Development of the Gusto Facial Reflex in Perinatally Undernourished Rats

Abstract

In the rat, the taste system plays a critical role in motivating the animal to consume nutrients and avoid toxic substances. In neonatal rat the orofacial movements can be modified by the application of sucrose and quinine in the mouth, producing ingestion or rejection responses, respectively, but there is no information available on the gusto facial reflexes (GFR) under perinatal fasting. The aim of the present study was to determine how undernutrition can affect the development of orofacial responses to sucrose, quinine, and NaCl during early development. Pregnant dams were undernourished by being given 50% of a balanced diet from G6 to G12, 60% from G13-G18, and 100% from G19-G21. On postpartum days 0 - 9, prenatally underfed (UG) pups continued the undernourishment by remaining for 12 h with a foster dam and 12 h with a nipple-ligated mother. Stimuli were presented as a single droplet of sucrose (S), sodium chloride (NaCl), quinine hydrochloride (Q), and water (W) onto the lips at 1, 3, 5, 7, and 9 days of age, and mouth-opening frequency (MO) and lip-licking frequency (LL) were analyzed. The results show consistent effects associated with age, but not with diet, except in the cases of 0.01 M Q, which provoked in the UG subjects increased MO and the reduction of LL, and 0.1 M Q, which consistently reduced both responses. Moreover, S provoked increases in both MO and LL at 0.1 M while NaCl and water elicited minimal effects on GFR. These data suggest that perinatal undernutrition affects the basic components of the gustatory system necessary to produce GFR in the first postnatal days by possibly interfering with the integration of taste input for food learning and the hedonic aspects of gustatory cues.