“…It is possible that morphine administration alters the endogenous opioid system in brain regions such as POA (Hammer & Bridges, 1987;Hammer, Mateo, & Bridges, 1992;Jacobson, Terkel, Gorski, & Sawyer, 1980;Lee, Clancy, & Fleming, 2000;Vernotica, Rosenblatt, & Morrell, 1999;Wellman et al, 1997), amygdala (Fleming & Walsh, 1994;Komisaruk et al, 2000;Morgan, Watchus, Milgram, & Fleming, 1999), and/or nucleus accumbens (Fleming & Walsh, 1994;Keer & Stern, 1999;Lee et al, 2000;Vernotica et al, 1999), which are thought to be involved in maternal behaviors. Morphine also may induce somatosensory and/or olfactory alterations that might disrupt maternal behaviors (Fleming & Walsh, 1994;Kinsley et al, 1995;Numan & Numan, 1995).…”