Mouse taste preference tests: why only two bottles?

Two-bottle tests have been used extensively to measure the preference for taste and nutrient solutions but there has been little work with tests involving more than two bottles. Here, we compare the results obtained in two-bottle tests with those obtained in three- and six-bottle tests. In Experiment 1, we measured the preferences for 2 mM saccharin, 50 mM citric acid, 0.3 mM quinine hydrochloride and 75 mM NaCl displayed by 129X1/SvJ (129) and C57BL/6J (B6) mice. Mice drank more taste solution when they received two bottles providing taste solution and one providing water than when they received either a standard two-bottle test or two bottles providing water and one providing taste solution. The three-bottle tests also revealed the left spout side preferences of the 129 strain and were generally better at distinguishing between the 129 and B6 strains (i.e. were more sensitive) than were the two-bottle tests. In Experiment 2, we measured intakes and preferences in tests with six bottles, with one, two, three, four or five containing 75 mM NaCl and the rest containing water. NaCl preferences were monotonically related to the number of NaCl spouts available. A follow-up experiment found similar results whether the index of ingestion was volume intakes or licks. This argues that spillage cannot account for the effect of spout number on taste solution intake. Together, the results suggest that (i) the number of bottles of taste solution and water has a profound influence on taste solution intake and preference, and (ii) three-bottle tests may be more sensitive than two-bottle tests in many circumstances.

The number of male pups within a litter of NMRI mice is associated with the dam's food preferences late in pregnancy

Pregnancy related differences in food preferences and food intake are well recognized in animals and humans. Changes in maternal hormonal profiles are supposed to be implicated in such a phenomenon. Since fetal sex hormones are excreted in their dams' bloodstream, they can affect the behaviour of mothers during gestation. We investigated whether there was a relationship between the number of male pups within the litter and food preferences in pregnant mice. In the first experiment we found that, parcelling out the effect of litter size, the number of male fetuses was positively correlated to maternal testosterone levels on pregnancy day (PD)18. In the second experiment we showed an association between the number of males and the consumption of a 0.25% saccharin solution on PD18, controlling for litter size and baseline (before pregnancy) saccharin intake. In the third experiment, mice on PD18 were placed in a test cage and underwent a 1-h binary choice test between two unknown unpalatable diets, a high fat diet (HFD) and a sweet mesh diet (HSD). Results revealed that the number of males was negatively associated with the preference for the HFD at birth. These results are consistent with the hypothesis that the behavioural profile of dams can be associated with fetal gender composition.

Blockade of cortical muscarinic but not NMDA receptors prevents a novel taste from becoming familiar

Exposure to a novel taste solution in the rat is followed by a decrease in its intake known as neophobia. This effect gradually disappears, and consumption increases from the second presentation of the taste (attenuation of neophobia), reflecting that the animal learned that it is safe to drink it. Conversely, if gastric malaise is induced after first intake, the rat will develop a long-lasting aversion (conditioned taste aversion). Previous attempts to elucidate the physiological nature of taste memory trace stems only from procedures that require malaise to measure taste memory. Here we assess the relevance of both muscarinic and N-methyl-d-aspartate receptors, known to be involved in conditioned taste aversion, on taste memory using a nonaversive procedure (attenuation of neophobia learning). Attenuation of neophobia was impaired by the muscarinic receptor antagonist, scopolamine, microinjected 20 min before, immediately after or up to 2 h after the first taste experience, suggesting that muscarinic receptors are involved in the acquisition and consolidation of attenuation of neophobia learning. However, the N-methyl-d-aspartate receptor antagonist, d,l-2-amino-5-phosphonovaleric acid, did not affect attenuation of neophobia even when the same dose of the drug was able to disrupt conditioned taste aversion learning, which suggests that attenuation of neophobia learning would be independent of N-methyl-d-aspartate receptors activity in the insular cortex. The neophobic response induced by strong saccharin presentation was not affected by either of the treatments given, which rules out any impairment in taste perception. These results indicate that while cortical muscarinic receptors are important in the formation and consolidation of safe memory trace, N-methyl-d-aspartate receptor activity appears to be noncritical.

Taste responsiveness and diet preference in autoimmune MRL mice

One of the most profound behavioural deficits in lupus-prone MRL-lpr mice is blunted responsiveness to sweet solutions. Given the systemic nature of autoimmune/inflammatory disease, it was not clear whether impaired taste sensitivity or motivated response to palatable food underlie this deficit. The present study compares response rates of MRL-lpr mice (which develop disease early), congenic MRL +/+ mice (which develop disease later in life) and non-autoimmune Swiss Webster (SW) mice to different tastes and diets. Healthy SW mice showed the highest responsiveness to palatable stimulation throughout the study. Conversely, the preference for palatable solutions progressively declined in MRL-lpr mice as the disease developed. No differences between the two MRL substrains were seen in responsiveness to quinine or saline, suggesting that blunted responsiveness to palatable solutions cannot be accounted for by reduced taste sensory function (hypogeusia). In addition, changes in response rates to palatable solutions were associated with systemic upregulation of pro-inflammatory cytokines. With a new cohort of mice fed on carbohydrate-rich and fat-rich diets, we also examined whether reduced sucrose intake in MRL-lpr mice can be accounted for by a reduced craving for carbohydrates. Contrary to this expectation, diseased MRL-lpr mice preferred carbohydrate-rich food while consuming a food mass comparable to controls. These results further support the hypothesis that the onset of lupus-like disease alters motivated behaviour, independent of changes in neurologic function and food metabolism.

Physical and emotional stress have differential effects on preference for saccharine and open field behaviour in rats

Stress may influence the sensitivity of subjects to rewarding stimuli and stress modality may differentially affect this sensitivity. This relation was investigated in our animal model using chronic physical (repeated mild foot shocks) and emotional (witness) stress. Previous research has established that the two stressors have differential long-term effects on behaviour, where physical stress caused inactivity in a small open field and emotional stress hyperactivity. Rats were stressed on 5 consecutive days and tested for locomotor activity in a small open field (day 10) and saccharine preference (day 11). The preference for graded concentrations of saccharine over water was used as a measure for their sensitivity to reward. Physical stress treatment induced a long-term decrease both in preference for saccharine and open field activity compared to control treatment. Emotional stress animals showed an increase in open field behaviour activity and a slight increase in saccharine preference. Physical stress seems to cause anhedonia, while emotional stress might cause an increased sensitivity to reward. In conclusion, stress can induce differential long-term effects on sensitivity to positive stimuli and the response to novelty depending on stress modality.

Naltrexone suppresses the late but not early licking response to a palatable sweet solution: opioid hedonic hypothesis reconsidered

Opioid antagonists suppress the intake of sweet solutions, but typically have little effect on the initial rate of drinking. The lack of an early drug response was investigated in the present study because it questions the general idea that opioid antagonists reduce the hedonic response to sweets. The first experiment, which measured the rat's licking response to a sucrose+saccharin (S+s) solution, revealed that naltrexone suppressed S+s intake but not initial lick rates. Experiment 2A indicated that the drug's delayed behavioral effect was not due to the 10-min injection-test interval used. Increasing the interval to 20 min did not reduce the latency of drug action. Experiment 2B tested the idea that rats require several minutes to detect that naltrexone has reduced the hedonic value of the S+s solution. The S+s solution was presented either for 30 min without interruption or for 3 min followed, after a 6-min delay, by another 27-min access. In both test conditions, naltrexone did not suppress S+s licking until 7-9 min of drinking had occurred. However, the drug blocked an "appetizer effect"; a post-delay increase in licking rate produced by the split-session test procedure. Microstructure analysis indicated that in all cases, naltrexone reduced S+s licking by reducing the number of lick clusters rather than lick cluster size. In contrast to these drug effects, Experiment 2C showed that reducing the concentration of the S+s solution decreased initial lick rates. Together, these findings suggest that opioid antagonists do not affect all aspects of flavor hedonics, but may primarily alter the intake-maintaining action of palatable flavors.

Influence of test duration on the sensitivity of the two-bottle choice test

The long-term two-bottle choice test is commonly used as a simple screen to examine the acceptance of taste solutions by rodents. As part of an investigation of factors influencing the sensitivity of the two-bottle choice test, we determined the extent to which test duration influenced test sensitivity. C57BL6/J and 129X1/SvJ mice received four series of eight two-bottle tests, with each test lasting 1, 2, 4 or 6 days. Each series involved sequential tests with water, 2 mM saccharin, 5 and 50 mM citric acid, 30 and 300 micro M quinine hydrochloride, 75 mM NaCl and 10% ethanol. There were significant differences between the strains in intake of saccharin, 5 and 50 mM citric acid, NaCl and ethanol in 4 and 6 day tests, but only saccharin and ethanol in 2 day tests, and 5 mM citric acid and ethanol in 1 day tests. To compare the sensitivity of the tests, we developed an analytical approach based on the comparison of deviations of individual 129X1/SvJ mice from the C57BL6/J strain mean. Our results suggest that to discriminate between strains or treatments when using 'standard' laboratory conditions and methods, 1 day tests are generally inadequate and 2 day tests are useful only if large effects are anticipated. Tests lasting 4 or 6 days are more sensitive, but conducting 6 day tests provides little additional benefit and sometimes is detrimental relative to conducting 4 day tests.

Glutamatergic activity in the amygdala signals visceral input during taste memory formation

Conditioned taste aversion (CTA) is a learning paradigm in which an animal avoids a taste (conditioned stimulus) previously associated with visceral toxic effects [or unconditioned stimulus (US)]. Although many studies have implicated glutamate-mediated neurotransmission in memory consolidation of different types of learning tasks, including CTA, the exact role of this neurotransmitter system in memory formation is not known. Thus, we set out to determine whether glutamate mediates signaling of the US in CTA. We present evidence obtained by in vivo microdialysis that the US (i.p. injection of lithium chloride) induced a dramatic increase in glutamate release in the amygdala and a modest but significant release in the insular cortex. Moreover, CTA can be elicited by intra-amygdalar microinjections of glutamate; consequently, when glutamate is administered just before the presentation of a weak US, a clear CTA is induced. In contrast, the injection of glutamate alone or glutamate 2 h after the suboptimal US did not have any effect on the acquisition of CTA. These results indicate that glutamate activation of the amygdala can partially substitute the US in CTA, thus providing a clear indication that the amygdala conveys visceral information for this kind of memory.

Haloperidol attenuates rewarding and aversively conditioned suppression of saccharin solution intake: reevaluation of the anhedonia hypothesis of dopamine blocking

The dopamine (DA) antagonist, haloperidol, affected the conditioned suppression of a saccharin solution intake (the conditioned stimulus, CS) induced by amphetamine (AMPH) and lithium chloride (LiCl) unconditioned stimuli (USs). Four experiments showed that (a) haloperidol by itself did not reduce saccharin solution intake. (b) When haloperidol was injected between the CS and the US, the conditioned suppression was attenuated; however, (c) this did not occur when haloperidol was injected after the US, indicating that haloperidol affected the perception of the US. (d) This attenuation was found with both rewarding AMPH and aversive LiCl treatments, indicating that the valence of the US was unimportant. Thus, the so-called "anhedonia response" might be due to weakening of US impact. A general salient-stimulus hypothesis was proposed, with the anhedonia hypothesis of DA blocking as its subset.

The effect of hyperbaric oxygen on nasal mucociliary transport

Nasal mucociliary transport was measured in a group of 30 adult patients (eight women and 22 men; age range 21-78 years, mean 47.9 years) treated with hyperbaric oxygen (HBO) therapy and in a control group of 32 adult subjects (two women and 30 men; age range 20-50 years, mean 32.0 years) compressed in a hyperbaric chamber without oxygen therapy. The treated patients breathed 100% oxygen at 250 kPa pressure for 60 min. Subjects from the control group were compressed in the hyperbaric chamber at 250 kPa for 70 min. Nasal mucociliary transport was measured with the saccharin clearance test. After exposure to HBO, the nasal mucociliary transport time was significantly decreased by 26% (P < 0.01) and returned to the original value after 24 h (increased by 8.3%, P = 0.25). In the control group, compressed in air, there were no statistically significant changes. This study shows that simultaneous compression and pure oxygen cause an increase in nasal mucociliary transport. The mechanism of activation of mucociliary clearance is probably the increased oxygenation of blood plasma and enhancement of metabolism in ciliated epithelium.

Oral testosterone self-administration in male hamsters: dose-response, voluntary exercise, and individual differences

Although testosterone was declared a controlled substance in 1990, the potential for steroid dependence is largely unexplored. The present study used food-induced drinking with oral testosterone self-administration in hamsters to determine (1) the dose-response for testosterone reward, (2) links between testosterone self-administration and voluntary exercise, and (3) factors predicting individual differences in androgen intake. Testosterone (1-4 mg/ml) was presented in aqueous solution 3 h/day for 35 days, with and without food. At 3 mg/ml, testosterone maintained fluid intake, even without food (3.0 +/- 0.2 ml/3h). At 4 mg/ml, fluid intake declined to 2.4 +/- 0.3 ml/3h in the presence of food. However, no dose-response relationship between testosterone self-administration and reward was observed. To test the interaction of testosterone and exercise, males drinking testosterone (RUN + T) or vehicle received a running wheel. Additional males self-administered testosterone without exercise. Testosterone intake correlated positively with exercise and negatively with body weight in RUN + T males. Experiment 3 determined the relationship between testosterone self-administration and mating or saccharin preference. There were no statistically significant correlations. However, testosterone self-administration increased mating behavior. These data demonstrate that testosterone is a mild reinforcer. Although preference for androgens is not predicted by mating or saccharin intake, testosterone intake is linked with voluntary exercise.

Mapping of QTL influencing saccharin consumption in the selectively bred alcohol-preferring and -nonpreferring rat lines

The inbred preferring (iP) and nonpreferring (iNP) rat strains were derived from the selectively bred alcohol-preferring (P) and alcohol-nonpreferring (NP) lines. Previously, 381 iP x iNP F2 progeny were generated to identify quantitative trait loci (QTLs) influencing alcohol consumption and preference. Saccharin consumption (ml/48 h) and saccharin intake (ml/kg/day) were also measured in the F2 sample and were significantly correlated with both alcohol consumption and preference (all r > or = .20, p < .0001), suggesting that there might be some QTLs influencing both saccharin and alcohol phenotypes. We have performed a genome screen using F2 animals with extreme saccharin or alcohol consumption to identify QTLs contributing to saccharin-related phenotypes. Lod scores greater than 2.0 were found on chromosomes 3, 16 and 18 in this sample. Additional genotyping was performed in these regions in the full sample of 381 F2 progeny to further characterize these putative QTLs. On chromosome 3, the maximum lod score in the full sample was 2.7 with saccharin consumption. This QTL appears to overlap with a QTL identified for alcohol consumption in the iP and iNP lines and has pleiotropic effects on both phenotypes. Interestingly, this region of rat chromosome 3 is syntenic with mouse chromosome 2, where a QTL influencing alcohol preference has been previously reported. The QTL on chromosome 16 has a maximum lod score of 4.0 with saccharin intake and 2.6 with saccharin consumption. The QTL on chromosome 18 has a maximum lod score of 2.7 with saccharin consumption. Taken together, these data provide the first results of a genome screen for QTLs contributing to saccharin phenotypes in the rat.

Bitter taste of saccharin and acesulfame-K

The relationships among suprathreshold taste responses to acesulfame-K, Na-saccharin and 6-n-propylthiouracil (PROP) were examined in two studies. In the first study, the labeled magnitude scale was used with the high anchor labeled as 'strongest imaginable oral sensation' and in the second study, it was labeled as 'strongest imaginable sensation of any kind'. Results from the two procedures were similar. Individual differences among 65 subjects were seen in bitter responses to acesulfame-K and saccharin. Bitter responses to acesulfame-K ands accharin were positively correlated, but showed no significant relationship with responses to PROP bitterness or with PROP taster groups. Saccharin and acesulfame-K may share a common mechanism for bitter taste reception and transduction, one that varies across individuals and is different from mechanisms mediating bitter responses to PROP. Changing the instructions of the labeled magnitude scale induced a context effect. Ratings of sweetness referenced to the 'strongest imaginable sensationof any kind' were lower than ratings referenced to just oral sensations.

Ringer-Lactate solution versus isotonic saline solution on mucociliary function after nasal septal surgery

Irrigation with isotonic saline is one of the most frequently used solutions after nasal surgery. However, the effect of saline solutions on mucociliary clearance is not well known. In a previous study, it was found that isotonic saline solution had a negative effect on ciliary beat frequency but Ringer-Locke solution had no effect in vitro. In this study we compared the effects of Ringer-Lactate solution and isotonic saline solution on mucociliary transport time before, and after, nasal septal surgery in patients with nasal septal deviation. We found that patients who used Ringer-Lactate solution as irrigation after surgery had a significantly better mucociliary transport time than the patients using isotonic saline solution (p < 0.05). In conclusion, it is better to use Ringer-Lactate solution instead of 0.9 per cent saline solution for nasal irrigation.

Effects of naltrexone on the intake of ethanol and flavored solutions in rats

It has been suggested that the endogenous opioid system may mediate the intake of preferred fluids, perhaps through an attenuation of reinforcement properties causing a subsequent shift in palatability. The purpose of the present study was to investigate the effects of the nonspecific opiate antagonist naltrexone on the intake of 10% ethanol, 0.1% saccharin, 0.0006% quinine, 0.4% saccharin + 10% ethanol, and 0.4% saccharin + 0.04% quinine solutions. Fluid intake was measured in male Long-Evans and Wistar rats under 24-h continuous and 30-min limited-fluid-access drinking paradigms. All rats received injections of naltrexone hydrochloride (10 mg/kg, i.p.) for 5 days after baseline intake measures and were monitored for a further 5 days (after-treatment phase). Results indicated that naltrexone did not affect intake of any solution when fluids were available over 24 h. However, under limited-access conditions, naltrexone caused a decrease in the intake of all fluids except quinine in both rat strains. On the basis of these findings, it is possible that the effects of this dose of naltrexone were not due to any true conditioning effect on the reinforcement properties of ethanol, but perhaps to some nonspecific effect of the drug, such as an alteration in palatability or an attenuation of locomotor activity. As well, due to the inconsistent results in fluid intake across drinking paradigms, the present findings do not provide evidence for an effective role for opiate mediation in ethanol intake as well as any ethanol-sweet fluid intake interactions.

Primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is an inherited condition characterised by functional and/or structural congenital abnormalities of cilia. Presentation is often in the neonatal period, but there are age-related differences in presentation, and diagnosis is often delayed. The usual clinical picture is of recurrent upper and lower respiratory symptoms (rhinitis, glue ear, recurrent cough and sputum production), with mirror image arrangement in 50% of the children. Around 50% males have immotile sperm, but male infertility is not invariable. There are known associations between PCD and complex congenital heart disease, severe oesophageal disease, and more rarely, hydrocephalus and biliary atresia. Diagnosis is with a combination of the saccharine test, nasal nitric oxide, ciliary beat frequency and electron microscopy. Patients should be followed up by specialists familiar with the different ways of managing the upper and lower airway complications.

Chronic morphine treatment exaggerates the suppressive effects of sucrose and cocaine, but not lithium chloride, on saccharin intake in Sprague-Dawley rats

Three experiments examined the effect of chronic morphine treatment on cocaine-, sucrose-, and lithium chloride (LiCl)-induced suppression of saccharin intake in Sprague-Dawley rats. All rats were either water- or food-deprived and then implanted subcutaneously with 1 morphine (75 mg) or vehicle pellet for 5 days. They were then given brief access to 0.15% saccharin and soon thereafter injected with either cocaine (10 mg/kg s.c.), LiCl (0.009 M, 1.33 ml/100 g body weight i.p.), or saline, or, in Experiment 2, given a 2nd access period to either a preferred 1.0 M sucrose solution or the same 0.15% saccharin solution. There was 1 taste-drug or taste-taste pairing per day for a number of days. The results showed that a history of chronic morphine treatment exaggerated the suppressive effects of a rewarding sucrose solution and cocaine but not those of the aversive agent, LiCl. These data provide further support for the reward comparison hypothesis.

Paradoxical effects of ketamine on the memory of fetuses of different ages

Brain N-methyl-D-aspartate (NMDA) glutamate receptors have been implicated as important mediators of both learning and neuronal development. The current study investigated how ketamine (a well-known NMDA-receptor blocking drug) influences taste-mediated conditioned motor responses (CMRs) in perinatal rats. Dams pregnant with either embryonic day 18 (E18) or E19 rat fetuses were injected with 0 or 100 mg/kg ketamine HCl (i.p.). One-half hour later, a reversible spinal block was performed on the dam and fetuses received oral lavage with 10 microl, 0.3% saccharin (SAC) or water (control) in utero. After the oral injection, fetuses received either a saline (control) or lithium chloride (LiCl) injection (81 mg/kg, i.p.). The uterus was replaced and, 2 days later (E20 or E21), some rats received oral lavage with SAC. Other litters were born via normal vaginal delivery or Cesarean section and orally exposed to SAC on post-natal day 3 (P3). Motor responses were observed immediately after the oral lavage of SAC. If SAC had been paired with LiCl in utero, pups generally exhibited conditioned suppression of orofacial movements (as compared to controls). Ketamine significantly attenuated this taste-mediated CMR of animals conditioned on E19. However, the same treatments did not disrupt CMRs of rats treated with ketamine before CS-US pairing on E18. Our findings indicate an age-dependent role for NMDA receptors in the formation of CMRs in perinatal rats.

Memory extinction, learning anew, and learning the new: dissociations in the molecular machinery of learning in cortex

The rat insular cortex (IC) subserves the memory of conditioned taste aversion (CTA), in which a taste is associated with malaise. When the conditioned taste is unfamiliar, formation of long-term CTA memory depends on muscarinic and beta-adrenergic receptors, mitogen-activated protein kinase (MAPK), and protein synthesis. We show that extinction of CTA memory is also dependent on protein synthesis and beta-adrenergic receptors in the IC, but independent of muscarinic receptors and MAPK. This resembles the molecular signature of the formation of long-term memory of CTA to a familiar taste. Thus, memory extinction shares molecular mechanisms with learning, but the mechanisms of learning anew differ from those of learning the new.

Behavioral responses of rats exposed to long-term dietary vinclozolin

Vinclozolin is a fungicide used on food crops with human exposure estimated at approximately 2 microg/kg/day from ingestion; occupational exposure, however, may be greater. The metabolites of vinclozolin have been reported to act as antiandrogens and have adverse effects on reproductive physiology and behavior in animals. Here, pregnant rats were fed soy-free diets containing 0, 10, 150, or 750 ppm of vinclozolin (approximately 0, 0.8, 12, and 60 mg/kg/day for an adult) beginning on gestational day 7, and offspring were continued on these diets through sacrifice at postnatal day 77. Male and female offspring were assessed for changes in several nonreproductive sexually dimorphic behaviors: open field and running wheel locomotor activity, play behavior, and consumption of saccharin- and sodium chloride-flavored solutions. There was a significant interaction of sex with vinclozolin exposure on running wheel activity, which indicated that females in the high-dose exposure group were hypoactive compared to same-sex controls. There was a significant overall effect of vinclozolin exposure on fluid consumption, and high-dose animals showed increased intake of the saccharin solution and decreased intake of plain water while saccharin was available. Effects were more pronounced in females, which drank 40.8% more saccharin than control females, whereas males drank 6.2% more than control males. There were no effects of vinclozolin treatment on play behavior or sodium solution intake. Gestational duration, total and live pups per litter, litter sex ratios, and birth weight were also not significantly affected, nor were body weight and food intake for dams and offspring. These results indicate that long-term dietary exposure to vinclozolin does not have severe toxicological consequences on the nonreproductive behaviors measured here. However, exposure may cause subtle alterations in locomotor activity and consumption of saccharin-flavored solution.

Nitric oxide modulates lithium-induced conditioned taste aversion

Nitric oxide (NO) has been shown to affect the behaviour in animal models of depression, anxiety and avoidance learning. Lithium has marked effect in avoidance learning, an effect that can be modulated via the 5-HT system. Experiments were carried out using the conditioned taste aversion (CTA) paradigm to investigate whether administration of NO-modifying drugs, serotonergic drugs and lithium, alone or in combination, induced or affected a CTA. The NO-precursor L-arginine (L-Arg), the non-specific inhibitor of NOS and guanylate cyclase, methylene blue (MB) and the specific NOS inhibitor 7-Nitroindazole (7-NI) all produced CTAs in a dose-dependent fashion. Furthermore, we found that L-Arg counteracted the CTAs induced by LiCl or MB but failed to modulate the CTA produced by 7-NI. The administration of the selective 5-HT1A agonist, 8-OH-DPAT, counteracted the CTAs produced by MB and 7-NI. In contrast, depletion of 5-HT by p-Chlorophenylalanine did not affect the aversions produced by MB and 7-NI, but counteracted the CTA produced by L-Arg. Our results suggest that NO plays a role in the acquisition of the CTA induced by LiCl. Furthermore, the results suggest that the 5-HT1A receptor plays an important role in the CTA induced by MB and 7-NI, thus indicating a possible interaction between the 5-HT and NO systems.

High-resolution genetic mapping of the saccharin preference locus (Sac) and the putative sweet taste receptor (T1R1) gene (Gpr70) to mouse distal Chromosome 4

The Sac (saccharin preference) locus affecting mouse behavioral and neural responsiveness to sweeteners has been mapped to distal Chr 4. A putative sweet taste receptor, T1R1, has been recently cloned, and the gene encoding it, Gpr70, has also been mapped to mouse distal Chr 4. To assess Gpr70 as a candidate gene for Sac, we compared the Gpr70 sequences of C57BL/6ByJ and 129P3/J mouse strains with different alleles of Sac. Using Gpr70 sequence variation between the C57BL/6ByJ and 129P3/J strains, we conducted a high-resolution analysis of the chromosomal localization of the Gpr70 and Sac loci in the F2 hybrids and 129.B6-Sac partially congenic mice originating from these two strains. The Gpr70 gene maps proximal to Sac, which demonstrates that they are different loci.

Changes of nasal function after temperature-controlled radiofrequency tissue volume reduction for the turbinate

OBJECTIVES

Temperature-controlled and temperature-monitored radiofrequency tissue volume reduction (RFTVR) for the turbinate is a new treatment modality for nasal obstruction secondary to turbinate hypertrophy. We compared the nasal functions after the treatment ofRFTVR and laser vaporizing turbinoplasty (LVT) using subjective symptom scores and objective tests.

STUDY DESIGN

Prospective, randomized clinical trial.

METHODS

Twenty-four patients with nasal obstruction secondary to inferior turbinate hypertrophy were prospectively evaluated from March 1999 to October 1999 at Seoul National University Hospital (Seoul, Korea). Sixteen patients were treated with RFTVR, and eight patients with LVT. The preoperative and postoperative nasal functions were investigated by visual analogue scale of symptoms, butanol threshold test, saccharine test, acoustic rhinometry, rhinomanometry, and ciliary beat frequency.

RESULTS

At 8 weeks postoperatively, the severity and the frequency of nasal obstruction improved subjectively in 81.3% and 93.8% of RFTVR group and in 87.5% and 87.5% of LVT group, respectively. Significant improvement of nasal symptoms began from 2 to 3 days after the operation in the RFTVR group, whereas there was significant improvement of nasal symptoms at 8 weeks after operation in the LVT group. However, objective nasal functions including nasal volume and total nasal resistance were significantly improved at 8 weeks after surgery in both groups. Among patients reporting symptoms of hyposmia, 55.6% of RFTVR group and 63.6% of LVT group showed improved olfaction. Saccharin transit time and ciliary beat frequency were preserved after RFTVR CONCLUSION: RFTVR for the turbinate may be useful as an alternative approach for the treatment of chronic turbinate hypertrophy.