Tactile,maternal, and pharmacologic factors involved in the “transport response” in rat pups

A series of eight experiments was run to characterize the potentiation of the transport response reported with tactile stimulation. Experiments 1A–C were designed to investigate the types of tactile stimulation that could potentiate an initially weak transport response. Experiments 2A–C were designed to assess the effect of maternal/littermate deprivation on responsiveness to external stimuli in 9- and 16-day-old rat pups. Experiments 3A and 3B were designed to investigate, pharmacologically, underlying mechanisms for the transport response potentiation effect. It was found that if the initial stimulus in producing a strong transport response is inadequate, additional tactile stimulation can potentiate the response. The additional stimuli work best if they are diffuse, if discrete inputs can summate over areas, or if they encompass the snout area. It also was found that isolation could lead to increased responsiveness to stimuli normally eliciting or potentiating the response in 9- and 16-day-old rats. Finally, results indicate that both dopaminergic and beta-noradrenergic systems are important in the response potentiation seen with maternal/littermate deprivation.