P. Mormede et al., INDEPENDENT SEGREGATION OF A HYPERACTIVE HYPOTHALAMIC-HYPOPHYSO-ADRENAL AXIS AND A REDUCED BEHAVIORAL REACTIVITY IN PIGS, Psychoneuroendocrinology, 19(3), 1994, pp. 305-311
When compared to European Large White, Chinese Meishan pigs have high
levels of circulating ACTH and cortisol, and a reduced behavioural rea
ctivity in various challenging situations such as exposure to a novel
environment, two characteristic features of depression. We investigate
d whether this association is genetically built in or whether these ps
ychobiological characteristics are fortuitously associated. Six-week-o
ld piglets from the segregating F2 crosses between the Meishan and Lar
ge White breeds were studied in a standardised protocol of novel envir
onment exposure. As expected from the genetic diversity, a wide range
of variation was recorded for behavioural reactivity (locomotion, voca
lisations). ACTH, cortisol, and glucose were measured in blood samples
taken immediately before the test and at the end of the session. Agai
n these measures varied considerably between animals, and the continuo
us distribution of the scores suggested that they are under control of
numerous genes. Furthermore, no correlation could be found between ne
uroendocrine and behavioural measures. This result demonstrates that t
he association between high ACTH/ corticosteroid levels and a low beha
vioural reactivity is not genetically controlled.