Disruption of maternal behavior by substance abuse resulting in higher levels of maternal neglect towards infants is well documented in human and animal research, while the associated neural mechanisms remain unclear. Several rodent studies indicate that cocaine-exposed maternal females may be less motivated to spend time with pups compared to non-cocaine exposed mothers. One possibility is that pup stimuli, which are known to promote maternal responding in normal mothers, are perceived as less motivating in cocaine-exposed mothers. Motivated behaviors are modulated by dopamine activity in the mesoaccumbens pathway. Fast dopamine release events in the ventral striatum, i.e. dopamine transients, are neural signals of reward prediction occurring at the detection of salient stimuli and often precede approach to a reinforcer. We hypothesize that dopamine transients in rat mothers are triggered by pup stimuli and facilitate normal pup-directed maternal behaviors, while cocaine-treated mothers have blunted DA release to stimuli from their pups that correlates with less maternal response and is driven by a combination of maternal dopamine alterations to cocaine and altered stimuli produced by the cocaine-exposed pups. We propose to use fast scan cyclic voltammetry to measure dopamine release in an established rodent model of maternal behavior. Thus, we will determine whether maternal cocaine exposure during pregnancy, which reduces pup-directed behaviors, also diminishes maternal dopamine release to pup cues. We will use a two-step approach: we will profile dopamine transients in rodent mothers first as they respond to their litters, and second in response to selected pup cues separately from the whole litter. Together, results from these experiments will (1) determine relationships between specific pup-associated stimuli, normal maternal behavior and dopamine transients, and (2) verify how gestational cocaine use alters these relationships in the mother-infant dyad. The data from these studies will provide a solid foundation for future research concerning the causality and biochemical underpinnings of phasic dopamine signals in maternal behavior and their dysregulation by chronic cocaine and will inform our understanding of human maternal neglect in drug-abusing mothers.
This project seeks to understand the neurobiology of maternal behavior, and how maternal cocaine use alters reward value of infant cues relevant to maternal care. The results may lead to new treatment interventions to mitigate the effects of maternal drug abuse.