With a recently developed microdissection technique, four circumventricular organs were removed from the rat brain, and their contents of LHRH and TRH were measured. The subfornical organ, the organon vasculosum lamina terminalis, the subcommissural organ, and the area postrema all contained significant quantities of both releasing factors. The concentration of LHRH in the organon vasculosum (OVLT) was 14 ngâ mg protein, 58% of that found in the median eminence. The concentration of LHRH in the remaining circumventricular organs ranged from4.2 to 10.2 ngâ mg protein. The concentration of TRH in these structures, however, was consid rably lower, ranging from 0.7 to 1.8 ngâ mg protein. The concentrations of LHRH and TRHin the tissue immediately adjacent to the organon vasculosum were nearly 50 times and 4 timesless, respectively, than the concentration of these two releasing factorswithin the OVLT itself.
ASJC Scopus subject areas