skip to main content


Title: Shortening time for access to alcohol drives up front-loading behavior, bringing consumption in male rats to the level of females
Abstract Background

Incentives to promote drinking (“happy hour”) can encourage faster rates of alcohol consumption, especially in women. Sex differences in drinking dynamics may underlie differential health vulnerabilities relating to alcohol in women versus men. Herein, we used operant procedures to model the happy hour effect and gain insight into the alcohol drinking dynamics of male and female rats.

Methods

Adult male and female Wistar rats underwent operant training to promote voluntary drinking of 10% (w/v) alcohol (8 rats/sex). We tested how drinking patterns changed after manipulating the effort required for alcohol (fixed ratio, FR), as well as the length of time in which rats had access to alcohol (self-administration session length). Rats were tested twice within the 12 h of the dark cycle, first at 2 h (early phase of the dark cycle, “early sessions”) and then again at 10 h into the dark cycle (late phase of the dark cycle, “late sessions”) with an 8-h break between the two sessions in the home cage.

Results

Adult females consumed significantly more alcohol (g/kg) than males in the 30-min sessions with the FR1 schedule of reinforcement when tested late in the dark cycle. Front-loading of alcohol was the primary factor driving higher consumption in females. Changing the schedule of reinforcement from FR1 to FR3 reduced total consumption. Notably, this manipulation had minimal effect on front-loading behavior in females, whereas front-loading behavior was significantly reduced in males when more effort was required to access alcohol. Compressing drinking access to 15 min to model a happy hour drove up front-loading behavior, generating alcohol drinking patterns in males that were similar to patterns in females (faster drinking and higher intake).

Conclusions

This strategy could be useful for exploring sex differences in the neural mechanisms underlying alcohol drinking and related health vulnerabilities. Our findings also highlight the importance of the time of testing for detecting sex differences in drinking behavior.

 
more » « less
NSF-PAR ID:
10306735
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Springer Science + Business Media
Date Published:
Journal Name:
Biology of Sex Differences
Volume:
12
Issue:
1
ISSN:
2042-6410
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract Objective

    To identify ketamine's dosing schedule that ameliorates voluntary food restriction, hyperactivity and body weight loss of adult mice undergoing activity‐based anorexia (ABA), an animal model of anorexia nervosa.

    Method

    Female and male C57BL6 mice underwent three cycles of ABA, starting from mid‐adolescence. ABA vulnerability was compared within and across two groups of animals: those injected intraperitoneally with 30 mg/kg ketamine for three consecutive days (30mgKetx3) during the second ABA in late adolescence (ABA2) or with vehicle only (Vx3).

    Results

    Vx3 females and males exhibited individual differences in wheel running and weight retention during first ABA in mid‐adolescence (ABA1), ABA2, and third ABA in adulthood (ABA3). Their wheel running correlated with anxiety‐like behavior. During ABA1 and ABA3, weight gain of Vx3 females (but not males) after food consumption correlated negatively with food‐anticipatory activity (FAA) preceding the feeding hours, indicating that females with higher levels of running restrict feeding more and persistently. This paradoxical relationship confirms earlier findings of ABA females without ketamine treatment, capturing the maladaptive behaviors exhibited by individuals diagnosed with anorexia nervosa. By contrast, 30mgKetx3 had an effect on both sexes of reducing hyperactivity during the feeding hours acutely and reducing anxiety‐like behavior's contribution to running. For females, only, 30mgKetx3 acutely improved the extent of compensatory food consumption relative to FAA and improved weight retention during ABA3, 12 days post ketamine in adulthood.

    Discussion

    Sub‐anesthetic ketamine evokes behavior‐specific ameliorative effects for adult mice re‐experiencing ABA, supporting the notion that multiple doses of ketamine may be helpful in reducing relapse among adults with anorexia nervosa.

    Public Significance Statement

    This study examined whether ketamine reduces anorexia‐like behaviors in adult mice. Three daily sub‐anesthetic ketamine injections suppress wheel running during and leading up to the hours of food availability and enable animals to compensate better for weight loss associated with excessive exercise by eating more. These findings suggest that ketamine may help adult females diagnosed with anorexia nervosa but also point to sex‐ and age‐related differences in the action of ketamine.

     
    more » « less
  2. Background

    Aversion to the orosensory properties of concentrated ethanol (EtOH) solutions is often cited as a primary barrier to initiation of drinking and may contribute to abstention. These aversive properties include gustatory processes which encompass both bitter‐like taste qualities and trigeminal‐mediated irritation. Chronic intermittent EtOH access (CIA) results in substantial and persistent increases in EtOH consumption, but the degree to which this facilitation involves sensory responding to EtOH and other bitter stimuli is currently undetermined.

    Methods

    Long‐Evans rats were given brief‐access licking tests designed to examine the immediate, taste‐guided assessment of the palatability of EtOH and quinine solutions. Rats were assessed once in a naïve state and again following previous brief‐access exposure, or following 4 weeks ofCIA. The relationship between the sensitivity to the aversive orosensory properties of EtOH and quinine following EtOH access and the impact of antecedent quinine exposure on the acceptance of EtOH were determined in 2 parallel studies.

    Results

    Both brief access to EtOH and 4‐weekCIAresulted in substantial rightward shifts in the concentration–response function of brief‐access EtOH licking, indicating that EtOH exposure increased acceptance of the taste of EtOH. The initial sensitivity to the aversive orosensory properties of EtOH and quinine was positively correlated in naïve rats, such that rats that were initially more accepting of quinine were also more accepting of EtOH. Rats that sampled quinine immediately prior to tasting EtOH exhibited successive positive contrast in that they were more accepting of highly concentrated EtOH, relative to a water‐control group.

    Conclusions

    Increased EtOH acceptance following exposure is, at least in part, facilitated by a decrease in its aversive sensory properties. Both long‐ and short‐term access increase the palatability of the taste of EtOH in brief‐access licking tests. Moreover, the sensitivity to the bitterness of quinine was predictive of acceptance of EtOH indicating some commonality in the sensory mechanisms that mediate the initial acceptance of the 2 stimuli. Accordingly, immediate prior exposure to quinine results in increased acceptance of EtOH, suggesting that successive positive contrast between oral stimuli may contribute to increased alcohol consumption.

     
    more » « less
  3. Abstract

    Animals capable of rapid (i.e., physiological) body color change may use color to respond quickly to changing social or physical environments. Because males and females often differ in their environments, the sexes may use changes in body color differently, reflecting sexual dimorphism in ecological, behavioral, or morphological traits. Green anole lizards,Anolis carolinensis, frequently switch their dorsal body color between bright green and dark brown, a change that requires only seconds, but little is known regarding sexual dimorphism in their color change. We tested three hypotheses for the function of body color (thermoregulation, camouflage via background-matching, and social communication) to determine the ecological role(s) of physiological color change in anoles. First, we examined instantaneous body color to determine relationships between body color and body temperature, substrate color and type, and whether these varied between the sexes. Next, we examined the association between color change and behavioral displays. Altogether, we found that males were more likely to be green than females, and larger lizards were more often green than smaller ones, but there was no evidence that anole body color was associated with body temperature or background color during the summer breeding season. Instead, our results show that although the sexes change their color at approximately the same rates, males changed color more frequently during social displays, while females remained green when displaying. In sum, social communication appears to be the primary function of anole color change, although the functions of body color may differ in the nonbreeding season.

    Significance statement

    Many animals can change their body color in response to their environments, and in many species, males and females experience different environments. In this study, we examined whether the sexes of green anole lizards use the ability to rapidly change their body color between green and brown for different functions. We found that, when a lizard was first sighted, its body color did not appear to match its background color in either sex (suggesting that color change does not contribute to avoidance of detection by potential predators), and body color was not associated with temperature for either sex (i.e., color was unlikely to influence body temperature). Yet, males changed color more often when performing social displays to other lizards, while females remained green during social displays. Thus, rapid color change plays an important role in social communication in both sexes, highlighting how males and females may use the same behavior to convey different messages.

     
    more » « less
  4. Background and Purpose

    Females are more sensitive than males to both the acute and prolonged effects of psychomotor stimulants. In females, this is regulated by oestradiol, which enhances dopamine release in the dorsal striatum. In this study, we tested the acute effect of oestradiol on dopamine release in the nucleus accumbens (NAc) shell after cocaine administration and investigated which oestradiol receptors (ERs) contribute to sex differences in the response to cocaine.

    Experimental Approach

    The ability of oestradiol benzoate (EB) to acutely modulate the effect of cocaine on phasic dopamine release in the NAc shell was measured by fast‐scan cyclic voltammetry in anaesthetized male and female rats. The roles of ER subtypes, ERα and ERβ, was determined with selective agonists.

    Key Results

    EB acutely enhanced the effect of cocaine on stimulated dopamine release from the NAc shell in females but not in male rats only at levels of stimulation expected to optimally saturate dopamine transporters. Enhanced dopamine release after cocaine administration was also observed in females after selective activation of ERβ but not ERα. EB attenuated the effect of cocaine on NAc shell dopamine reuptake in males but not in females.

    Conclusions and Implications

    Oestradiol acutely and rapidly regulates dopamine release in females and dopamine reuptake in males. In females, oestradiol rapidly enhances the effect of cocaine on dopamine release, likelyviaactivation of ERβ. The effect of oestradiol in males is not seen with selective receptor subtype activation, a topic deserving of further study.

    LINKED ARTICLES

    This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visithttp://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc

     
    more » « less
  5. Abstract Objectives

    Sodium, a vital micronutrient that is often in scarce supply for tropical herbivores, is sometimes found at high concentration in decaying wood. We tested two hypotheses for chimpanzees: first, that wood‐eating facilitates acquisition of sodium; second, that wood‐eating occurs in response to the low availability of sodium from other dietary sources.

    Materials and Methods

    We studied the behavior of more than 50 chimpanzees of all age‐sex classes in the Kanyawara community of Kibale National Park, Uganda. We quantified the sodium content of dietary items, including wood samples from tree species that chimpanzees consumed or did not consume. To assess variation in sodium intake, we used 7 years of data on time spent feeding on plant foods, 18 months of data on rates of food intake by adult females, and 20 years of data on meat‐eating.

    Results

    Major dietary sources of sodium were wood, fruits and meat. Chimpanzees consumed wood primarily from decaying trees ofNeoboutonia macrocalyx(Euphorbiaceae), which had substantially higher sodium content than all other dietary items tested. Wood‐eating was negatively correlated with fruit‐eating. Females ate wood more often than males, while males had a greater probability of consuming meat at predation events.

    Discussion

    We propose that females ate wood more often than males because females had reduced access to meat, their preferred source of sodium. This hypothesis suggests that the need for sodium is a motivating reason for chimpanzees to consume both meat and wood.

     
    more » « less