Late-emerging effects of perinatal undernutrition in neuronal limbic structures underlying the maternal response in the rat.

Maternal care in the rat is an ancient behavioral response to specific multisensory inputs widely integrated in a complex forebrain, limbic and brain stem network to meet the basic needs of the young. Early undernutrition interferes with the morphofunctional organization of the brain, including maternal circuitry. The late-emerging effects of pre- and neonatal undernutrition on nest building and pup retrieval by lactating Wistar rats were correlated with dendritic arbor and perikaryon measurements (Golgi-Cox) in layer II pyramidal neurons of the anterior cingulate cortex, layer III pyramidal neurons of the medial prefrontal cortex and multipolar basolateral amygdala neurons examined on lactation days 4 and 12. In the underfed group, pregnant F0 dams received different percentages of a balanced diet. After birth, prenatally underfed (F1) pups continued the undernutrition by remaining with a nipple-ligated mother for 12 h. Weaning occurred at 25 days of age, and pups were subsequently provided an ad libitum diet. At 90 days of age, F1 dams were maternally tested. Early underfed dams showed significant reductions in nest building and prolonged retrieval latencies for grasping pups by inappropriate body areas. The behavioral alterations were concurrent with highly significant reductions in the somatic cross-sectional area and perimeter, spine density and dendritic crossings of cingulate cells and medial prefrontal cortical pyramids, as well as smaller effects on amygdala neurons. The anatomical findings suggest different postsynaptic organizations that may affect the neuronal excitability stages for the integration and encoding of cues triggering the altered maternal response components of early underfed dams.