Neuronal interactions involving cocaine- and amphetamine-regulated transcript (CART)-containing kisspeptin (KP), neurokinin B (NKB) and substance P (SP) neurons in the infundibular nucleus (Inf).

Neuropeptides exhibit variable colocalization patterns in neuronal cell bodies and fibers of the Inf (see color-coded captions). Single-, double- and triple-labeled peptidergic axons establish appositions onto other peptidergic neurons. Such appositions often involve CART-IR neuronal elements. The CART/KP/NKB triple-labeled cell body in A and B receives an axo-somatic afferent contact from a single-labeled CART-IR axon (green arrow in B). The CART/KP double-labeled cell body in C and D receives an afferent contact from a KP/NKB double-IR axon (purple arrows in D). A CART/SP double-IR neuron in E is innervated by KP-IR (red arrows) and KP/SP double-IR (purple arrow) axons. The dendrite of a GnRH neuron (brown pseudocolor) in F receives innervation from a CART/KP/NKB-IR triple-phenotype axon (white arrow). Scale bars = 20 µm in A, C, 12 µm in E and 10 µm in B, D and F.