Moslemipur F, Khazali H, Emami meybodi M A. Study of the effects of Neuropeptide Y injections on plasma concentrations of Thyroxine and triiodothyronine in goat . Physiol Pharmacol 2006; 10 (3) :219-227
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http://ppj.phypha.ir/article-1-277-en.html
Abstract: (13680 Views)
Introduction: Neuropeptide Y (NPY) is the most abundant peptide present in mammals'
brains. The majority of NPY-producing neurons is in arcuate and paraventricular nuclei of
hypothalamus which affect hypophysiotrapic factors secretion. In this study we investigated
the effect of intravenous injections of various doses of NPY on thyroxine (T4) and
triiodothyronine (T3) serum concentrations.
Methods: Sixteen adult male sannan goats were assigned to four treatment groups.
Treatments were included daily injections of 0, 10, 20 and 40 μg NPY per kg body weight
named C, L, M and H, respectively. The duration of experiments was 13 consecutive days
divided into three intervals pre-treatment (days 1-3), treatment (days 4-10) and posttreatment
(days 11-14). Blood collections were being done throughout the experiment at
09:00 via jugular vein and injections were in treatment interval via carotid artery at 08:00.
Blood samples were centrifuged and the sera were harvested and used for hormone assay
via radioimmunoassay.
Results: Results showed that treatment H caused 11-fold increase in T4 concentrations and
4-fold increase in T3 concentrations ones versus treatment C (P<0.001). Treatment M also
increased T4 and T3 significantly (P<0.001). The effect of treatment L on T4 concentrations
was significantly incremental (P<0.001) but it has no effect on T3 concentrations (P=0.877).
The stimulatory effect of NPY on thyroid hormones was transient because in post-treatment
interval, T4 and T3 concentrations in treatments L, M and H tended to decline but were yet
significantly higher versus treatment C.
Conclusion: Previous studies in rodents demonstrated inhibitory effect of NPY on
thyroid hormones but in present study completely stimulatory and dose-dependent effects of
NPY on these hormones secretion in goat were observed. thus, we suggest the stimulatory
effect of NPY on thyrotrop axis in ruminants. This discrepancy can be due to different
methodology and difference in neuroendocrine framework controlling thyrotrop axis of
ruminants with rodents.
Key words: Neuropeptide Y, Thyroxine, Triiodothyronine, Radioimmunoassay, Goat