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. 2008 Oct 28;6(10):e254. doi: 10.1371/journal.pbio.0060254

Figure 3. Somatotropic Signals in the Hypothalamic-Pituitary Complex.

Figure 3

(A) Efficient Cre-lox recombination in hypothalamus, not in pituitary, as shown by X-Gal-staining of a sagittal NesCre +/0 ;Rosa26R +/0 brain section: the anterior pituitary originates from the pharyngeal wall, not from neuroepithelium, to which NesCre transgene expression is confined. Abbreviations: 3V, third ventricle; aP, anterior pituitary; Bo, bone; Hpt, hypothalamus; Inf, infundibulum; iP, intermediate pituitary; ME, median eminence; pP, posterior pituitary; R, recessus of the third ventricle. PCR analysis of genomic DNA confirmed absence of recombination from the pituitary: intact Igf1r flox alleles in pituitary, and knockout (Igf1r −) alleles prevalent in hypothalamus.

(B) GHRH immunoreactivity (red) at nerve endings in the ME was weaker than control in bIGF1RKO+/− mice (65 ± 6 versus 122 ± 10 au (arbitrary units), p < 0.01, n = 3), whereas SRIH (green) was unaffected (191 ± 3 versus 197 ± 5 au, n = 3). Briefly, ME tissue sections from the same anatomical location in three bIGF1RKO+/− and three control 10-day-old males were subjected to IHC. Micrographs were taken under identical conditions. For each animal, data from ten sections were averaged. The ratio of GHRH to SRIH immunoreactivity was lower in bIGF1RKO+/− than in control animals (0.34 ± 0.05 versus 0.54 ± 0.09, n = 6; p = 0.06).

(C) Similarly, GHRH gene expression (measured by quantitative real-time RT-PCR, relative to β-actin) was lower at age 10 d in mutants than controls.

(D) SRIH expression was similar in mutants and controls.

(E) Pit-1 expression (relative to 18S rRNA) was lower in bIGF1RKO +/− than wild-type pituitaries at age 10 d.