3.4.1 Opioid Peptides
Both castration and administration of exogenous androgens influence the concentrations of opioid peptides and opioid receptors (for review, see Nyberg & Hallberg, 2012; Mhillaj et al., 2015; Wood, 2008). These effects often vary across neuroanatomical loci, but some general patterns are evident from the existing literature.