3.4.1.2. Enkephalins
Similar to their effects on beta-endorphin, androgens increase
concentrations of enkephalin peptides in many brain regions. In intact
male rats, chronic treatment with nandrolone increases met-enkephalin
concentrations in the hypothalamus and striatum (Johansson et al.,
2000a) and under some (but not all) conditions in the periaqueductal
gray area (cf., Johansson et al., 2000a; 2000b). Intact male rats also
have greater concentrations of met- and leu-enkephalin in the anterior
pituitary than intact female rats, and castration reduces these
concentrations to those observed in females (Hong et al, 1982; Yoshikawa
& Hong, 1983). Chronic administration of the testosterone metabolite,
DHT, (but not testosterone) increases concentrations of both met- and
leu-enkephalin in the anterior pituitary following castration (Yoshikawa
& Hong, 1983). One exception to these findings is the observation that
chronic treatment with testosterone in intact males decreases met- and
leu-enkephalin concentrations in the anterior pituitary (Yoshikawa &
Hong, 1983).