Fig. 1.

(A) Hierarchical depiction of synaptic connections allowing information flow among neuropeptidergic neurons in the arcuate mucleus and lateral hypothalamus. Lep-Rb denotes leptin receptor expression by neurons in the arcuate nucleus. (B) Orexin-containing neurons receive predominantly excitatory synaptic inputs in lean mice. (pink: inhibitory/GABA synapse; green: excitatory/glutamate synapse; red rectangles pinpoint CB₁ cannabinoid receptors). (B₁) In obesity, orexin-containing neurons up-regulate DAGLα to block surplus inhibition by retrograde endocannabinoid signals.