Intracerebroventricularly Administered Oxytocin Attenuated Cortisol Secretion, but not Behavioral Responses, during Isolation in Holstein Steers

Abstract

ABSTRACT. In rodents, intracerebroventricular oxytocin administration attenuated hypothalamo-pituitary-adrenal (HPA) responses and anxiety behavior during stress. We examined the effects of intracerebroventricular injection of oxytocin on isolation-induced stress responses in cattle. In a methodological test, we determined the dosage of oxytocin applied in a main test which did not induce an increase in plasma cortisol concentration or stereotyped behaviors. In a main test, 5 steers aged from 199 to 250 days were assigned to the following three treatments randomly: T1, no isolation after injection of 200 µl of artificial cerebrospinal fluid (aCSF); T2, isolation after aCSF injection; and T3, isolation after 0.5 µg of oxytocin in 200 µl aCSF injection. The isolation was conducted by leaving the experimental steer alone in its stall for one hour while its peers were taken outside. In T2, the isolation induced a rapid increase in plasma cortisol concentration. The maximum %-changes from the pre-isolation value were significantly attenuated by oxytocin injection (T2 vs. T3, p<0.05). The isolation also induced an increase in the frequency (number of occurrences/1 hr isolation) of vocalizations and body orientation changes, and a decrease in the percentage of time spent lying and ruminating. The effect of oxytocin on these behavioral responses to isolation was not apparent. These results indicate that intracerebroventricularly injected oxytocin at low dose attenuated the cortisol response to isolation in steers while the effect on behavior was very small in this experimental condition. KEY WORDS: behavior, cortisol, isolation, oxytocin, steer.J. Vet. Med. Sci. 70 (7): [665][666][667][668][669][670][671] 2008 In response to various stressors, oxytocin is released not only peripherally, but also intracerebrally to regulate pituitary-adrenocortical and behavioral stress responses [11]. Recent studies in rodents have shown that oxytocin suppresses the hypothalamo-pituitary-adrenal (HPA) response to stressors [11,12,18] and has anxiolytic properties [9,19]. There are, however, few studies about the anti-stress effect of central oxytocin in animals other than rodents. In sheep, oxytocin infusions directly into the posterior pituitary, but not into paraventricular nucleus of the hypothalamus, suppressed cortisol responsiveness to an acute psychological stressor, a barking dog [4]. They, however, did not elucidate the anxiolytic properties of oxytocin because of their experimental design.Recently, Ludwig et al. reviewed evidence that neuropeptides, such as oxytocin and vasopressin, are released from dendrites and diffuse to distant targets to exert long-lasting changes on behavior [8]. We tried to mimic this phenomenon by intracerebroventricular administration of oxytocin.We used steers in the present study. The anti-stress effect of central oxytocin has not been elucidated in cattle. In our previous study in steers, intracerebroventricularly infused corticotropin-releasing hormone (CRH) or arginine vasopressin (AVP) activ...

Effects of Intracerebroventricularly Administered Carbetocin on Social Behavior in Holstein Steers

“…In steers, intracerebroventricular administration of a comparable molecular dose of OXT (50 μg: 49.6 nmol) activated the hypothalamo-pituitaryadrenal axis and induced stereotypical behaviors [27]. Because the closely related nonapeptide, arginine vasopressin (AVP), induced stress-like responses in steers [28], we had speculated that an excessive amount of OXT would stimulate AVP V1b receptors [27].…”

“…In steers, intracerebroventricular administration of a comparable molecular dose of OXT (50 μg: 49.6 nmol) activated the hypothalamo-pituitaryadrenal axis and induced stereotypical behaviors [27]. Because the closely related nonapeptide, arginine vasopressin (AVP), induced stress-like responses in steers [28], we had speculated that an excessive amount of OXT would stimulate AVP V1b receptors [27]. Schlosser et al also reported that the OXT-elicited increase in adrenocorticotropic hormone release is mediated via AVP V1b receptors in rats, whereas OXT affinity for the V1b receptor is one order of magnitude less than AVP [20,23].…”

“…The half-life of OXT itself, however, is less than 20 min in cerebrospinal fluid [18]. Moreover, high doses of intracerebroventricularly administered OXT have been shown to induce stress-like responses, such as an increase in plasma cortisol (CORT) concentration and abnormal stereotypical behavior, in steers [27].Deamino-1-monocarba-(2-O-methyltyrosine)-oxytocin (carbetocin; CBT), an OXT analog, has been synthesized to be protected from aminopeptidase and disulfidase cleavage and has prolonged uterotonic activity [2,5,8]. Both the peripheral and central administration of CBT induces anxiolytic-like behavioral effects through OXT receptor activation [3,[11][12][13]15]; unlike OXT, these effects are dose-dependent and last longer [5,12,13].…”

“…The half-life of OXT itself, however, is less than 20 min in cerebrospinal fluid [18]. Moreover, high doses of intracerebroventricularly administered OXT have been shown to induce stress-like responses, such as an increase in plasma cortisol (CORT) concentration and abnormal stereotypical behavior, in steers [27].…”

Role of oxytocin in improving the welfare of farm animals — A review

“…It was reported that intranasal OT administration attenuated the adreno-cortico-tropic-hormone. response in monkeys [35], and centrally administered OT attenuated cortisol secretion in Holstein steers [36]. Further, intranasal OT injection had an anxiolytic-like effect on rats [37,38].…”