NEURONS IN THE LATERAL SUBDIVISION OF THE HABENULAR COMPLEX MEDIATE THE HORMONAL ONSET OF MATERNAL-BEHAVIOR IN RATS

Expanding on research showing that radio-frequency-induced lesions of the habenular complex disrupt the hormonal onset of maternal behavior in rats, we explored the importance of neurons in the lateral (Lhb) su bdivision of the habenular complex for the onset of maternal behavior. On Day 12 of pregnancy, bilateral cytotoxic lesions were produced in the Lhb with kainic acid or, as a control, just dorsal in the medial h ippocampus. A 3rd group had radio-frequency-induced Lhb and medial (Mh b) lesions. On Day 16 of pregnancy, Ss were hysterectomized-ovariectom ized, given estradiol, and tested 48 hr later for 10 days. Neuroanatom ical tracing with fluoro-gold was then used to directly quantify the e xtent and location of Lhb neuron loss and to verify that Mhb neurons w ere intact. Cytotoxic lesions of the entire Lhb prevented the onset of all components of maternal behavior compared with controls. Results s how that neurons in the Lhb, not the Mhb, are important for onset of m aternal behavior in rats.