Effects of noradrenergic alpha-2 receptor antagonism or noradrenergic lesions in the ventral bed nucleus of the stria terminalis and medial preoptic area on maternal care in female rats

Abstract

Rationale Maternal behavior in laboratory rats requires a network of brain structures including the ventral bed nucleus of the stria terminalis (BSTv) and medial preoptic area (mPOA). Neurotransmitter systems in the BSTv and mPOA influencing maternal behaviors are not well understood, although norepinephrine is an excellent candidate because the BSTv contains the densest noradrenergic fiber plexus in the forebrain and norepinephrine in the mPOA is known to influence other female reproductive functions. Objectives We hypothesized that downregulated noradrenergic activity in the BSTv and mPOA is necessary for mothering. Methods Postpartum mother-litter interactions were observed after BSTv infusion of yohimbine (an α2 autoreceptor antagonist that increases norepinephrine release), and after BSTv or mPOA infusion of the more selective α2 autoreceptor antagonist idazoxan. Lastly, noradrenergic input to the BSTv/mPOA was selectively lesioned in nulliparous rats with anti-DBH-saporin to determine if this would facilitate mothering. Results BSTv yohimbine almost abolished retrieval of pups but did not significantly affect dams’ ability to initiate contact, lick or nurse them. BSTv idazoxan disrupted retrieval somewhat less than yohimbine, but significantly reduced nursing. mPOA idazoxan impaired retrieval more severely than that found after BSTv infusion. Anti-DBH-saporin almost eliminated noradrenergic terminals in the BSTv and reduced them by over 60% in the mPOA, but did not promote maternal responding. It also did not affect females’ anxiety-related behavior. Conclusions Downregulated noradrenergic activity in the BSTv and mPOA is necessary for postpartum maternal behavior in rats, but eliminating this system alone is insufficient to promote maternal behaviors in nulliparous females.

Common and divergent psychobiological mechanisms underlying maternal behaviors in non-human and human mammals

“…With regards to the traditional neurotransmitter systems, mother rats have higher dopamine (DA) and serotonin turnover in the mPOA compared to nulliparous rats (Lonstein, Dominguez, Putnam, De Vries, & Hull, 2003; Olazabal, Abercrombie, Rosenblatt, & Morrell, 2004), and DA and gamma amino-butryic acid (GABA) are released into the mPOA when ewes interact with lambs (Kendrick et al, 1992). These findings are consistent with experiments demonstrating that DA, GABA or noradrenergic receptor modulators infused into the mPOA/BSTv can positively or negatively affect maternal behaviors (Arrati, Carmona, Dominguez, Beyer, & Rosenblatt, 2006; Miller & Lonstein, 2005; Smith, Holschbach, Olsewicz, & Lonstein, 2012; Stolzenberg et al, 2007). The neurochemicals emanating from the mPOA and released onto its afferents to positively control maternal behavior include GABA (Lonstein and DeVries, 2000c; Tsuneoka et al, 2013), OT (Shaharokh et al, 2010), and galanin (Wu et al, 2014).…”

Motherhood and infant contact regulate neuroplasticity in the serotonergic midbrain dorsal raphe

“…Immunoreactivity was differentiated from background by using an optimized light threshold that was also kept constant for every image. Standardized traces were superimposed upon the images and the area covered by pixels above the standardized light threshold was calculated using NIS-Elements, as described elsewhere (Smith et al, 2012). …”

Differential postpartum sensitivity to the anxiety-modulating effects of offspring contact is associated with innate anxiety and brainstem levels of dopamine beta-hydroxylase in female laboratory rats

“…Behavior testing occurred between 1400 and 1600 h. To avoid complications such as habituation to the testing apparatus or changes in the neurobiological underpinning of behavior sometimes associated with repeated testing in the same behavioral paradigm (File, 1990; Bourin and Hascoët, 2003), pre-mating anxiety was assessed for 10 min with a light–dark box and postpartum anxiety was assessed for 10 min with an elevated plus maze using methods previously described in detail (Lonstein, 2005; Miller et al, 2011; Smith et al, 2012). Both paradigms are based on rats’ innate aversion to bright light and open spaces, such that lower anxiety is associated with more time spent in the light chamber of the light–dark box and a greater percentage of time spent in the open arms of the elevated plus maze.…”