Fetal mammal bioassays

Olfactory and gustatory stimuli cross the placental barrier (Smotherman Robinson 1987 Keeler 1988) and are present in the fetal blood and amniotic fluid (Hauser et al. 1985 Nolte et al. 1992). These substances can stimulate olfactory and taste receptors (Bradley Beidler 1970 Maruniak et al. 1983), stimulate ingestive behaviors (Nolte Mason 1995), and possibly influence receptor development (Bradley Mistretta 1980). 

Fluids from the fetal environment can be collected for chemical assays from sacrificed or anesthetized subjects. Nolte et al. (1992) collected samples of anmi-otic fluid, allantoic fluid, fetal blood and maternal blood to ascertain whether garlic crossed the placental barrier from mother to fetus. Briefly, a uterine horn and fetus were exteriorized from a ewe at approximately 110 days of gestation, under halothane general anesthesia. Samples were aspirated with a syringe before 

Drinking tests are feasible when testing older subjects. Nolte and Mason (1995) used a single-choice drinking test to assess pup response to trigeminal irritants they were exposed to in utero. First, pups were adapted to an 18-h water deprivation schedule. Pups were presented with tap water in a 10 ml graduated sipper 

Grace and Russek (1969) rated the reactions of canine pups, on the day of birth, to drops of taste stimuli placed on their tongue. Distilled water and test solutions were introduced in random order with drop pipettes, while two observers independently recorded the response. Their response categories were (1) clear rejection (spitting, vomiting, or movement away from the drop pipette) (2) weak rejection (less intense aversive reaction with occasional movement toward pipette) (3) indifference (no evident reaction) (4) weak acceptance (swallowing and movement toward pipette with an occasional movement away and (5) clear acceptance (rapid swallowing, obvious movement toward the pipette) (Jacobs 1964). 

Young rat pups (10 days) also form taste aversions to flavors in milk. Preweanling rats, however, will not form aversions if flavors are presented while they are attached to a nipple (Martin Alberts 1979). 

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