Superficial grey layer of superior colliculus integrates visual cue-evoked learning and memory in rats: importance of TRPV3 ion channels

Abstract

The superficial grey layer (SuG) of the superior colliculus (SC) receives direct visual sensory inputs from the retina and V1 cortex to drive the motor command. Processing of information in this layer is known to mainly involve glutamatergic, GABAergic and cholinergic signalling systems. In addition, the occurrence of transient receptor potential vanilloid 3 (TRPV3) cationic channels has been detected in the superficial SC, but their functional significance has not been clarified. In our previous study, we have shown that SuG may play an important role in processing visual cues encoding reward information. Herein, we extend the scope of our study and probe the participation of TRPV3 channels in SuG neurons in visual cue-associated learning and memory. Rats were trained to self-administer food in an instrumental learning paradigm coupled with or without the light cues. The animals trained with the light cue showed a dramatic increase in lever press activity compared to those with no light. The SuG layer of the animals trained on light cue, showed an increase in the TRPV3-immunoreactivity in the neurons and upregulation of TRPV3 mRNA and protein expression. Bilateral administration of TRPV3 inhibitor isopentenyl pyrophosphate (IPP), directly in the SuG of trained rats, significantly reduced lever press activity. We suggest that TRPV3 channels in SuG may be involved in the formation of reward-related visual memory in rats.