Competing appetitive processes in the lactating, maternal rodent: Natural and pharmacological stimuli

The experiments described in this dissertation examine the interaction between the appetitive components of maternal behavior and cocaine-seeking behavior. A classical method to assess the motivational properties of any stimulus is conditioned place preference, based on Pavlovian conditioning. Briefly, a stimulus is conditioned to a distinct context, and the preference for the conditioned context is tested in a stimulus-free state. Chapter 1 describes the development of the place preference paradigm to simultaneously investigate the reinforcing properties of two competing stimuli.; This novel paradigm addresses a fundamental issue—would lactating, maternal rodents (dams) prefer a context conditioned with cocaine or their own offspring (pups)? Chapter 1 demonstrates that the reinforcing properties of cocaine and pups vary across the postpartum period. In the late postpartum period, the majority of dams prefer the cocaine-conditioned context. In contrast, dams in the early postpartum period prefer the pup-conditioned context. In the middle postpartum period, dams prefer either the cocaine- or pup-conditioned context.; Dams in the middle postpartum period provide a unique opportunity to compare the different preference groups concurrently. Chapter 2 characterizes maternal aggression, locomotor activity, open field activity, and place preference of dams during the middle postpartum period. Chapter 2 demonstrates that all of the dams behave normally with no differences between the preference groups. Therefore, these results establish that the preference for a stimulus-conditioned context is manifested through another mechanism.; Chapter 3 investigates the neural substrates through analysis of c-Fos and cocaine-and amphetamine-regulated transcript peptide (CART) immunoreactivity in the preference groups from Chapter 2. Chapter 3 demonstrates that during the appetitive state, in which a preference for a stimulus-conditioned context is measured, specific brain regions within the reward pathway for drugs of abuse and those implicated in the reinforcement processes supporting maternal behavior express increased levels of c-Fos- and CART-IR. Structures not associated with reward processes exhibit no changes in c-Fos- or CART-IR. The qualitative nature of the stimulus, in this case natural or pharmacological, could utilize different components of the reward system for the perception, initiation, and conditioned response associated with the stimulus.