Parental behavior in the mouse: effects of lesions in the entorhinal/piriform cortex

The effects of bilateral radiofrequency lesions in the region of the entorhinal and piriform cortex (ENT/PIR cortex) on pup-retrieving and ultrasound-elicited pup-searching behavior were investigated in ovariectomized estrogen-treated female mice, which were sensitized to pups by co-caring for a litter for 5 days together with the mother (FoEBex), as well as in primiparous lactating females (Flact). A further group of FoEBex were rendered anosmic by an intranasal treatment with zinc sulfate-solution before the sensitization period and tests for parental motivation. Both pup-retrieving and pup-searching behavior were disturbed to the same extent by ENT/PIR lesions and ZnSO4-induced anosmia in FoEBex. In Flact, however, pup-retrieving was not affected by the lesion, while ultrasound-recognition leading to pup-searching was disrupted. The present data suggest sensitization to pups as a case of olfactory learning and thus, the effects of the ENT/PIR lesions are regarded as anterograde olfactory amnesia. From the present data and results reported in the literature, it is suggested to differentiate between the neural substrates processing stimuli relevant for the appetitive component (pup-searching) of parental behavior (among others, the region of the entorhinal and piriform cortex), and the mechanisms regulating the consummatory component (pup-retrieving).