Long-term ovariectomy attenuates several neuroendocrine-dependent changes in reproductive function of aging female rodents, but the sites affected and underlying mechanisms are not known. This study was designed to identify effects of aging on hypothalamic-preoptic neurocytoarchitecture and to determine whether long-term ovariectomy attenuated any of those changes. Coronal sections from midportions of the preoptic area (POA), suprachiasmatic nucleus (SCN) and arcuate nucleus (ARC) were examined by quantitative light microscopy in young (5 month) and old (18-20 months) intact mice and in old mice which had been ovariectomized at 6 months of age. Neuronal density in old intact mice decreased in both ARC and POA (30%; p less than 0.05), but no significant decrease occurred in SCN. Total perikaryal area decreased only in ARC (10%; p less than 0.05), while area of perikaryal nuclei did not change in any region. Area of nucleoli increased (13%; p less than 0.005) in all three regions of old intact and old ovariectomized mice. Neither density nor size of glia changed with age. Density of blood vessels increased strikingly in ARC (150%; p less than 0.05), and in POA (30%; p less than 0.05), but not significantly in SCN of old mice. Long-term ovariectomy did not prevent any of these changes; indeed, it promoted the decline of neuronal density in SCN (40%; p less than 0.05) and neuronal area (15%; p less than 0.05) in POA. Reductions in neuronal density were not explained by expansion of the SCN or peri-ARC or peri-POA regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMedDate not supplied

Loss of LH-RH neurons in the rostral forebrain of old female C57BL/6J mice.

This study reports the quantitative immunohistochemical distribution of luteinizing hormone-releasing hormone (LH-RH) neurons within the rostral forebrain of young (5-6 month) and old (26-28 month) C57BL/6J mouse. Old mice demonstrated a significant (18%) loss of LH-RH-containing neurons (p less than 0.001, ANOVA). The most striking losses involved the preoptic area (24%) and more rostral regions (26%). The presence of pituitary or mesenteric tumors in older mice did not affect the density of LH-RH neurons. These observations indicate that LH-RH neurons comprise part of the neuronal population previously reported to be reduced in the preoptic area of older mice (4).

Aging↗