Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias

16 t h International Congress on Animal Reproduction
144 Poster Abstracts
immunohistochemistry. Exposure to ewes stimulated an increase in
LH pulse frequency (0.19 ± 0.12 vs. 0.75 ± 0.14 pulses/h; P < 0.01),
mean concentration of LH (0.16 ± 0.06 vs. 0.53 ± 0.21 ng/mL; P <
0.05) and basal concentration of LH (0.08 ± 0.01 vs. 0.13 ± 0.01
ng/mL; P < 0.05). Exposure did not affect LH pulse amplitude (0.55 ±
0.15 vs. 0.55 ± 0.15 ng/mL; P > 0.1). In Control rams, there was no
change (P > 0.1) in LH pulse frequency (0.25 ± 0.10 vs. 0.25 ± 0.10
pulses/h), mean concentration of LH (0.15 ± 0.03 vs. 0.11± 0.01
ng/mL), basal concentration of LH (0.08 ± 0.02 vs. 0.12 ± 0.02
ng/mL) or LH pulse amplitude (0.62 ± 0.09 vs. 0.70 ± 0.09 ng/mL).
Preliminary analysis of the histology indicates that Ewe-exposed rams
have a greater number of Fos-immunoreactive cells in the
ventromedial hypothalamus, and probably other regions, than Control
rams. This result corresponds with studies in the ewe that have
identified neural activation in the ventromedial hypothalamus of ewes
following stimulation by rams (1). 1. Gelez H, Fabre-Nys C. Neural
pathways involved in the endocrine response of anestrous ewes to the
male or its odor. Neuroscience 2006;140: 791-800. 2. Rosa HJD,
Bryant MJ. The 'ram effect' as a way of modifying the reproductive
activity in the ewe. Small Ruminant Research 2002;45: 1-16.
P354
Plasmatic thyroxine and triiodothyronine concentrations
in non-pregnant, pregnant and lactating Saanen breed
goats
Greco, G 1 *; Baldini, L 1 ; De Paula, M 1 ; Bittencourt, RF 1 ; Maia, L 2 ; Oba, E 1
1Department of Animal Radiology and Reproduction, São Paulo State
University -UNESP - Botucatu, Brazil; 2 Department of Veterinary Clinics and
Pathology, Fluminense Federal University -UFF, Brazil
Thyroid hormone receptors are expressed in most of the animal
tissues, being responsible for activating biochemical reactions and
organic responses. In pregnant goats, these hormones are essential for
normal fetal development and organogenesis and, during the
lactational period, they stimulate galactopoiesis. As in sheep, thyroid
hormones seem to be involved regulating reproductive sazonality in
the caprine species. In comparison to other ruminants, few studies
have been published regarding the variations in the concentrations of
thyroxine (T4) and triiodothyronine (T3) in goats, according to their
reproductive state. The present work had as objective to determine the
plasmatic concentrations of T3 and T4 in non-pregnant, pregnant and
lactating Saanen breed goats. Forty-three female Saanen goats, aging
24 to 32 months, were assigned into three different groups. Group 1
was composed of 15 non-pregnant goats. Thirteen goats experiencing
their last month of pregnancy were assigned to group 2. As for group
3, it was composed of 15 lactating goats, whose kids were at most one
month old. Blood was collected from animals through jugular
venipuncture into tubes containing heparin, which were centrifugated
at 3000 x g for 15 minutes. Plasma obtained was stored at – 20
degrees Celsius. T3 and T4 concentrations were estimated through
radioimmunoassay, using Diagnostic Products Corporation® (DPC)
kits. The obtained data was statistically analyzed through the
Statistical Analysis System®, version 6.1, 1996. Concentrations of T3
and T4 were compared between the groups using the Student-
Newman-Keuls test. The correlation between T3 and T4 measured
concentrations was established using the PROC CORR procedure.
Significance levels were set as P < 0.05. A highly significant (P <
0.01) positive correlation was found between T3 and T4 overall
concentrations. Mean T3 concentrations were 150.08 ng/dL +/- 46.7,
108.48 ng/dL +/- 41.1 and 171.55 ng/dL +/- 38.3 in groups 1, 2 and 3,
respectively. Pregnant goats had lower (P < 0.05) T3 concentrations
than lactating and non-pregnant animals. As for T4, mean
concentrations were, respectively, 5.40 μg/dL +/- 1.38, 3.76 μg/dL +/-
1.05 and 6.51 μg/dL +/- 1.43 in groups 1, 2 and 3. Lactating goats had
higher (P < 0.05) T4 concentrations than non-pregnant animals. T4
concentrations obtained from pregnant goats were significantly lower
(P < 0.05) than those in the remaining groups. In conclusion, T3 and
T4 concentrations are lower in pregnant Saanen goats, being the
concentration of T4 higher during the lactational period.
P355
Salsolinol as a hypothalamic neurotransmitter stimulating
prolactin release during suckling in ewes
Misztal, T 1 *; Gorski, K 1 ; Tomaszewska-Zaremba, D 2 ; Molik, E 3 ; Romanowicz,
K 1
1Department of Endocrinology, 2 Department of Neuroendocrinology, The
Kielanowski Institute of Animal Physiology and Nutrition in Jablonna, Poland;
3Department of Sheep and Goat Breeding, Agricultural University in Cracow,
Poland
Introduction Salsolinol is a dopamine-derived, endogenously
synthesized compound associated mainly with dysfunction of
dopaminergic neurons. Recent data suggest, however, that salsolinol
may also be involved in the dopaminergic regulation of prolactin
secretion. It has been shown that in rats, the brain salsolinol
concentration is elevated during situations when pituitary prolactin
secretion is increased. In the present study, we hypothesized that
salsolinol was present in the infundibular nucleus-median eminence
(IN/ME) of lactating ewes and that its extracellular concentration in
the IN/ME increased in response to suckling, similarly to the plasma
prolactin concentration. The second hypothesis was that exogenous
salsolinol, infused into the third ventricle (IIIv) of the brain, could
stimulate prolactin secretion in lactating ewes.
Material and Methods Stainless steel guide canullae were implanted
under stereotaxic control into the IN/ME (n=6) or into the IIIv (n=10)
through a drill hole in the skull in the second moth of pregnancy and
two experiments were performed during the fifth week of lactation. 1)
Perfusions of the IN/ME with Ringer-Locke solution were performed
in ewes bilaterally, from 10:00 h to 15:00 h, by the push-pull method
and were divided to the non-suckling and suckling periods, both for
2.5 h. At least 9 or 10 perfusates were collected during perfusion. 2)
Pulsatile infusions of salsolinol (5 x 1 μg/20 μl, n=5) or vehicle (n=5)
into the IIIv were performed from 12:30 h to 15:00 h, corresponding
to the suckling period in perfused ewes. The preinfusion period was
from 10:00 h to 12:30 h. In both experiments, plasma samples were
collected every 10 minutes, through a catheter inserted into the jugular
vein. The perfusate concentration of salsolinol and plasma
concentration of prolactin were assayed by HPLC and RIA,
respectively.
Results The presence of salsolinol, but not dopamine, was detected in
the perfusates collected from the IN/ME of lactating ewes. Perfusate
salsolinol concentrations during the non-suckling period vs. suckling
period were 56.82 ± 13.78 vs. 150.08 ± 16.85 pg/50 μl (mean ± SEM,
P