Figure 3.

(A) Magnocellular oxytocin neurons are inhibited by icv injections of α-MSH and this effect can be blocked by pre-administration of a CB1 cannabinoid antagonist (Sabatier et al., 2003). (B) Oxytocin secretion from the posterior pituitary gland is reduced by icv injection of MC4 agonists. (C) However, α-MSH and MC4 agonists induce Fos expression in magnocellular oxytocin neurons and (D) induce dendritic oxytocin release. (E) Application of α-MSH retrodialysis to the SON affects the electrical activity of VMN neurons in vivo. Mean change in firing rate (±SE) in VMN neurons that were not affected (open bars; n = 13), and activated (solid bars; n = 8; P < 0.005, 0–30 min vs. control) in the 30 min period from the start of α-MSH infusion (100 μM) on the SON.