Expression of zebrafish tac3a, tac3b, tac3ra, or tac3rb mRNA in various parts of the brain (A) and changes in zebrafish tac3a at various ages toward puberty (B) as determined by real-time PCR. The relative abundance of the mRNAs was normalized to the amount of elongation factor 1 α (ef1α) by the comparative threshold cycle method; the comparative threshold reflects the relative amount of the transcript. Results are means ± SEM (n = 11-15). Means marked with different letters differ significantly (P < 0.05).

(A-O) Localization of tac3a during early stages of development, as detected by whole-mount ISH. tac3a is dominantly expressed in the right habenular nuclei, midbrain, and hindbrain. Dorsal view of larva heads, anterior is to the left (A-E). High magnification of boxed area in Upper panel. Note the unilateral expression of tac3a to right of the midline (dotted line) in the habenula (F-J), lateral view of larva heads (K-O). rHbn, right habenula; MB, midbrain; HB, hindbrain. (P-R) Localization of tac3a in adult zebrafish brain as indicated by ISH (nomenclature according to ref. 40). Tac3a mRNA-expressing cells were observed in the ventral (Hav) and medial (Ham) habenula (P) tac3a mRNA-expressing cells detected in the periventricular nucleus of posterior tuberculum (TPp), dorsal (Hd), and ventral zone (Hv) of periventricular hypothalamus (Q) tac3a mRNA-expressing cells observed in the posterior tuberal nucleus (PTN) and central zone (Hc) of periventricular hypothalamus (R). (Magnification: A-E and K-O, 40×; F-J, 120×).

Exposure to estradiol (18 nM) by immersion caused a significant increase in mRNA expression of ligands (A) or receptor (B) genes, in the brain of juvenile zebrafish. sGnRHa, zfNKBa, zfNKBb, zfNKF, or senktide (see legend to Fig. 4 for details), were injected intraperitoneally to mature zebrafish and blood was collected 6 h thereafter (C). Hormone values are means ± SEM. Statistical significance vs. corresponding control values: **P < 0.01; *P < 0.05.

Localization by real-time PCR of zebrafish tac3a, tac3b, tac3ra, and tac3rb mRNA in various tissues. The relative abundances of the mRNAs were normalized to the amount of elongation factor 1-α (ef1α) by the comparative threshold cycle method, where the comparative threshold reflects the relative amount of the transcript. Ant. Intest+ panc., anterior intestine and pancreas; post. Intes, posterior intestine. We found low levels of mRNA expression of all four transcripts in the liver, retina, and adipose tissue. However, relatively high mRNA levels of tac3a and tac3rb were expressed in the gills, tac3a in the posterior intestine and tac3ra in the muscle.