Testing the hypothesis of the teleost dopaminergic ventral diencephalon as a homolog to the mammalian substantia nigra

Parkinson's disease is a neurological disorder that affects a patient's voluntary motor control through loss of dopamine signaling originating from the substantia nigra pars compacta. To discover more about the origins of the disease, this research attempted to replicate Parkinsonian deficits in an animal model using laser ablation of specific neurons. Previous research has shown potential homology of specific projection pathways from the zebrafish ventral diencephalon (vDC) to regions of the teleost brain to dopaminergic projections from the substantia nigra in the human brain. I used a transgenic line of zebrafish developed to express green fluorescence protein in cells with dopamine transporters and targeted specific diencephalic clusters in five-day old larvae using laser pulses. Bilateral ablation of the second diencephalic clusters within the vDC resulted in decreased spontaneous swimming activity, responses to visually-evoked startle stimuli, and responses to auditory-evoked startle responses. These effects are consistent with pharmacological lesions targeting the same neurons in zebrafish and add to evidence that the zebrafish vDC is functionally homologous to the mammalian substantia nigra.