Fig. 3.

Dark-field illumination micrographs of pro-TRH mRNA in the medial and periventricular parvocellular subdivisions of the hypothalamic PVN in fed (A) and fasted (B) animals and fasted animals receiving an intracerebroventricular infusion of α-MSH at a dose of 150 ng (C) or 300 ng (D) every 6 hr for 64 hr. Note the reduction in the accumulation of silver grains over the PVN in fasted animals compared with the fed controls. Fasted animals receiving 150 ng of α-MSH every 6 hr show suppression of pro-TRH mRNA in the PVN similar to that of fasted animals receiving artificial CSF. Fasted animals receiving 300 ng of α-MSH every 6 hr, however, show a marked increase in pro-TRH mRNA that is similar to that of fed control animals. III, Third ventricle. Scale bar, 100 μm.