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The present report examined the morphology of fungiform papillae in adult rats that received bilateral chorda tympani transection at 10 days of age. Tongue tissue was examined using surface-structure analysis. Counts were made of fungiform papillae with a pore, fungiform papillae with no pore and fungiform papillae with a keratinized conical surface; a feature referred to as "filiform-like. " Neonatal chorda tympani nerve transection resulted not only in a loss of taste buds but also in a permanent loss in numbers of fungiform papillae. Compared with an average of 152 fungiform papillae in sham-operated control rats, there was an average of only 54 fungiform papillae after neonatal chorda tympani transection. Nearly 80% of these fungiform papillae in neonatal chorda tympani transected rats were filiform-like. No filiform-like papillae were noted in sham-operated rats. These results suggest that the chorda tympani nerve is necessary during an early postnatal period of development to maintain normal fungiform papillae morphology.

Evidence for an association between early pregnancy sickness and offspring salt (NaCl) preference has been obtained from studying offspring as young adults and as infants. To determine whether the association between early pregnancy sickness and salt preference of offspring is secondary to familiar similarity in salt preference, the present study examined the self-reported salt intake and dietary cravings and aversions of pregnant women. Women who reported little or no vomiting (n = 108) were compared to women who reported moderate to severe vomiting (n = 21) during pregnancy. The women's self-reported salt use and reported cravings and aversions for common food were measured via survey for time periods prior to and during their current pregnancy. Women did not differ in reported salt use prior to pregnancy as a function of their pregnancy symptoms. Women reported more aversions during, than prior to, pregnancy (p < 0.05). Women with more severe vomiting reported a greater number of aversions (p < 0.05) both prior to and during pregnancy. There was a significant association between experiencing cravings and aversions prior to pregnancy and experiencing craving and aversions during pregnancy (p < 0.05). These findings do not provide evidence for an association between dietary levels of sodium and the likelihood of experiencing severe pregnancy symptoms. Therefore, these data do not support the suggestion that reported elevations in salt preference in offspring of women with moderate to severe vomiting during pregnancy are mediated by familial dietary practices.

Food aversions that are acquired as a result of unpleasant experiences with foods represent a potent defense mechanism against poisoning. However, this powerful and durable form of conditioning can also contribute to avoidance of foods that are not poisonous, and are, in fact, quite nutritious. This is because such foods may be coincidentally associated with unpleasant gastrointestinal symptoms, sometimes due to transient, unrelated illness, or unpleasant drug side effects. Most of the studies of naturally occurring learned food aversions in humans have been focused on subjects of college age, so we have limited information about the extent to which such food aversions occur in the elderly. Additionally, most studies have employed questionnaire or interview methods that may have some significant limitations in the accurate assessment of the incidence of food aversions. Thus, although food aversion learning has been thoroughly documented in the animal laboratory, its role in everyday food selection in humans, including the elderly, remains relatively unclear.

To examine the development of strain differences in the response of the chorda tympani nerve (CT) to NaCl, integrated CT responses to NaCl were recorded from Wistar and F344 rats between 15 and 36 days old. NaCl responses before and after the application of amiloride were expressed relative to 0.5 M NH4Cl as a standard. At 15-17 days old, there were no significant strain differences in the magnitude of NaCl responses. Strain differences emerged at 21-23 days old with responses of F344 rats significantly higher than those of Wistars; these differences became more pronounced at 34-36 days old. Amiloride significantly reduced responses to NaCl at all ages and eliminated any differences between the strains. Changes in neural responsiveness correspond with the emergence of the behavioral expression of F344 salt aversion.

Fischer 344 (F344) rats fail to prefer sodium chloride (NaCl) solution to water, and this behavior is dramatically altered by bilateral transection of the chorda tympani nerve (CTX). Tests of retention and generalization of a conditioned taste aversion (CTA) to 0.15 M NaCl were used to assess alterations in salt taste perception after CTX. A CTA was established to 0.15 M NaCl in groups of F344 and Wistar rats after two pairings with LiCl (IP, 2% body weight; 0.15 M). After conditioning, animals received bilateral CTX or sham operations. Approximately 2 weeks after surgery animals were tested for retention of the CTA. Aversion to 0.15 M NaCl was evident in CTX and SHAM rats that had been conditioned prior to surgery, with no apparent difference in magnitude as a function of surgical condition. Thus, although CTX profoundly alters F344 rats' hedonic response to NaCl, it does not alter perceptual characteristics so markedly that NaCl is no longer recognized as the stimulus presented during aversion conditioning. Rather these studies suggest that in both the F344 and Wistar strains the chorda tympani nerve is not necessary for retention of a presurgical CTA to NaCl. These studies, therefore, do not provide evidence of changes in NaCl perceptual "quality" as a consequence of CTX either in F344 rats, where such changes were indicated by the preference data, or in the Wistar rat, where they were not.

The present experiments examined whether behavioral conditioned responses (CRs) develop to LiCl-paired contextual and odor stimuli, and whether these CRs are similar to the behaviors observed following the administration of the drug. During conditioning, a novel context (Experiment 1) or a novel odor (Experiment 2) was paired with LiCl injections, and the CRs which developed to these stimuli were assessed during testing. Suppression of general activity occurred after LiCl exposure and after exposure to the lithium-paired context and odor. However, the actual behaviors which emerged as conditioned responses were distinctly different from those which were elicited by the drug itself. Lying on belly was the predominant unconditioned response to LiCl. Freezing was the predominant CR to the context, whereas gaping was the predominant CR to the odor. These outcomes are discussed and compared to previous results using a taste stimulus.

The role of vasopressin (VP) in a sexually dimorphic behavior, the extinction of a conditioned taste aversion, was investigated in male and female rats of three different genotypes. This behavior was examined with a two bottle test in the wild-type Long-Evans (LE) rats, and then in partially VP deficient heterozygous (HET-BB) and completely VP deficient homozygous (HO-BB) Brattleboro rats. In Experiment 1, non-deprived male and female LE rats were given aversions to a sucrose solution by pairing it with a LiCl injection. The rate of extinction of the aversion upon reexposure to ad lib sucrose solution was examined and observed to be sexually dimorphic. Female LE rats extinguished at a significantly more rapid rate than males. Experiment 2 compared HET-BB and HO-BB male and female rats using the same paradigm. Neither of these VP-deficient groups showed sexual dimorphism of the extinction behavior. The data suggest that intact VP levels are necessary to observe the expression of this sexually dimorphic behavior.

The development of learned aversions to the available diet has been shown to contribute to the anorexia and weight loss which accompany the growth of certain tumors, including the Leydig LTW(m) tumor. Estradiol infusions were found to closely mimic the effects on food intake and food preference seen after Leydig LTW(m) tumor implants. That is, reductions in food intake and the development of severe aversions to a target diet available during hormone infusions were seen. Lesions of the area postrema greatly attenuated these effects of estradiol infusions. Similar lesions have been shown to have parallel effects on the LTW(m) tumor syndrome. These findings strongly implicate the elevations of circulating estrogens which accompany the growth of LTW(m) tumors in generating the symptoms of anorexia and diet aversions.

In order to determine whether some nutrients are more salient targets than others for the development of learned taste aversions a large group of normal human subjects were surveyed about their experiences with such aversions. The targets of these spontaneously occurring food aversions were identified and classified into general food categories. A prominent category for human aversions proved to be foods which were protein sources. This finding was similar to our observations in the clinical setting as well as those we have obtained using an animal model. It suggests that taste and/or postingestive properties of protein foods may make them particularly salient targets for food aversion learning.

Effects of taste deprivation and selective taste exposure during the suckling period on adult preference for flavored solutions was examined. Taste deprivation was achieved by rearing rat pups "artificially," in individual cups with intragastric feeding from Postnatal Days 4 through 17 or 18. In the first study the effects of artificial rearing on male Long-Evans rats were examined. In the second study female Wistar rats were exposed to a single tastant, sucrose, which was introduced on a background of taste deprivation. Results of both studies were similar. No differences in taste sensitivity or preference were detected between animals subjected to taste deprivation or selective taste exposure and their normally reared littermates. These results suggest that suckling stimulation is not necessary for normal taste development and that the taste system of the rat is not particularly susceptible to the influence of early experience. Other interpretations of these results are also discussed.

Cephalic phase insulin release (CPIR) was examined in women with anorexia nervosa and in lean, age matched controls. Following an overnight fast, a palatable food was presented to subjects and plasma insulin was measured at baseline and every minute for a 10 minute period following the presentation of the food. Elevation in plasma insulin occurred five minutes after food presentation in the anorexic group only. The finding of a significant CPIR in anorexics but not controls was unexpected and tends to rule out a deficient cephalic insulin response as a contributor to the self-starvation observed in anorexia nervosa.

LTW(m) Leydig cell tumors were removed from Wistar Furth rats after the animals had developed anorexia and strong aversions to a novel diet consumed during tumor growth. Previous studies had reported recovery from anorexia within 24-48 hr of tumor excision but had not measured diet preference to find out if food aversions persisted beyond recovery. In the present study, which allowed the rats to choose freely between the aversive diet and a nonaversive diet for several weeks, aversions persisted from four to 25+ days. No signs of anorexia were evident during this testing phase, which followed 10 days of post-operative recuperation in which the rats were restricted to a diet of familiar laboratory chew. These results are consistent with the hypothesis that certain anorexigenic tumors, such as the LTW(m), can substantially affect food selection long after their direct effects on appetite have dissipated.