Animal Science Journal (2003) 74, 37–44 37 Blackwell Science, LtdOxford, UK ASJAnimal Science Journal1344-39412003 Blackwell Science Asia Pty Ltd 741February 2003 084 Infusions of corticotropin-releasing hormone in sheep K. YAYOU et al. 10.1046/j.1344-3941.2002.00084.x Original ArticleBEES SGML Correspondence: Ken-ichi Yayou, National Agricultural Research Center for Hokkaido Region, 1, Hitsujigaoka, Toyohira-ku, Sapporo-shi, 062–8555, Japan. (Email: ken318@affrc.go.jp) Received 15 May 2002; accepted for publication 4 September 2002. ORIGINAL ARTICLE Effects of intracerebroventricular infusions of corticotropin-releasing hormone in sheep Ken-ichi YAYOU, 1 Humihiro OTANI, 2 Naozumi TAKUSARI, 2 Katsuji UETAKE 3 and Takashi OKAMOTO 2 1 National Agricultural Research Center for Hokkaido Region, Toyohira-ku, Sapporo-shi, 2 National Institute of Livestock and Grassland Science, Tsukuba Norin Kenkyu Danchi, Ibaraki-ken and 3 Department of Veterinary Medicine, Azabu University, Sagamihara-shi, Japan ABSTRACT To provide new insights into the neural mechanisms of physiological and behavioral responses to stressors in sheep, acute changes in endocrine, autonomic and behavioral functions following 30 min infusions of ovine-corticotropin-releasing hormone (oCRH; 0, 0.5, 5 or 50 mg/0.5 mL of artificial cerebrospinal fluid/30 min) into the third ventricle of sheep (n = 7– 8) were examined. Serial blood samples were collected through indwelling jugular catheters to determine plasma cortisol concentrations (CORT). Heart rate (HR) and rectal temperature (RT) were obtained via telemetry systems. The behaviors of the animal were monitored simultaneously. Intracerebroventricular infusions of CRH dose-dependently induced an increase in CORT; there was a time–treatment interaction in CORT (P < 0.001). There was not a time–treatment interaction either in HR (P = 0.29) or in RT (P = 0.28). That RT showed a tendency to decrease with higher doses of CRH in sheep was in contradiction to previous reports in rats and pigs. As to changes in behavioral function, only the induction of bleating was marked. These results suggest that in physiological and behavioral responses of sheep to stressors, CRH regulates the increase in CORT and the induction of bleating. However, CRH might have little function in sympathetic nervous activation during physiological responses to stressors in sheep. KEYWORDS: bleating, corticotropin-releasing hormone, cortisol, rectal temperature, sheep. INTRODUCTION Quantitative analysis of stress in farm animals is essen- tial to evaluate animal well-being (Brambell 1965). Various evaluative approaches have been attempted by monitoring, for example: changes in behavioral function such as suppression of the normal behavioral repertoire and occurrence of conflict and/or abnormal behavior; endocrine function such as changes in plasma concentrations of adrenocorticotropic hor- mone (ACTH) and cortisol; and autonomic nervous function such as heart rate and body temperature. There are, however, several discrepancies among such indicators depending on the type and the intensity of the stressor and the individual that makes the quan- titative analysis of stress confusing. Since the discovery of corticotropin-releasing hor- mone (CRH) by Vale et al. (1981), much evidence has suggested that CRH plays an important role in medi- ating the stress responses listed above. In rodents, activation of locomotor activity, hypothalamic- pituitary-adrenal axis, and sympathetic nervous activ- ity were simultaneously observed in an integrated fashion after central injection of CRH (Diamant & De Wied 1991; Morimoto et al. 1993). In farm animal