Immunocytochemistry of luteinizing hormone-releasing hormone and sexual maturation of the frog brain: comparisons of juvenile and adult bullfrogs (Rana catesbeiana).

An unlabeled antibody enzyme immunocytochemical procedure has been combined with an adjacent serial section approach to localize mammalian-like immunoreactive luteinizing hormone-releasing hormone (ir-LH-RH) in brains of juvenile and adult bullfrogs (Rana catesbeiana). In juvenile animals modest specific immunocytochemical staining was found over cell bodies in the anterior preoptic area (aPOA) and in scattered neurosecretory endings in the outer layer of the median eminence (ME). In brains of adults, a comparatively robust staining was observed for perikarya in the medial septal nucleus, as well as in the aPOA; intense immunostaining of a well-differentiated ME also was noted for adults. Specific immunocytochemical staining was absent from other brain regions and in control preparations. Accordingly, changes both in the number and distribution of cells stained and in the quality of immunostaining were coincident with sexual maturation of the brain. This initial study of juvenile and adult bullfrogs suggests that ir-LH-RH in septal and preoptic areas may exert distinctly differing activities.