Voluntary ethanol consumption changes anticipatory ultrasonic vocalizations but not novelty response

Abstract

Novelty and sensation seeking (NSS) and affective disorders are correlated with earlier ethanol (ETOH) consumption, and sustained drinking into adulthood. Understanding the NSS response and affective response before and after voluntary ETOH consumption could elucidate important individual differences promoting sustained ETOH consumption. This study determined that NSS and affective response to rewarding stimulation—measured by ultrasonic vocalizations (USVs)—change after adolescent ETOH voluntary drinking. Rats were tested for their NSS response using the inescapable novelty test. Then rats were tested for their affective response to a natural reward and USVs were measured. The natural reward was experimenter-induced play behavior. Rats were exposed to ETOH for 8 weeks using an intermittent two bottle paradigm. After 8 weeks of voluntary consumption, rats were retested for their response to NSS and affective response to natural reward. Results indicate that voluntary ETOH consumption did not change the response to novelty. Control and ETOH exposed rats decreased their novelty response equally after ETOH consumption, suggesting the decrease was due to age. Importantly, voluntary ETOH consumption changed affective USVs. Compared to water-drinking control rats, ETOH-consuming rats elicited greater anticipatory trill USVs to a natural reward-associated context during a post-drinking probe test. Tickle-induced trill USVs did not change differently between ETOH and control rats. These results provide evidence that voluntary intermittent ETOH exposure increases the anticipation of reward and may represent a form of incentive salience. We postulate these diverging effects could be due to differences in incentive salience or reward processing. Together, these results suggest that voluntary ETOH consumption changes the affective response to conditioned and unconditioned natural rewards and offers a behavioral mechanism for studying affective reward processing after ETOH consumption.

Investigating social housing: The effects of isolation on rodent ethanol consumption

“…The drinking female rats appeared to show greater rearing activity after the midway point of each trial compared to the control female rats (as opposed to the male rats which were roughly equal in both before/after rearing counts in both drinking conditions). Previous literature (conducted using males) suggests that chronic consumption of ethanol has a dampening and depressive effect on anticipation (Garcia et al, 2017), and instead we found the opposite, using females. Again, this is concerning, considering each of the studies cited above that found significant differences between drinkers and non-drinkers in perceived anxiety (Garcia et al, 2017;Izídio & Ramos, 2007;Santucci et al, 2008) used the IATBCP procedure, or some variation of it.…”

“…Previous literature (conducted using males) suggests that chronic consumption of ethanol has a dampening and depressive effect on anticipation (Garcia et al, 2017), and instead we found the opposite, using females. Again, this is concerning, considering each of the studies cited above that found significant differences between drinkers and non-drinkers in perceived anxiety (Garcia et al, 2017;Izídio & Ramos, 2007;Santucci et al, 2008) used the IATBCP procedure, or some variation of it. It may well be that methodological differences (such as the age of the animals and different experimental procedures used) contributed to this contradiction.…”

“…Another study found that rats isolated throughout adolescence consumed more ethanol than group-housed rats, and displayed more anxious behaviours, and less fear extinction (Skelly et al, 2015). When analysed without taking housing into consideration, chronic voluntary ethanol consumption has been found to increase state anxiety, both neurochemically and behaviourally (Izídio & Ramos, 2007;Santucci et al, 2008), and reduce anticipatory behaviours such as USVs when given rewardlearning tasks (Garcia et al, 2017).…”