink1-/- rats ·Had significantly increased the average and maximum bolus size at both 4 and 8 months. ·Had significantly increased velocities compared to WT at 8 months. ·Had a significant reduction in mastication rate for at 8 months.
Gould et al. (2018) [18]	Rat/male and female, 14 weeks old	Daily IP injections of the rotenone emulsification	Debilitative behaviors (akinesia and lack of feeding)	·VFSS	·A significant effect of injection with rotenone, regardless of dose level, was found for rostrocaudal mandibular range of motion, duration of chewing cycle, duration of jaw closing, and time of tongue rostralmost movement.

6-OHDA, 6-hydroxydopamine; BW, body weight; IP, intraperitoneal injection; PINK1, PTEN-induced putative kinase 1; VFSS, videofluoroscopic swallowing study; WT, wild type.