Incongruent pattern of neurokinin B expression in rat and mouse brains

Abstract

The expression patterns of Tac2 and NK3 mRNA and of pep2, the neurokinin B (NKB) precursor protein, were compared in rats and mice. Pep2 immunoreactivity was observed in fibers, terminals, and perikarya in the brains of both species, but the number of NKB-immunoreactive cells was generally smaller in mice than in the corresponding nuclei in rats. Congruent distribution patterns of Tac2 mRNA and NKB were found in many nuclei of the thalamus and hypothalamus (habenula, anterodorsal nucleus, preoptic area, arcuate nucleus, paraventricular nucleus). However, mice expressed Tac2 mRNA neither in the hippocampus nor in the nucleus of the lateral olfactory tract, in contrast to rats. Accordingly, mice showed no NKB in the projection areas of these nuclei, such as the olfactory tubercle, whereas a clear NKB signal was present in rat tissues. Surprisingly, we found nearly identical NK3 mRNA expression patterns in both species, despite the species differences in NKB expression. Thus, although the expression patterns of Tac2 and NKB are similar in rats and mice, noteworthy differences exist. Our results have important implications for the interpretation of behavioral results concerning the NKB/NK3 system in these species.

Interactions between kisspeptin and neurokinin B in the control of GnRH secretion in the female rat

“…The patterns of expression of NKB and NK3R we observed in sections through the central forebrain corroborate previous studies, documenting their widespread distribution and notable regional concentrations (10). Although the functional significance of NKB/NK3R signaling in reproductive physiology is beginning to emerge (34,36,38), its relevance to other brain functions remains largely a mystery.…”

Goldfish neurokinin B: Cloning, tissue distribution, and potential role in regulating reproduction

“…Differential expression of Tac2 (TAC3 in human and other vertebrates) in rodents has also been observed. For example, Tac2 was detected in the hippocampus and in the nucleus of the lateral olfactory tract in the rats, but not in mice (Duarte et al, 2006).…”

The evolution of tachykinin/tachykinin receptor (TAC/TACR) in vertebrates and molecular identification of the TAC3/TACR3 system in zebrafish (Danio rerio)

“…Loss-of-function mutations in either TAC3 or TACR3 could lead to hypogonadotrophic hypogonadism in human, indicating that the NKB/NK 3 system is indispensable for the human reproductive axis (Topaloglu et al, 2009). Neuroanatomical studies have revealed that NKB neurons are mainly located in the arcuate nucleus, sending their projections to the GnRH terminals in the median eminence where TACR3 is expressed (Abel et al, 1999;Duarte et al, 2006;Foradori et al, 2006;Goodman et al, 2007;Navarro et al, 2009;Pillon et al, 2003;Ramaswamy et al, 2010;Sandoval-Guzmán and Rance, 2004;Wakabayashi et al, 2010). These data suggest that the TAC3/TACR3 system controls reproduction by modulating GnRH secretion.…”