Regional brain neurotransmitter concentrations in stress-susceptible pigs

In three experiments, the concentrations of indoleamines and catecholamines were measured in the brain regions of pigs that were homozygous-positive (nn, stress-susceptible), heterozygous (Nn), and homozygous-negative (NN, stress-tolerant) for the halothane gene. In Exp. 1 (n = 10), hypothalamic 5-hydroxytryptophan (P < .1) and serotonin (P < .05) were lower in nn than in NN pigs. Concentrations of 5-hydroxytryptophan, serotonin, dihydroxyphenylethylamine (DOPAMINE), norepinephrine, and epinephrine in the hypothalamus and caudate nucleus were lower (P < .05) in nn (n = 8) than in NN (n = 7) pigs in Exp. 2. However, there were no differences in dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) between nn and NN pigs. Hippocampal serotonin and norepinephrine were lower (P < .05) in nn than in NN pigs. In the third experiment, serotonin was the only neurotransmitter that was lower in the hippocampus of Nn (n = 5) than of NN (n = 6) pigs; concentrations of all other neurotransmitters in the three brain regions were similar between Nn and NN pigs. Results from these experiments suggest central nervous system involvement in porcine stress syndrome.