P1.12. EFFECTS OF LATERALIZED VISUAL STIMULATION ON MIDBRAIN DOPAMINERGIC NEURON ACTIVITY AND STRIATAL DOPAMINE RELEASE DYNAMICS
Martyna Marzec1,2, Karolina Nowalińska1, Tomasz Błasiak1
1 Jagiellonian University, Institute of Zoology and Biomedical Research, Department of Neurophysiology and Chronobiology, 9 Gronostajowa St., Cracow, Poland
2 Jagiellonian University, Doctoral School of Exact and Natural Sciences, 11 Łojasiewicza St., Cracow, Poland
INTRODUCTION: Ventral tegmental area (VTA) and substantia nigra pars compacta (SNc), plays a vital role in motor control and decision-making via dopamine release in the striatum. Asymmetries in striatal dopamine levels can bias action selection, leading to lateralized behaviours such as orienting or approach/withdrawal responses. Dopaminergic (DA) neurons integrate directional environmental cues, with the superior colliculi (SC) serving as a key sensory relay, particularly for visual input. While most studies have focused on the dominant, ipsilateral SC projections to the VTA/SNc, both mono- and polysynaptic contralateral connections exist, potentially contributing to lateralized dopaminergic responses.
AIM(S): We set out to characterise responses of DA neurons in the VTA/SNc to lateralized eye stimulation and investigate the resulting changes in striatal dopamine release on both sides of rat brain. We hypothesized that DA neuron responses depend on which eye receives the stimulus, leading to asymmetrical striatal dopamine release.
METHOD(S): To test our hypothesis in vivo extracellular single-unit recordings combined with SC disinhibition, and uniocular light stimulation were performed. Fiber photometry was employed to measure dopamine release in the striatum. We also conducted behavioural tests to assess the impact of optogenetic stimulation of the investigated pathway on orienting behaviours in rats.
RESULTS: Electrophysiological recordings revealed that uniocular stimulation predominantly evoked excitatory responses in DA neurons within the VTA/SNc. This effect showed a significant interaction with eye of stimulation, but no clear hemispheric asymmetry was observed. Fiber photometry revealed higher dopamine release in the striatum contralateral to the stimulated eye, compared to the ipsilateral site.
CONCLUSIONS: Our data suggest that lateralized sensory input can differentially modulate dopaminergic activity and striatal signalling, with implications for understanding sensory-driven action selection and motor control.
FINANCIAL SUPPORT: The National Science Centre, OPUS 17 2019/33/B/NZ4/03127