Urinary and caudate nuclei catecholamine levels in stress-susceptible and normal swine

Eight stress-susceptible and eight normal pigs were used in the first portion of the study. Urine samples were collected for 24 hr over 4 consecutive days while the pigs were kept in metabolism cages. Each 24-hr sample was assayed for epinephrine, norepinephrine and dopamine. Urinary levels of dopamine were lower (P < .01) in the stress-susceptible pigs. No significant differences in urinary epinephrine or norepinephrine were observed. The second portion of the study evaluated the catecholamines in the caudate nucleus of the brain. Six stress-susceptible and six control pigs were examined. Immediately after exsanguination, caudate nuclei were excised and frozen in liquid nitrogen. The caudate nuclei were assayed for catecholamines within 2 to 3 days of freezing. Caudate nuclei dopamine levels were lower (P < .01) in stress-susceptible pigs (5,961 ng/g) than in control pigs (10,878 ng/g). No significant differences in norepinephrine levels of the caudate nuclei were observed between the two groups.