Postnatal apoptosis, development, and sex difference in the lateral septum of rats

Abstract

To determine whether apoptosis is involved in the formation of the structure and morphological sex difference of the lateral septum (LS), the postnatal developmental changes in the number of apoptotic cells were examined in the LS on postnatal day 1 (PD1 = birth day), 4, 6, 8, 11, 16, and 31 in male and female rats. Apoptotic cells were immunohistochemically detected by antibody against single-stranded DNA (ssDNA) or active caspase-3. The volume of the LS was also measured and was found to increase with age. The number of apoptotic cells detected by anti-ssDNA in the LS increased from PD1 to PD8 but decreased after PD11. Also, the LS was divided into dorsal, intermediate, and ventral parts (LSd, LSi, and LSv), and the volume and number of ssDNA-immunoreactive cells in each part were measured on PD6, 8, 11, 16, and 31. In both sexes, a large number of ssDNA-immunoreactive cells was found in the LSd and LSi on PD8 (but not on PD6) and in the LSv on PD6 and PD8. On PD6, the number of active caspase-3-immunoreactive cells was significantly greater in the LSv than in the LSd or LSi, in both sexes. Only the LSi of males had a high number of ssDNA-immunoreacitve cells on PD16; the number was significantly greater than that of females of the same age. However, there was no significant sex difference in the number of active caspase-3-immunoreacitve cells in the LSi on PD16. On PD31, the volume of the LSi was significantly greater in females than in males. There was no sex difference in volume or number of apoptotic cells in the LSd or LSv. These findings indicate that loss of cells due to apoptosis, which is partially caused by activation of caspase-3, occurs in the LS during postnatal development, with regional differences. They also indicate that sex difference in caspase-3-independent apoptosis contributes to morphological sexual differentiation of the LSi.

Fetal Jaw Movement Affects Condylar Cartilage Development

“…Sections were prepared as described previously (Hatta et al, 2002). Apoptotic cells were detected with polyclonal rabbit anti-singlestranded DNA (ssDNA) antibody (DAKO Japan, Kyoto, Japan) in the condylar cartilage at E18.5 (Nd = 4, Ne = 4) (Tsukahara et al, 2004).…”

Sex differences in adult cell proliferation within the zebrafish (Danio rerio) cerebellum

“…Recently, it has been suggested that the number of newly generated cells reaching the adult anterior accessory olfactory bulb is also sexually differentiated, with male rats exhibiting higher numbers of newborn cells (Peretto et al, 2001). In addition to neurogenesis and cell survival, it has been suggested that sex differences in cell numbers in several neural structures develop through sex-steroid-sensitive mechanisms that regulate apoptosis (Nordeen et al, 1987;Kirn & DeVoogd, 1989;Kirn & Schwabl, 1997;Stokes et al, 2004;Tsukahara et al, 2004).…”

Neuroanatomy and sex differences of the lordosis-inhibiting system in the lateral septum

“…Additionally, control of cell number by apoptotic cell death contributes to creating sex differences in cell number in several SDNs (Forger, 2009; Tsukahara, 2009). We found that the number of apoptotic cells in the male LSi is larger than that of the female LSi on PD16 (Tsukahara et al, 2004). The sex difference in the loss of cells by apoptosis during the late postnatal period is a contributing factor for producing the sex difference in neuron number of the LSi in adulthood.…”

“…The LSi is one of the SDNs in the rat brain. The volume of the LSi in prepubertal female rats is larger than that of same-aged male rats, however, there are no sex differences in the volume of the LSd and LSv (Tsukahara et al, 2004). The number of LSi neurons in adult female rats is greater than that in adult male rats, while there are no sex differences in the number of neurons in the LSd and LSv (Segovia et al, 2009).…”

“…This finding suggests that androgens have an effect during the neonatal to prepubertal periods and are necessary for the formation of the male-typical structures of the LSi. The sex difference in LSi volume of rats is found on PD31, but not on PD16 (Tsukahara et al, 2004), indicating that this sex difference emerges during the prepubertal period between PD16 and PD31. Additionally, control of cell number by apoptotic cell death contributes to creating sex differences in cell number in several SDNs (Forger, 2009; Tsukahara, 2009).…”