Luteinizing Hormone-Releasing Hormone Gene Expression in the Bovine Brain: Anatomical Localization and Regulation by Ovarian State1

Abstract

Experiments were conducted to identify neurons in the bovine brain that express the LHRH gene and to determine whether LHRH mRNA levels are influenced by the ovaries. Two groups of postpubertal heifers were utilized: heifers killed during the mid-luteal phase of the estrous cycle (LUTEAL, n = 5) and heifers killed 14-16 wk following ovariectomy (OVX, n = 5). In situ hybridization was performed through use of a 32P-end-labeled deoxyoligonucleotide (59 mer) complementary to the human LHRH mRNA sequence. LHRH-expressing neurons were identified in the diagonal band of Broca, the preoptic area, and the anterior hypothalamus in a manner consistent with immunocytochemical localization. Reduced silver grains, proportional to LHRH mRNA content, were quantified (in pixels, 45x objective) with an image analysis system. Expected serum hormone concentration differences between endocrine states were confirmed by radioimmunoassay for progesterone (LUTEAL > OVX, p < 0.01) and for LH (OVX > LUTEAL, p < 0.01). Compared to the OVX group, LUTEAL heifers had 34% fewer LHRH-expressing neurons (p < 0.05); on the average, these neurons possessed 28% fewer pixels/cell (p < 0.01), indicating fewer copies of LHRH mRNA per cell. When the numbers of pixels in all labeled cells were totalled, LUTEAL animals had 57% fewer pixels (p < 0.05) than did the OVX females--probably reflecting a decrease in LHRH synthetic capacity in the LUTEAL animals. Therefore, during the mid-luteal phase of the bovine estrous cycle, ovarian steroid (i.e., luteal progesterone) suppression of LHRH release (as reflected by serum LH) is coincident with decreased LHRH mRNA in the brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Exogenous Recombinant Ovine Interferon Tau on Circulating Concentrations of Progesterone, Cortisol, Luteinizing Hormone, and Antiviral Activity; Interestrous Interval; Rectal Temperature; and Uterine Response to Oxytocin in Cyclic Ewes1

“…Twenty cyclic ewes received s.c. injections of either 0 (same volume of vehicle), 2, 4, or 6 mg roIFNr on the morning of Day 12. Concentrations of LH in plasma were determined by RIA as described by Weesner et al [18] with the modification that NIAMDD-ovine LH-24 was used as the reference standard. In addition, blood was collected by jugular venipuncture into both EDTA-containing Vacutainer tubes, and Vacutainer tubes containing no additives, at 15-min intervals from -30 min to 3 h and then every 30 min to 6 h and at 12 and 24 h. Plasma (25 pl) was assayed in duplicate for progesterone using the Active Progesterone RIA according to manufacturer's instructions (Diagnostic Systems Laboratories Inc., Webster, TX).…”

Postpartum ovarian activity and response to progestagen treatment in rustic beef cows (Spanish Retinta) underfed to simulate their typical ranging conditions

“…This was consistent with immxmocytochemical localization studies previously conducted with cattle (Dees and McArthur, 1981;Leshin et al, 1988). However, Dees and McArthur (1981) foixnd GnRH la±)elling in the MBH, whereas Leshin et al (1988) did not, and, moreover, Weesner et al (1993) did not find GnRH mRNA labelling in that area. In sheep, 1-2% of the GnRH perikarya were located within the MBH (Lehman et al, 1986) .…”

“…In the above cited study conducted by Weesner et al (1993) with postpubertal heifers, the amount of GnRH mRNA labelling per perikarya and the nimiber of labelled perikarya were lower in the mid-luteal phase of the estrous cycle when compared to ovariectomized females.…”

“…The amount of hypothalamic GnRH mRNA and the systemic mean LH concentrations in postpubertal heifers were lower in cyclic, mid-luteal heifers when compared with ovariectomized heifers (Weesner et al, 1993), suggesting a negative feedback effect of luteal P4 upon the hypothalamo-hypophysial axis.…”

“…The degree of caudal migration of GnRH cells during development depends on the species, although the proportion of these cells found in the more caudal locations (arcuate nucleus in the MBH) is always small, except for humans. With respect to cattle, neurons expressing mRNA for GnRH were labelled at the diagonal band of Broca (rostral hypothalamic boundairy) , POA and the anterior hypothalamus of mid-luteal or ovariectomized postpubertal heifers (Weesner et al, 1993).…”