Endocannabinoid signaling in the amygdala: anatomy, synaptic signaling, behavior, and adaptations to stress.

(a) Schematic diagram depicting the regional heterogeneity in the expression of the molecular components of eCB signaling between different amygdala subnuclei. The localization of DAGLα, CB1 receptors, FAAH and MGL are depicted based on data summarized in the in the text. (b) Left top inset: diagram of the amygdala with simplified cellular organization. BLA projection neuron in black, GABAergic interneuron in yellow, and glutamatergic inputs in grey. Boxed area is expanded in the main figure. Synaptic localization of eCB signaling components in a schematized BLA neuron receiving synaptic inputs from a GABAergic interneuron, and glutamatergic input from the external capsule. Known forms of eCB-mediated synaptic signaling at these synapses are overlaid, and specific eCB ligands noted where data is available.

A highly simplified schematic diagram of a common eCB signaling motif expressed across different cortical territories and their associated parallel cortico-striato-pallidal circuits. In “motor” circuits, cortical glutamatergic pyramidal cells (red), synapse onto striatal neurons, and are subject to eCB-mediated retrograde suppression of glutamate release (indicated by green line). GABAergic (black) striatal neurons send projections to the globus pallidus, which is also subject to eCB-mediated retrograde suppression of GABA release. Thus, each stage of the motor circuit is modulated by eCB signaling. A similar motif is evident within “limbic” cortical regions such as the PFC, and we suggest a similar motif may exist within the amygdala circuit. These limbic parallel circuits also exhibit a high degree of interaction, as indicated by the cross projections between and from, the PFC and BLA. (?) Indicates lack of experimental data.