Changes in populations of LHRH-immunopositive cell bodies following gonadectomy.

One day after castration of male rats, plasma LH rose and the number of LHRH immunopositive neuronal perikarya decreased. As plasma LH continued to rise six days and three weeks post-castration, the number of LHRH immunopositive neurons also increased. The largest population of LHRH immunopositive neurons was detected three weeks post-castration and the cell group that showed the greatest increase was in the rostral preoptic area. In females, the largest population of LHRH immunopositive neurons was observed one day post-ovariectomy; at this time plasma LH levels were not significantly elevated above diestrous levels. Six days post-ovariectomy, LH levels were elevated and the number of LHRH immunopositive cells decreased. As LH levels continued to rise three weeks post-ovariectomy, the population increased in size. In males, primarily LHRH cells of the rostral preoptic area increased in in number; in females, the cell groups that increased were scattered over the diagonal band of Broca, preoptic and anterior hypothalamic areas. Although LHRH neurons demonstrated these variations following gonadectomy, there was no evidence of alteration(s) in molecular processing of precursor hormone.