Endocannabinoid Signaling from 2-Arachidonoylglycerol to CB 1 Cannabinoid Receptor Facilitates Reward-based Learning of Motor Sequence

• Published in: Neuroscience Vol. 421; p. 1
• Main Authors: Tanigami, Hayate, Yoneda, Mitsugu, Tabata, Yuki, Echigo, Ryosuke, Kikuchi, Yui, Yamazaki, Maya, Kishimoto, Yasushi, Sakimura, Kenji, Kano, Masanobu, Ohno-Shosaku, Takako
• Format: Journal Article
• Language: English
• Published: United States 21.11.2019
• Subjects: Endocannabinoid system; Reversal learning; Reinforcement learning; Lever press
• ISSN: 1873-7544

The endocannabinoid system modulates synaptic transmission, controls neuronal excitability, and is involved in various brain functions including learning and memory. 2-arachidonoylglycerol, a major endocannabinoid produced by diacylglycerol lipase-α (DGLα), is released from postsynaptic neurons, retrogradely activates presynaptic CB cannabinoid receptors, and induces short-term or long-term synaptic plasticity. To examine whether and how the endocannabinoid system contributes to reward-based learning of a motor sequence, we subjected male CB -knockout (KO) and DGLα-KO mice to three types of operant lever-press tasks. First, we trained mice to press one of three levers labeled A, B, and C for a food reward (one-lever task). Second, we trained mice to press the three levers in the order of A, B, and C (three-lever task). Third, the order of the levers was reversed to C, B, and A (reverse three-lever task). We found that CB -KO mice and DGLα-KO mice exhibited essentially the same deficits in the operant lever-press tasks. In the one-lever task, both strains of knockout mice showed a slower rate of learning to press a lever for food. In the three-lever task, both strains of knockout mice showed a slower rate of learning of the motor sequence. In the reverse three-lever task, both strains of knockout mice needed more lever presses for reversal learning. These results suggest that the endocannabinoid system facilitates reward-based learning of a motor sequence by conferring the flexibility with which animals can switch between strategies.