Effect of isolation stress on beta-endorphin and LH levels in ovariectomized ewes.

Abstract: The objective of this experiment was to study the effect of the psychological stress of isolation on luteinizing hormone (LH) secretion in ovariectomized ewes. Sheep were initially penned in pairs. Isolation was accomplished by removing the non-experimental sheep to another room. The trials lasted from 10.00 untii 18.00 h. ln the first stage (from 10.00 until 14.00 h) the animals were alIowed to have visual contactwith their partners, while in the second stage (14.00 until 18.00 h) the animals were isolated. Blood samples were taken at 15-min intervals throughout the experiment from jugular catheters implanted the previous day. Samples were analysed for glucose, (Betha-endorphin and LH. The isolation stress caused a significant (P < 0.05) elevation of (Betha-endorphin (316 (s.e. 11-4) v. 381 (s.e. 20.7) ng/l) but did not alter significantly (P> 0.05) the mean LH levels (4.23 (s.e. 0.14) v. 3.92 (s.e. 0.13) ug/1). However LH secretion was seen to dec1ine rapidly after the onset of isolation and then to recover. When the data were analysed in 2-h time periods the LH levels were significantly (P < 0.05) reduced betwen the 2 h before (4.70 (s.e. 0.2) ug/l) and after (3.90 (s.e. 0.2) ug/l) isolation. LH pplse analysis performed using PULSAR showed that the pulse frequency and pulse amplitude were reduced after isolation (3.8 (s.e. 1.2) v. 3.3 (s.e. 1.1) pulses per 4 h) and (2.6 (s.e. 1.5) v. 1.6 (s.e. 1.0) ug/I), respectively. Glucose levels showed significant (P < 0.05) elevation (2.7 (s.e. 0.1) v. 3.2 (s.e. 0.1) nmol/1) during isolation stress. We can conclude that a psychological stress such as isolation in a species such as the sheep stimulates opioid peptides release and inhibits LH secretion. Whether these two events are causally linked remains to be clarified.

Bibliographic Details

Main Authors:	ELOY, A. M. X., RODWAY, R. G.
Other Authors:	ANGELA MARIA XAVIER ELOY, CNPC.
Format:	Anais e Proceedings de eventos biblioteca
Language:	English eng
Published:	2011-04-10T11:11:11Z
Subjects:	LH, Endorfina., Ovino, Stress, Hormônio, Sheep, Endorphins.,
Online Access:	http://www.alice.cnptia.embrapa.br/alice/handle/doc/515008
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