Changes in dendritic spine density in the preoptic area of the female rat at puberty

Preoptic area (POA) neurons stained by a modification of the Golgi-Kopsch method were studied in developing female rats. Particular attention was focused on dendritic spine densities as they might be altered in relation to the onset of puberty. Neurons in the anterior superior and posterior superior portions of the POA showed an increase in mean spine density at the age of vaginal opening. The increase in dendritic spine density in the posterior inferior quadrant of POA occurred prior to vaginal opening. The entire posterior POA maintained peak levels of spine numbers through 55 days of age, but then exhibited a dramatic drop at 75 days. Thus, modification of the neuropil may well continue at least to this age. The increases in spine densities at vaginal opening for the superior POA quadrants, followed by relatively stable values, appear to implicate these areas in the timing of the onset of puberty.