BEHAVIORAL-RESPONSES OF THE CHRONICALLY INSTRUMENTED SHEEP FETUS TO CHEMOSENSORY STIMULI PRESENTED IN-UTERO

Fetal sheep were surgically prepared on Days 113-114 of gestation with an array of chronic instruments for recording electromyographic data (EMG) in oral-facial, axial, and limb muscles and heart rate (FHR). Fe tuses also were fitted with an intraoral catheter for infusion of chem osensory fluids (isotonic saline, quinine, colostrum, sucrose) onto th e surface of the tongue. Individual subjects received chemosensory inf usions on Days 134-137. Fetuses showed consistent oral responses to qu inine and milk, but did not respond to isotonic saline or sucrose. Dif ferent patterns of motor responses suggested that fetuses discriminate d among different concentrations of quinine. The expression of tachyca rdia to quinine and bradycardia to milk also suggested differential re sponding to chemosensory fluids that differ in hedonic qualities. Deta iled characterization of fetal responses to these stimuli in utero con firm the functionality of the gustatory system in the sheep fetus near term.