Social isolation increases cholecystokinin mRNA in the central nervous system of rats

To investigate cholecystokinin (CCK) mRNA changes induced by social isolation rats were isolated in single cages soon after weaning for 30 days. They were then sacrificed and their brains removed for in situ hybridization (ISH) study. Control animals were housed in groups of 6 per cage for the same period. ISH was performed using a 32P-labelled oligonucleotide probe complementary to CCK-8 mRNA and the results analysed by computerized densitometry. They showed a significant increase (from 59.5-152.3%) in CCK mRNA expression in the basolateral amygdala, cortex, CA1, dorsal raphe nucleus, geniculate body and ventral tegmental area of isolated rats. These results suggest that social isolation may influence CCK gene expression.