Cannabinoids Shape Synaptic Activity and Adult Neurogenesis in the Zebrafish Pallium

Area of Science:

• Neuroscience
• Endocrinology
• Comparative Biology

Background:

• The endocannabinoid system's role in non-mammalian vertebrates is understudied.
• Zebrafish pallium governs cognitive functions and exhibits adult neurogenesis.
• Cannabinoid receptors, including CB1R, are present in the zebrafish pallium.

Purpose of the Study:

• To investigate the role of cannabinoid receptor type 1 (CB1R) in modulating synaptic activity and adult neurogenesis within zebrafish pallial circuits.
• To determine if CB1R influences neuronal remodeling and cognitive function-related brain regions in zebrafish.

Main Methods:

• Immunofluorescence and single-cell mRNA analysis to map CB1R expression in glutamatergic neurons of the dorsomedial (Dm) and dorsolateral (Dl) pallium.
• Electrophysiological recordings to assess the impact of CB1R antagonist rimonabant on synaptic transmission.
• Analysis of neural stem cell (NSC) proliferation and adult-born neuron maturation following phytocannabinoid and rimonabant treatments.

Main Results:

• CB1R is expressed in glutamatergic neurons in the Dm and Dl pallium.
• CB1R antagonism reduced spontaneous excitatory postsynaptic current frequency, indicating a tonic modulatory role in synaptic transmission.
• Phytocannabinoid exposure decreased NSC proliferation, while promoting adult-born neuron maturation, effects reversed by CB1R antagonism.

Conclusions:

• Cannabinoid signaling, mediated by CB1R, plays a significant role in regulating synaptic activity and adult neurogenesis in the zebrafish pallium.
• These findings suggest a conserved mechanism of neurogenesis control by the endocannabinoid system across vertebrate species.
• CB1R modulation impacts neuronal integration and plasticity in non-mammalian vertebrates.