Four prepubertal pigs were prepared with venous catheters and housed in metabolism cages. Plasma and saliva samples were taken at 15-min intervals over a 105-min period and analysed by radioimmunoassay for total (i.e. free and bound) cortisol content. Adrenocorticotrophic hormone (ACTH) was given i.v. at three different doses (0.5, 1.0 and 2.0 mg) after the second sample and the cortisol responses were compared with pretreatment values and levels observed after saline vehicle administration. Basal levels of salivary cortisol were approximately 10% of those in plasma. ACTH induced significant increases in plasma and salivary cortisol but in no case was a dose/response relationship detected. Plasma cortisol showed a maximum increase of approximately 230% whereas salivary cortisol increased only by about 130%, indicating that salivary cortisol is a less sensitive indicator of adrenal activity than plasma cortisol in this species. Estimation of salivary cortisol concentrations may offer practical advantages for the assessment of stress responses in intensively housed pigs.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

Changes in pig salivary cortisol in response to transport simulation, food and water deprivation, and mixing.

Cortisol concentrations in the saliva of two groups (N = 5/group) of prepubertal pigs were measured by radioimmunoassay. Samples were collected in the home pen under normal husbandry conditions and after a 24 h period when food and water were withheld. The pigs were then transferred to a transport simulator, which was left stationary (control) or set in motion (experimental), and further samples were taken 1 h later before the animals returned to their pens. In the following week, the two groups of pigs were mixed and saliva was collected over a 3 h period. Samples were also taken 2 days later after the pigs had been injected with a maximally stimulating dose of adrenocorticotrophin (ACTH). Transport simulation in deprived animals, and mixing, produced salivary cortisol levels similar to those seen after ACTH. Food and water deprivation alone also increased cortisol secretion whereas transport simulation in non-deprived animals had no effect. These results indicate that salivary cortisol estimation offers a non-invasive means of measuring stress responses in unrestrained pigs.

Animals↗

PubMedDate not supplied

Centrally administered atriopeptin III reduces water intake and vasopressin secretion in dehydrated sheep.

Two experiments were carried out to investigate the responses of sheep (N = 6) to intracerebroventricular (ICV) injections of atriopeptin III [atrial natriuretic factor (5-28), AP III]. In Experiment, 1, 24-h dehydrated animals were given 0 (saline vehicle control), 10 or 30 micrograms AP III directly before the presentation of water. The highest dose of AP III significantly (p less than 0.02) reduced the amount of water drunk in the subsequent 20 min. In Experiment 2, blood samples were taken at various intervals before and after ICV injection of 0 or 30 micrograms AP III when the sheep were water replete or 24-h dehydrated. Plasma concentrations of vasopressin (AVP) and cortisol were measured and estimates were made of plasma osmolality. In the dehydration condition, AVP levels were somewhat reduced (p less than 0.059) after AP III administration but no decrease was observed when the animals were euhydrated. No significant changes in plasma osmolality or cortisol concentrations were observed in response to AP III or the saline vehicle. Because a large dose of AP III (30 micrograms ICV) was required to produce the comparatively small behavioral and endocrine effects observed in this study, the results are suggestive of a pharmacological, rather than a physiological, action of the peptide in this species.

Animals↗

PubMedDate not supplied

Stress-induced changes in c-fos immunoreactivity in the porcine brain.

An immunocytochemical method was used to examine expression of c-fos protein in forebrain and brainstem regions of prepubertal pigs (n = 2 per treatment) subjected to various physical stressors (snaring, cold exposure and transport simulation) and of an untreated animal. Each of the stress procedures induced specific nuclear labelling of neurons in the hypothalamus (paraventricular and especially supraoptic nuclei) and small amounts of labelling in some brainstem regions. These results confirm and extend findings obtained in rodents and indicate the potential value of this technique for stress and welfare research in ungulates.

Animals↗

PubMedDate not supplied

Effects of testosterone on fever and vasopressin mRNA in wether sheep given endotoxin.

This study investigated the effects of testosterone on the febrile response of castrated rams to immunological challenge. Core temperature was recorded by radiotelemetry in wethers (n = 6) injected with lipopolysaccharide endotoxin or saline before and after androgen treatment. The number of cells expressing vasopressin mRNA in the brain region implicated in the anti-pyretic response, the bed nucleus of the stria terminalis, was determined by in situ hybridisation histochemistry. Endotoxin, but not androgen, increased vasopressin message (P < 0.05), and androgen also did not alter basal or febrile temperatures. Hence, these preliminary findings question whether the androgen-dependent anti-pyretic mechanism described in the male rat is of physiological significance in the ram.

Animals↗

PubMedDate not supplied

Effects of transport and indomethacin on telemetered body temperature and release of cortisol and prolactin in pre-pubertal pigs.

Previous research indicates that acute physical stress (restraint) raises core temperature in growing pigs via a prostaglandin-dependent mechanism. This study investigated whether transport stress affects body temperature in pigs and whether any such changes might involve endogenous prostaglandins. Pre-pubertal boars (n = 7) were implanted with venous catheters and biotelemetry devices for the measurement of core temperature. They were transported for two hours, with and without indomethacin (IND) pre-treatment, and blood samples were taken at 15 minute intervals for the determination of plasma cortisol and prolactin concentrations. The results indicated that, contrary to predictions, body temperature tended to fall during transport and that the effect was exaggerated by IND. By contrast, cortisol concentrations increased during transport and were unaffected by IND whereas the tendency for transport to stimulate prolactin release was reversed by IND.

Analysis of Variance↗

PubMedDate not supplied

Hippocampal gene expression in the pig: upregulation of corticotrophin releasing hormone mRNA following central administration of the peptide.

Corticotrophin releasing hormone (CRH) and glucocorticoids affect hypophysiotrophic regions of the brain and influence limbic system activity. Since the latter mediates emotional responses, changes in gene expression in regions such as the hippocampus may provide new information on neural stress mechanisms. In this study, mRNA for CRH and selected ionotropic glutamate receptor (iGluR) subunits (NR1, GluR2, GluR3) was quantified in the hippocampus of pigs in which stress was simulated by central administration of CRH (100 microg). Increases in hippocampal CRH mRNA were detected in the CA3 subfield 4 h later, and in the CA1, CA2 and CA3 subfields 24 h post-treatment. However, there were no associated changes in iGluR subunit mRNAs, although the ratio GluR3: GluR2 increased in the dentate gyrus after 4 h. These results, together with a recent similar finding in rats subjected to restraint, point to an involvement of hippocampal CRH in the neuronal response to stress.

Animals↗