Contributions of taste factors and gender to opioid preference in C57BL and DBA mice (original) (raw)
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Taste reactivity and its modulation by morphine and methamphetamine in C57BL/6 and DBA/2 mice
Physiology & Behavior, 2009
a b s t r a c t C57BL/6J (B6) and DBA2/J (D2) mice differ markedly in voluntary consumption of tastants and responses to abused drugs. In particular, compared to D2 mice, B6 mice avidly drink ethanol and sucrose solutions, but avoid quinine solutions. In the first study, we compared taste reactivity in B6 and D2 mice to determine the extent to which differences in drinking patterns depend on orosensory processing. Both strains showed concentration-dependent increases in positive reactions to sucrose (0.01 to 1 M). Quinine (0.03 to 3 mM) elicited concentration-dependent aversive reactions in B6 mice, whereas all reactions to quinine were virtually indistinguishable from reactions to water in D2 mice. In contrast, D2 mice reacted with relatively strong aversive responses to ethanol (5 to 30%). In the second study, we evaluated the effect of subcutaneous morphine (1 to 4 mg/kg) and methamphetamine (0.5 to 2 mg/kg) on taste reactivity to sucrose. Morphine generally decreased reactions to sucrose in both strains, suggesting a general motor depressant effect. Methamphetamine shifted sucrose responses towards aversion in both strains; particularly in D2 mice. These results suggest that strain-dependent differences in voluntary ethanol and quinine drinking depend at least partially on differences in orosensory responses. However, differences in voluntary sucrose intake may relate solely to genetic differences in post-ingestive factors. Finally, as has been suggested by previous place conditioning studies, methamphetamine appears to induce a dysphoric state in D2 mice, which may be reflected in fewer positive and more negative taste reactions to sucrose in the current study.
A Novel Morphine Drinking Model of Opioid Dependence in Rats
International Journal of Molecular Sciences, 2022
An animal model of voluntary oral morphine consumption would allow for a pre-clinical evaluation of new treatments aimed at reducing opioid intake in humans. However, the main limitation of oral morphine consumption in rodents is its bitter taste, which is strongly aversive. Taste aversion is often overcome by the use of adulterants, such as sweeteners, to conceal morphine taste or bitterants in the alternative bottle to equalize aversion. However, the adulterants’ presence is the cause for consumption choice and, upon removal, the preference for morphine is not preserved. Thus, current animal models are not suitable to study treatments aimed at reducing consumption elicited by morphine itself. Since taste preference is a learned behavior, just-weaned rats were trained to accept a bitter taste, adding the bitterant quinine to their drinking water for one week. The latter was followed by allowing the choice of quinine or morphine (0.15 mg/mL) solutions for two weeks. Then, quinine wa...
Opioid mediation of starch and sugar preference in the rat
Pharmacology, biochemistry, and behavior, 2010
In our prior studies, administration of the opioid receptor antagonist naltrexone did not block conditioned preferences for a flavor paired with a preferred sugar solution over a flavor paired with saccharin. This may be because both training solutions were sweet, and their attractiveness was reduced by naltrexone. The present study compared the effects of naltrexone on preferences for flavors paired with sugar or starch drinks that have distinctive tastes to rats. Experiment 1 assessed naltrexone's effect on the preference for unflavored 8% cornstarch and 8% sucrose aqueous solutions/suspensions. The food-restricted rats displayed a significant sucrose preference which increased following systemic treatment with naltrexone (1 or 3mg/kg) even though total intake of both solutions declined. In Experiment 2, rats were trained to drink flavored (cherry or grape) starch and sucrose solutions in separate one-bottle sessions. In a two-bottle choice test with both flavors presented in...
Developmental Psychobiology, 2013
The present report asked if the previously reported differences in morphine-induced conditioned taste avoidance between adult F344 and LEW rats (F344 > LEW) are also evident in prepubescence (early adolescence). To assess this possibility, adult (Experiment 1) and prepubertal (Experiment 2) F344 and LEW rats were assessed for their ability to acquire morphine-induced taste avoidance (0, 3.2, 10, or 18 mg/kg) in a modified taste avoidance procedure. In each experiment, rats of both strains were given repeated pairings of saccharin and morphine followed by a final two-bottle avoidance test. Adult and prepubertal F344 subjects displayed a more rapid acquisition of the avoidance response as well as stronger suppression of consumption than their LEW counterparts. These data suggest the strains differ in their sensitivity to the aversive effects of morphine and that this differential sensitivity is evident early in development and is developmentally stable. The basis for these strain differences in morphine-induced avoidance was discussed. ß 2013 Wiley Periodicals, Inc. Dev Psychobiol 56: 979-988, 2014.
Pharmacology Biochemistry and Behavior, 2010
In our prior studies, systemic administration of the opioid receptor antagonist naltrexone (NTX) did not block flavor preference conditioning by the sweet taste or post-oral actions of sugar despite reducing intake. Because opioid signaling in the nucleus accumbens (NAc) is implicated in food reward, this study determined if NTX administered into the NAc would block the expression of sugar-conditioned preferences. In Experiment 1, food-restricted rats with bilateral NAc shell or core cannulae were trained to drink a fructose (8%) + saccharin (0.2%) solution mixed with one flavor (CS+) and a less-preferred 0.2% saccharin solution mixed with another flavor (CS−) during one-bottle sessions. Two-bottle tests with the two flavors mixed in saccharin solutions occurred 10 min following total bilateral NAc shell or core doses of 0, 1, 25 and 50 μg of NTX. The rats preferred the CS+ over CS− following vehicle (80%) and all NTX doses in the shell and core. The CS+ preference was reduced to 64% and 72% by 50 μg NTX in the shell and core, although only the core effect was significant. In Experiment 2, food-restricted rats were trained to drink one flavored saccharin solution (CS+) paired with an intragastic (IG) glucose (8%) infusion and a second flavored saccharin solution (CS−) paired with an IG water infusion. In subsequent two-bottle tests, the rats displayed significant preferences for the CS+ (81-91%) that were unaltered by any NTX dose in the shell or core. CS+ intake, however, was reduced by NTX in the shell, but not the core. These data indicate that accumbal opioid antagonism slightly attenuated, but did not block the expression of sugar-conditioned flavor preferences. Therefore, while opioid drugs can have potent effects on sugar intake they appear less effective in altering sugar-conditioned flavor preferences.
Sweet taste pleasantness is modulated by morphine and naltrexone
Psychopharmacology, 2016
BackgroundRodent models highlight the key role of μ-opioid receptor (MOR) signaling in palatable food consumption. In humans, however, the effects of MOR stimulation on eating and food liking remain unclear.ObjectivesHere, we tested sweet pleasantness experience in humans following MOR drug manipulations. We hypothesized that behaviors regulated by the endogenous MOR system would be enhanced by MOR agonism and decreased by antagonism. In line with rodent findings, we expected the strongest drug effects for the sweetest (high-calorie) sucrose stimuli. As very sweet stimuli are considered aversive by many people (called sweet dislikers), we also assessed whether MOR manipulations affect pleasantness ratings of sucrose-water stimuli differently depending on subjective and objective value.MethodsIn a bidirectional psychopharmacological cross-over study, 49 healthy men underwent a sweet taste paradigm following double-blind administration of the MOR agonist morphine, placebo, and the opi...
Pre-exposure to morphine and the attenuation of conditioned taste aversion in rats
Pharmacology Biochemistry and Behavior, 1978
IO morphine and the utrenucrtion of conditioned tavre crwrsion in rats. PHARMAC. BIOCHEM. BEHAV. 9(5) 639-645, 1978.-Three experiments were done using male Wistar rats to determine whether the mechanisms underlying the attenuation of a conditioned taste aversion to morphine by pre-exposure to the drug were similar to those involved in the development of tolerance to the analgesic response to morphine. This was tested by determining whether the effect of pre-exposure on conditioned taste aversion was situation-specific. In Experiment 1 it was found that having different environments for the pre-exposure injections and for the conditioning injections of morphine had no effect on the attenuation of the taste aversion. This finding was replicated in Experiment 2 in which it was also found that the attenuation of the analgesic effect, tested for in the same animals, was specific to the environment in which repeated injections were given. It was concluded that the attenuation of conditioned taste aversion involved processes different from those responsible for the attenuation of the analgesic effect of morphine. Experiment 3 showed that pairing the pre-exposure injections of morphine with one distinctive taste stimulus prevented the attenuation of the conditioned taste aversion to a second taste stimulus. These results suggest that different associative processes are responsible for the two types of attenuation.
Taste function in methadone-maintained opioid-dependent men
Drug and Alcohol Dependence, 2002
It has been shown repeatedly that opioid dependence is associated with increased consumption of refined sugars. It is possible that this association results from altered taste reactivity in opioid-dependent subjects. Thus, in the present study, we compared taste responses to sweet, bitter, sour and salty solutions in methadone-maintained opioid-dependent men and healthy control subjects. The two groups did not differ in terms of rated intensity or pleasantness of sucrose (1 Á/30%), quinine (0.001 Á/0.005%), citric acid (0.02 Á/0.1%) and sodium chloride (0.18 Á/0.9%) solutions. Proportions of 'sweet-likers', i.e. subjects rating a 30% sucrose (0.88 M) solution as the most pleasant, were also similar in both groups. In line with the previous findings, the methadone-maintained subjects reported adding more table sugar to caffeinated beverages. The results of the present study suggest that changes in taste reactivity may not be responsible for altered dietary choices in opioid addicts. #