The effects of restraint stress on voluntary ethanol consumption in rats.

Sixty Wistar rats (Rattus norvegicus) were assigned to 4 groups of 15 rats each: ethanol stress (ES), ethanol no-stress (EN), isocaloric stress (IS) and isocaloric no-stress (IN). The effect of restraint stress on daily intake of ethanol and a 0.72% solution of glucose was examined in an ABA design (stress-no stress-stress). During the stress phases, 2 groups were subjected to daily 15-min restraint stress, whereas 2 groups were placed in different cages for 15 min as a control. All 4 groups were then given 6-hr access to their assigned liquid alone for 4 days followed by a choice between their assigned liquid and water on the 5th day. The ES group significantly increased their ethanol intake (g/kg) compared to the EN group on choice days but not on forced days. Percentage preference for ethanol was significantly greater and increased at a faster rate over the 75-day testing period compared with the EN group. However, total ethanol consumption (g/kg) and percentage preference did not vary as a function of phase. It is notable that the effects of restraint stress on ethanol self-administration persisted even after the stress schedule was removed.

Concurrent self-administration of ethanol and an alternative nondrug reinforcer in monkeys: effects of income (session length) on demand for drug.

Eight rhesus monkeys (Macaca mulata) were trained to self-administer orally delivered ethanol (8%) and saccharin (0.03 or 0.3% wt/vol) or water under concurrent fixed-ratio (FR) schedules. The FR requirement for saccharin was fixed at 32, while the FR for ethanol was varied (4, 8, 16, 32, 64 and 128) in a non-systematic order to assess demand for drug. Demand was defined as consumption plotted as a function of price (FR). Income was defined as the duration of access to available resources. Income was varied by allowing access to the concurrently available liquids 20, 60 or 180 min per day. Order of testing was counter-balanced across monkeys. Saccharin deliveries were much higher than ethanol deliveries under the 180-min income condition; however, they were lower than ethanol deliveries when income was reduced to 20 min and the ethanol FR was 4, 8 or 16. Thus, when the price of drug was relatively low, consumption of drug exceeded that of the nondrug reinforcer, and that relationship was reversed as income decreased. Saccharin deliveries sustained a proportionally greater reduction due to decreased income compared to ethanol deliveries. As income decreased from 180 to 20 min, saccharin deliveries were reduced by an average of 79.1% (across ethanol FR conditions) while ethanol deliveries were reduced by an average of 41.2 and 40.8% when concurrent saccharin or water were available, respectively; thus, drug self-administration was more resistant to income changes than saccharin. The demand for ethanol was shifted downward in a parallel fashion as income decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of prior dominance or subordination experience on conspecific odor preferences in mice.

Preferences for the soiled bedding odors of familiar and unfamiliar conspecifics were assessed among male mice rendered dominant or subordinate by a series of resident-intruder encounters. Alpha males preferred the odors of their familiar antagonist most strongly. Subordinates, in contrast, showed strongest preferences for unfamiliar females and a weaker preference for alpha odors. When female odors were eliminated from the preference test, alphas continued to show the strongest preference for familiar subordinate odors while subordinates displayed roughly equivalent preference for the odors of familiar alphas and unfamiliar males. It is suggested that the apparent mild preferences of subordinates for dominant conspecific odors reflects fear motivated risk assessment. In contrast, approaches of dominants to subordinate odors seems to be appetitively motivated. Generally recognizable subordination odors may be useful to unfamiliar males in recognizing exploitable resources.

Test-specific effects of FG-7142 on isolation-induced aggression in mice.

Treatment with FG-7142 decreased isolation-induced attack, but not defense, by male mice when the residents' home cages contained only a sawdust substrate. When a small wooden nesting box was added to the cage (Experiment 2), however, FG-7142 somewhat increased levels of attack. Time spent in the nesting box was also increased, while overall levels of social interaction were decreased, by drug treatment in Experiment 2. The latter findings are consistent with FG-7142's well-documented anxiogenic properties and indicate that this drug is probably proaggressive in its actions. The antiaggressive effects of FG-7142 in Experiment 1 may have resulted from drug-induced fear behaviors that were incompatible with attack. Alternatively, Experiment 2 suggests the possibility that species-typical attack may be defensively motivated under some circumstances. Although the antiagressive properties of eltoprazine and yohimbine were unaffected by the addition of the nest box (Experiment 3), the provision of some sort of refuge within the testing apparatus may be an important methodological consideration for studies employing resident-intruder paradigms.

Effects of eltoprazine hydrochloride on reactivity to conspecific or novel odors and activity.

Treatment with eltoprazine (DU 28853) increased the number of entries by male mice into compartments containing the odors of male and female conspecifics. This effect was most pronounced when odors were provided by previously defeated males. In contrast, the drug had no effect upon responsiveness to the odors of cinnamon and chocolate. The results suggest that eltoprazine may selectively increase reactivity to conspecific odors and that this effect is further enhanced by agonistic experience. Eltoprazine also substantially increased activity levels in all experiments. Since hyperactivity occurred both in the presence and absence of conspecific odors, however, the drug's effects on activity and olfaction seem to be largely independent. The results suggest that the aggression-modulating effects of eltoprazine, as well as other drugs, may be mediated in part by their effects on normal olfactory function.

Effects of yohimbine on isolation-induced aggression, social attraction, and conspecific odor preference in mice.

Yohimbine treatment inhibited isolation-induced attack in mice but had no effect on defense. The drug also increased social distances and produced a transient decrease in preference for conspecific male odors. The antiaggressive actions of yohimbine parallel those reported for the anxiogenic beta-carbolines and for phenylpiperazine "serenic" agents. The results emphasize the importance of supplementing conspecific agonistic encounters with additional behavioral measures such as nonagonistic social attraction in evaluating antiaggressive drugs. The decreased responsiveness to conspecific odors seen in Experiment 3 also suggests that increased conspecific avoidance may be mediated, in part at least, by altered olfactory processes.

Effects of eltoprazine hydrochloride on exploratory behavior and social attraction in mice.

The effects of eltoprazine (DU 28853) on exploratory behavior and conspecific social attraction were examined in four experiments. Drug treatments somewhat enhanced three forms of exploratory behavior but decreased social attraction. The results indicate that eltoprazine, in sharp contrast to fluprazine, weakly ameliorates neophobic responses. Both eltoprazine and fluprazine seem to increase the aversiveness of encounters with other organisms, however. The latter effects may be mediated, in part at least, by some alteration in olfactory function.