Galanin in human plasma

The neuropeptide galanin has important effects on hormone secretion from the hypothalamus and pituitary, and it may also be involved in central biological processes such as pain, memory, and food intake. Yet, there is limited knowledge about how these processes are reflected by circulating galanin. To study the levels and molecular forms of galanin in the human circulation, plasma was analysed from 26 healthy subjects, 14 women and 12 men, using two extraction methods and a specific radioimmunoassay for human galanin. Galanin-LI levels in unextracted plasma were higher (141-191 pmol/L) than after immunoextraction (3.4-30.7 pmol/L) and Sep Pak extraction (2.2-12.6 pmol/L). Galanin immunoreactivity after Sep Pak and immunoextraction correlated (r = 0.74, p<0.001). Galanin-LI levels were significantly higher in the men than in the women (p = 0.01) after Sep Pak extraction. A small increase in galanin-LI was seen with age in the women (r = 0.54, p < 0.05). The proportion of Sep Pak extracted galanin-LI increased with age in the women (r = 0.73, p < 0.05)) but not in the men.