Serotonergic and catecholaminergic interactions with co-localized dopamine-melatonin neurons in the hypothalamic premammillary nucleus of the female turkey during different reproductive states
S.W. Kang, B. Leclerc, L.J. Mauro, and M.E. El Halawani
University of Minnesota, St. Paul
Serotonin (5-HT) and catecholamines (CAs; epinephrine and norepinephrine) appear to have important roles as neurotransmitters in avian reproduction, but their neuroanatomical relationship to the neuroendocrine circuitry that regulates reproduction is poorly understood. Our previous studies lead to the hypothesis that 5-HTergic/CAergic neurons in the brainstem and their interaction with PMM DA-MEL neurons might be an important circuit for reproductive function in the female turkey. The retrograde fluorescent tract tracer, DiI was injected into the PMM, and combined with 5-HT, tyrosine hydroxylase (TH), dopamine β-hydroxylase (DBH), and phenyl N-methyltransferse (PNMT) immunocytochemistry (ICC) to reveal neuroanatomical connections. Changes in the activities of 5-HTergic, and CAergic neuronal systems projecting to the PMM were measured at different reproductive states with in situ hybridization technique, using tryptophan hydroxylase 2 (TPH2) and TH mRNA expression, respectively. Cells labeled with DiI were found in anatomically discrete areas in or near the hypothalamus and the brainstem. Double ICC, using TH/5-HT, TH/DBH and TH/PNMT antibodies, confirmed that there were 5-HT, DBH, and PNMT immunoreactive fibers in close approximation to DA-MEL neurons. TPH2 mRNA expression in 5-HT neurons was found in the AVT, nDBC, LC, LoC, SCv and R. ABSTRACTS OF PAPERS 15 TPH2 mRNA expression level was greatest in laying and incubating hens and least in the sexually inactive short day and photorefractory hens in all areas, except in the R. The most abundant expression of TPH2 mRNA was seen in the LoC of laying and incubating hens. Among the CAergic areas labeled with Dil, the nTS showed the highest level of TH mRNA expression in photorefractory hens and the lowest level in incubating hens. The patterns of 5-HT/CA neuronal distribution and their variable interactions with PMM DA-MEL neurons during different reproductive states may offer a significant neuroanatomical basis for understanding the control of avian reproduction. USDA Grant No. 2007-35203-18072.
Circadian expression of clock genes in the pineal gland, visual suprachiasmatic nucleus (vSCN) and premammillary nucleus (PMM) in photostimulated turkey hens
B. Leclerc, S. Kang, C. Howell, L. Mauro, and M.E. El Halawani
University of Minnesota, St. Paul
Dopamine-melatonin (DA-MEL) neurons in the PMM have previously been described to be light/dark-inducible at 14 hours after light on during the photosensitive phase. It is hypothesized that these PMM DA-MEL neurons may be a component of a biological clock involved in the reception of photoperiodic information critical for the regulation of seasonal reproduction in turkeys. To establish whether clock and melanopsin genes rhythms are related to the activation of these neurons, night interruption studies and circadian expression profile of these genes were conducted. In the first experiment, short day (6L:18D) birds were subjected to a light pulse of 30, 60 and 180 minutes duration at circadian times (CT) 8, 14, and 20. In the second experiment, short (8L:16D) and long day (16L:8D) birds were both sampled at CT1, CT5, CT9, CT13, CT17 and CT21. Brains were collected from each bird, the PMM and the vSCN were isolated using micropuncture technique and total RNA was extracted from nuclei and pineal glands. RT-PCR analysis was performed to determine the fold change in bmal1, clock, cry1, cry2, per2, per3, and melanopsin mRNA transcripts. In the night interruption study, our results suggest that 1 hour light stimulation induced (P<0.05) per3 gene expression in the pineal and PMM, but repressed it (P<0.05) in the vSCN. A similar trend was observed for bmal1 and cry1 genes in the vSCN and PMM. In the circadian profile study, pineal cry1 gene reached a nadir at CT21 and peaked at CT13 in the PMM, whereas melanopsin gene reached a zenith at CT21 and nadir at CT13 in the respective tissues. In the PMM, per2 gene peaked at CT5, whereas per3 gene was repressed at CT9. In the pineal and vSCN, both genes were positively related at CT1 and CT9-13, respectively. This study suggests that light is an effective entrainer of clock genes which are differently expressed in these neuronal targets. Supported by National Research Initiative Grant (2007-35203-18072) from the USDA Cooperative State Research, Education, and Extension Service.
Response of market turkey toms to diets containing high levels of corn distillers dried grains with solubles
S.L. Noll and J. Brannon
University of Minnesota, St. Paul
The response of market turkey toms to corn distillers dried grains with solubles (DDGS) was examined during 2-19 wk of age. Large White male turkey poults (Nicholas strain) were randomly assigned to pens (10/pen) at 2 wk age and fed one of the following diet treatments (T): 1) Corn-soy control, no DDGS; 2) same as T1 with 10% DDGS; 3) same as T1 with 20% DDGS; 4) same as T1 with 30% DDGS; 5) same as T2 starting at 5 wk of age; 6) same as T3 starting at 5 wk of age; 7) same as T4 starting at 5 wk of age; 8) same as T1 with 5% DDGS increasing to 20% DDGS at 8 wk of age; 9) same as T1 with 5% DDGS increasing to 30% DDGS at 11 wk of age; and 10) same as T1 with 5% DDGS increasing to 40% DDGS at 11 wk of age. Diets were formulated to contain 100% NRC digestible Thr primarily from intact protein although some supplemental Thr was used in the starter and grower diets. The basal diet was composed primarily of corn, soybean meal, and poultry by-product meal. Diets were formulated using digestible amino acids. All diets were supplemented as needed with Lys and met to meet the specific NRC recommendations for these amino acids. Diet levels of poultry by-product meal were limited to prevent an excess of dietary phosphorus. Each diet was fed to 9 replicate pens. The experimental design was a completely randomized block design. Dietary treatment affected body weight at 19 wk (P<0.06), where the BW of T10 was 2.9% less than that of T1. Difference in average daily gain from that of the control (T1) was observed only during 17-19 wk of age for T10 with depressed gain, in agreement with the observed reduction in BW at 19 wk but not at 17 wk of age. Feed efficiency differed from T1 during 2-19 wk of age with poorer feed:gain for T6, T8, and T9. The results indicate that feeding levels of up to 30% DDGS in turkey starter diets was not detrimental to poult weight or feed efficiency. In turkey finisher diets, feeding of up to 40% DDGS was not detrimental to growth until 17 wk of age. High inclusion levels of DDGS had inconsistent effects on feed efficiency.
Changes in vasoactive intestinal peptide immunoreactivity in the brain of nest-deprived native Thai hens
N. Prakobsaeng1, N. Sartsoongnoen1, S. Kosonsiriluk1, T. Songserm2, I. Rozenboim3, M.E. El Halawani4, and Y. Chaiseha1
Like Gallinacous-temperate zone birds, hyperprolactinemia has been associated with incubation behavior and ovarian regression in the native Thai chicken, a tropical nonseasonally breeding avian species. The objective of this study was to compare the changes in the number of vasoactive intestinal peptide-immunoreactive (VIP-ir) neurons in the nucleus infundibuli hypothalami (IN) and nucleus inferioris hypothalami (IH) of incubating native Thai hens (B; n=4) with those of nest-deprived hens (NB; n=4). Blood samples were collected for determining prolactin (PRL) levels by Enzyme-Linked ImmunoSorbent Assay. The results revealed that the number of VIP-ir neurons in the IN-IH of incubating hens on days 6 (B6), 10 (B10), and 18 (B18) of incubation were 128.5 ± 13.0, 138.4 ± 13.0, 100.8 ± 7.3 cells, respectively. When the hens were nest deprived, the number of VIP-ir neurons markedly decreased (P<0.05) to that the same level of laying hens (NB6 = 82.4 ± 11.2; NB10 = 53.9 ± 6.6; NB18 = 40.3 ± 5.7 cells). In addition, this disruption of broodiness was accompanied by a precipitous decline in circulating PRL. The PRL levels (ng/mL) were significantly decreased after nest depriving the hens (B6 vs. NB6; 329.8 ± 18.6 vs. 34.1 ± 6.6, B10 vs. NB10; 481.5 ± 40.1 vs. 15.4 ± 1.4, B18 vs. NB18; 101.1 ± 41.8 vs. 24.8 ± 3.8). This study indicates an association between VIP neurons in the IN-IH and the degree of hyperprolactinemia, suggesting that the differential expression of VIP neurons in the IN-IH might play a regulatory role in year-round reproductive activity and subsequent PRL release in such birds. Supported by The Thailand Research Fund: no. RSA4780001 (YC) and no. PHD/0176/2547 (YC/NP).
1School of Biology, Suranaree University of Technology, Thailand
2Department of Pathology, Kasetsart University, Thailand
3Department of Animal Science, The Hebrew University of Jerusalem, Israel
4Department of Animal Science, University of Minnesota, St. Paul
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