in decreased OXT levels in the hippocampus (Kovacs et al., 1987). Chronic morphine treatment in rats produced region-specific alterations in brain OXT expression, with decreased Oxt mRNA in the hypothalamus (SON) and NAc and increased mRNA expression in the VTA and locus coeruleus (You et al., 2000). Further, withdrawal from morphine induced a decrease in hypothalamic OXT peptide levels and concomitant increase of OXTR binding in the lateral septum (LS) and amygdala (Zanos et al., 2014). Similarly, naloxone-precipitated morphine withdrawal increased plasma OXT levels, as well as the firing rate of oxytocinergic neurons in the SON of chronically morphine treated, lactating rats (Bicknell et al., 1988), as well as increased expression of Fos protein within the SON (Johnstone et al., 2000) and OXT mRNA levels within the PVN (Laorden et al., 1998) in opiate dependent rats.
