Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 5/20/2003
Publication Date: 6/22/2003
Citation: Barb, C.R., Barrett, J.B., Kraeling, R.R., Matteri, R.L. Orexin-B modulates LH and GH secretion: interaction with the brain-pituitary axis in the pig. Journal of Animal Science. 2003. v. 81(Suppl.1): Abstract p. 101. Interpretive Summary:
Technical Abstract: Two experiments (EXP) were conducted to test the hypothesis that orexin-B affects LH and GH secretion. In EXP I, prepuberal gilts received intracerebroventricular (ICV) injections of 0.9% saline (S; n = 2), 10 ug (n = 2) or 100 ug (n = 2) of orexin-B in S. Blood was collected every 15 min for 2 hr before and 2 hr after ICV injections. In EXP II, anterior pituitary cells from prepuberal gilts were studied in primary culture. On d 4 of culture, 100,000 cells/well were challenged with 0.1, 10 or 1000 nM GnRH; 10, 100 or 1000 nM hGRF-(1-29)NH2 or 0.01, 0.1, 10 or 100 nM , orexin-B individually or in combinations with 0.01 and 1000 nM GnRH or 10 and 1000 nM GRF. Secreted LH and GH were measured at 4 hr after treatment. In EXP I, serum LH and GH concentrations were similar among pigs before treatment and were unaffected by orexin-B treatment; averaging 0.5 ± 0.2, 1.0 ± 0.2 and 1.0 ± 0.2 ng/ml for LH and 2.1 ± 3.4, 6.1 ± 3.4 and 5.8 ± 3.4 ng/ml for GH after ICV injection of S, 10 ug or 100 ug orexin-B, respectively. In EXP II, basal LH and GH secretion (control; n = 9 wells) was 183 ± 18 and 108 ± 4.8 ng/well, respectively. Relative to control at 4 hr, all doses of GnRH and GRF increased (P < 0.001) LH and GH secretion. All doses of orexin-B increased (P < 0.001) GH secretion, while only the 0.010 nM dose increased (P<0.005) LH secretion. Secreted LH and GH were unaffected by addition of 0.01, 0.1, 10 or 100 nM orexin-B in combinations with 0.01 and 1000 nM GnRH or 10 and 1000 nM GRF compared to GnRH or GRF alone, except 0.1 nM orexin-B suppressed (P<0.02) the LH response to 1000 nM GnRH. These results indicate that orexin may directly modulate LH and GH secretion at the level of the pituitary gland, but not the brain.