Some determinants of a natural food aversion in Norway rats.

Adult male Long-Evans rats were permitted to feed on the carcasses of adult male rodents, freshly sacrificed by CO? asphyxiation. In a 2-choice preference test (Exp I), hungry Ss were offered 1 conspecific and 1 house mouse, the pair of carcasses being either intact or skinned. 18 Ss offered intact carcasses fed on the mouse or on neither carcass, but 18 Ss offered skinned carcasses fed indiscriminately, usually on both carcasses. In Exp II, 10 hungry Ss that earlier had observed a cagemate feeding on intact conspecific carcasses fed more readily on a similar carcass during a single-choice test than did 8 controls. In Exp II, 20 food-deprived Ss (96 hrs) fed more readily and consumed more tissue from an intact conspecific carcass than did 20 nondeprived Ss. It is concluded that the aversion to feeding on the intact carcass of a freshly sacrificed adult conspecific is deprivation dependent and is mediated by chemoreceptive stimuli from the skin and/or fur. The aversion is diminished by social facilitation. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of a natural food aversion in domestic rats (Rattus norvegicus) and house mice (Mus musculus).

During a 1-hr feeding test, 34 hungry male Long-Evans rats that had been reared individually from weaning with a Swiss Webster house mouse were less likely to feed on the intact carcass of a freshly sacrificed mouse than were 39 rats that had been reared individually with another rat. Likewise, 42 hungry mice that had been reared individually with a rat were less likely to feed on a dead rat than were 29 mice that had been reared individually with another mouse. Regardless of the social conditions during rearing, hungry mice were more likely to feed on a dead mouse than were hungry rats to feed on a dead rat. Findings suggest that the tendency by rats to reject conspecific flesh stems, at least in part, from prior experience with conspecifics and with their own bodies. The experiential factors mediating the tendency by mice to reject conspecific flesh remain unclear. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of photoperiod and social environment on sexual maturation in female deer mice (Peromyscus maniculatus bairdii).

Tested the reproductive response of young female deer mice to either a long or short photoperiod combined with the presence of adult males, adult females, or social isolation. 266 Ss were reared on either a long photoperiod (15 hrs light, 9 hrs dark) or on short days (8 hrs light, 16 hrs dark) from birth. Beginning at weaning, females were housed with an adult male, with an adult female, or in social isolation. In Exp I, vaginas opened more slowly in Ss on short days than in those on long days. Vaginal introitus was also retarded in Ss reared with an adult female in comparison with Ss reared in isolation. When examined at 37 days of age, Ss reared with an adult male had larger uteri than those reared alone; uteri were also larger in long-day than in short-day Ss. In Exp II, Ss were killed at 30 days of age; again, uterine growth was stimulated by exposure to either long days or an adult male. As was previously demonstrated for male deer mice, sexual maturation in females is regulated by photoperiod and social cues. Heterospecific social stimuli accelerate maturation in individuals that otherwise would be inhibited by having been reared on a short photoperiod. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition and extended retention of a conditioned taste aversion in preweanling rats.

Four experiments employed a taste aversion conditioning procedure appropriate for both neonatal and adult rats to investigate the ontogeny of extended retention. In Exp I, 200 outbred albino rats trained at 1, 10, 20, or 60 days of age were tested for retention of the taste aversion 25 days later. At testing, only those Ss conditioned when 20 or 60 days old demonstrated significant taste aversions. Exps II and III, with 190 Ss, established that Ss 14–25 days old and older were able to retain significant taste aversions following a 25-day retention interval. 80 younger Ss did, however, acquire and retain the aversion for several days and showed a gradual retention loss over progressively longer retention intervals (Exp IV). Findings suggest that preweanling rats demonstrate initial consolidation, storage, and retrieval of conditioned taste aversions. It is only after this initial period that retention deficits become evident. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The opioid/nonopioid nature of stress-induced analgesia and learned helplessness.

Investigated whether the same factors that activate the processes that produce escape interference might also activate processes leading to opioid stress-induced analgesia (SIA). Exposure to a variety of stressors produces a subsequent analgesic reaction that is sometimes opioid in nature (reversed by opiate antagonists and cross-tolerant with morphine) and sometimes nonopioid. In Exp I, 40 male albino rats were subjected to 20 min of intermittent footshock, 3 min of continuous footshock, tailshock on a VI schedule, or confinement only. Ss were given escape/avoidance training 24 hrs later. In Exp II, 36 Ss received SIA with a tail-flick apparatus. In Exp III, 40 Ss received inescapable tailshocks or confinement only. In Exp IV, 24 Ss received 2 sessions of footshock before tail-flick was assessed. Both of the opioids SIA procedures produced a learned helplessness effect as assessed by shuttlebox escape acquisition and an analgesia that was reinstatable 24 hrs later. The nonopioid procedures produced neither a learned helplessness effect nor a reinstatable analgesia. These data implicate the learning of uncontrollability in the activation of opioid systems. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fear and affiliation in domesticated male rats.

Male rats actively seek the opportunity to interact with other male rats. Three experiments with 208 Long-Evans males examined the hypothesis that the presence of conspecifics can reduce the behavioral signs of fear and that this capacity provides part of the attraction to conspecifics. In Exp I, the immobility response was measured following exposure to a stressful noise. Ss that were observed in groups exhibited shorter durations of immobility than those observed alone. The "group" effect was sufficiently powerful to nullify different housing conditions and different degrees of familiarity among the Ss. Exp II compared social and nonsocial stimuli and found that only the former effectively reduced the immobility response. In Exp III, stressed Ss were more likely to choose to interact with a conspecific in a T-maze than were nonstressed Ss. Again, rearing conditions made little difference; both individually and group housed Ss were highly attracted to a conspecific. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned aversion to distinct environmental stimuli resulting from gastrointestinal distress.

In Exp I, 40 male Sprague-Dawley-derived rats subjected to apomorphine-induced malaise following a 2-min placement in a black compartment avoided this black compartment significantly more than 10 controls in a choice situation. The degree of aversion, however, was substantially reduced when Ss were provided water (or saccharin) in the black compartment during conditioning and testing. Ss learned to suppress consumption of fluid in the black compartment. In Exp II, 10 Ss were made ill in the black compartment. Later, when drinking saccharin (or saline) preceded placement in the black compartment, Ss learned to suppress consumption of that fluid. The black compartment had become a conditioned reinforcer for taste aversion. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned aversions to copulatory behaviors in male rats.

Used LiCl for an aversive effect on copulatory behavior in adult experienced and inexperienced male hooded rats (Exp I) and in inexperienced adult male Holtzman rats (Exp II). When males received an injection of LiCl immediately after an encounter with an estrous female, the vigor of subsequent copulatory responding was initially unaffected. After 5–20 such pairings, however, males displayed an aversion to copulatory behaviors; they ceased to copulate entirely. These aversions persisted when Ss were tested in a novel environment and extinguished after 4 nonreinforced trials. This multiple-trial adaptation of the conditioned taste aversion paradigm provides a new approach to the aversive control of sexual behavior. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fighting in juvenile rats and the ontogeny of agonistic behavior.

Studied the intraspecific interactions of 160 male Long-Evans domesticated rats in 2 experiments to examine the relation between juvenile and adult fighting. Ss were observed throughout their ontogeny and after they reached sexual maturity. In Exp I, Ss were group housed with siblings and observed with siblings. Ss in Exp II were in 1 of 4 conditions that were either group or individually housed and were observed with either familiar or unfamilar conspecifics. Data suggest that the individual differences of juveniles remained reasonably stable throughout Ss' ontogeny and into adulthood. The conclusion is that the relative frequencies of these immature fights can predict the future aggressiveness of an animal as an adult. Moreover, the factors that influence adult aggressive behaviors, factors such as unfamiliarity and social deprivation, also have an impact on juvenile agonistic behaviors. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thiamin deprivation in ventromedial hypothalamic hyperphagic rats: Anorexia, specificity of food aversion, and a dietary consideration.

In 3 studies, the anorexic consequence of thiamine deprivation was investigated in ventromedial hypothalamic (VMH) hyperphagic CD male rats under either high-fat or low-fat (HF and LF, respectively) thiamine-free diet conditions. The LF diet maintained feeding significantly longer in thiamine-deprived VMH Ss than in intact Ss, whereas the HF diet sustained feeding in thiamine-deficient intact Ss and accelerated anorexia onset in vitamin-B1-deprived VMH Ss. This effect was noted under both ad lib and pair-feeding conditions. Thiamine-deprived VMH Ss subjected to weight control developed anorexia sooner than intact Ss regardless of the diet employed. The VMH Ss fed an HF diet failed to resume feeding after thiamine readministration, which is interpreted as a permanent aversion to this diet. The relation between dietary intake and conditioned taste aversion is discussed with reference to the VMH and intact rats. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ACTH and ACTH4–20 modification of neophobia and taste aversion responses in the rat.

A series of 6 experiments assessed the effects of ACTH and the ACTH analog ACTH4–20 on drinking in conditioned taste aversion and neophobic situations using a total of 168 male Sprague-Dawley rats as Ss. Both substances delayed the extinction of a conditioned taste aversion established by a single pairing of lithium chloride with milk (Exp I). However, in this situation, the ACTH parent peptide was more potent behaviorally. ACTH supressed milk consumption in Ss with no toxicosis experience (Exp II). This effect was apparently not due to the conditioning of a taste aversion (Exp III) with ACTH serving as a weak aversive UCS. Exogenous ACTH (Exp IV) or ACTH4–20 (Exp V) did not enhance neophobia; however, repeated injections of ACTH suppressed drinking. This ACTH suppression was related to the familiarity/novelty of the substance being consumed. The neophobic response to milk was not accompanied by pituitary-adrenal activation (Exp VI). Both neophobic and conditioned taste aversion situations appear to be useful for assessing peptide effects on consummatory behavior. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned taste aversions and neophobia in rats with hippocampal lesions.

In Exp I extensive hippocampal lesions retarded, but did not prohibit, the conditioning of a strong taste aversion to physiological saline (the CS) in 16 male Holtzman albino rats when illness (the UCS) was induced by apomorphine injection 15 min following ingestion of the saline. In Exp II hippocampal lesions reduced the aversiveness of novelty in a drinking fluid for 21 thirsty Ss. It is suggested that the mild impairment of taste aversion learning in Ss with hippocampal lesions was not the result of destruction of mnemonic mechanisms that serve to span the long CS-UCS interval but rather that the reduced intensity of the aversion resulted from a lesion-altered neophobic disposition that weakened the saliency of the novel flavor CS. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemosensory and hormonal mediation of social memory in male rats.

The persistence with which 12 intact and 12 castrated adult male Holtzman rats investigated a juvenile conspecific was reduced following preexposure to either the juvenile or chemosensory stimuli (soiled bedding or urine) from that juvenile, which suggests the presence of a chemosensorily mediated social memory. Any such memory may have adaptive value in that it permits a more ready identification of novel conspecifics. Persistence of social investigatory behavior in castrated Ss demonstrates the importance of male gonadal hormones in the chemosensorily mediated social memory. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sodium homeostasis in chronic decerebrate rats.

Two experiments examined physiological and behavioral concomitants of sodium need in supracollicularly transected and pair-fed intact male Sprague-Dawley rats. Chronic decerebrate Ss, like intact Ss, reduced their urine sodium output when placed on a sodium-deficient diet. Similarly, 24 hrs after sodium loading, decerebrate and intact Ss excreted comparable levels of the excess sodium. In the 2 hrs immediately following loading, decerebrate Ss excreted less sodium. In contrast, behavioral aspects of sodium homeostasis were completely absent in chronic decerebrate Ss. In separate experiments, intraoral intake and taste-reactivity responses elicited by intraoral infusions of NaCl were measured during sodium-replete and sodium-deficient conditions. In response to oral infusions of NaCl, intact Ss consumed significantly more and produced greater numbers of ingestive taste-reactivity responses when they were sodium deficient than when they were sodium replete. The same sodium-depletion treatments in chronic decerebrate Ss, however, altered neither the intraoral intake of NaCl nor the frequency of NaCl-elicited ingestive taste-reactivity responses. Results suggest that the behavioral compensatory responses that follow changes in the internal sodium state depend on forebrain mechanisms. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lithium chloride and avoidance of novel places.

In Exp I, 40 male hooded rats were exposed to a distinctive chamber (Chamber A, part of a 2-chamber apparatus) that was novel for half of the Ss but familiar for the other half. Each S was subsequently injected with lithium chloride or saline. In a test trial conducted 24 hrs later, all Ss were given a choice between Chamber A and Chamber B, which was novel for all Ss. The group made familiar with Chamber A and then given lithium showed a significant preference for that side or an avoidance of the novel side, a "spatial neophobia." Exp II, with 40 Ss, confirmed the spatial neophobia effect and demonstrated that it did not depend on the particular conditioning procedure used in the 1st experiment. The spatial neophobia effect was related to similar effects in the taste aversion literature and to the results of research on lithium-induced decreases in exploratory behavior. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Progesterone antagonism of androgen-dependent aggression-promoting pheromone in inbred mice (Mus musculus).

Conducted 2 experiments to investigate a possible antagonism between progesterone (P) and testosterone propionate (TP) with regard to the latter's role as a mediator of aggression-promoting pheromone. Ss were a total of 18 male BALB/cJ inbred mice trained as fighters and 64 castrated A/J male mice. Exp I showed that castrated Ss injected with TP were attacked by fighters faster, more often, and for a longer duration than castrates treated with TP and P. Exp II revealed that castrates coated with urine collected from castrated urine donors treated with TP were attacked more often and for longer periods than castrates coated with the urine of donors given TP and P. Thus, P appears to antagonize the effect of TP on aggression pheromone through a urinary pathway. The 2nd part of Exp II replicated and confirmed the results of Exp I. Results may be explained in terms of a peripheral biochemical antagonism with TP or, more likely, by the elicitation of inhibitory cues by P. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste reactivity as a dependent measure of the rapid formation of conditioned taste aversion: A tool for the neural analysis of taste-visceral associations.

Investigated the ability of animals to form taste aversions following neural manipulations. In Exp 1, 10 rats received intraoral infusions of sucrose every 5 min starting immediately after the injection of LiCl. 12 controls were injected with NaCl. Oromotor and somatic taste reactivity behaviors were videotaped and analyzed. Lithium-injected Ss decreased their ingestive taste reactivity over time; aversive behavior increased. Controls maintained high levels of ingestive responding and demonstrated virtually no aversive behavior following sodium injection. Ss were tested several days later for a conditioned taste aversion (CTA). Rats previously injected with lithium demonstrated significantly more aversive behavior than controls. Exp 3 revealed that when similarly treated rats were tested for a CTA while in a lithium-induced state, difference in the ingestive behavior was observed. In Exp 2, naive rats were injected with NaCl or LiCl but did not receive their 1st sucrose infusion for 20 min. Ss also received infusions at 25 and 30 min postinjection. There were no differences in the task reactivity behavior displayed. Rats dramatically changed their oromotor responses to sucrose during the period following LiCl administration, provided the infusions started immediately after injection, a change attributable to associative processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of prior exposure on conditioned taste aversion in the rat: Androgen- and estrogen-dependent events.

Studied the effects of preexposure and gonadal hormone manipulation on the extinction of a conditioned taste aversion in 198 male Sprague-Dawley rats. In Exp I, Ss were given 1 prior exposure to sucrose at some selected time (Days 4, 2, or 1) before a 2nd exposure (Day 0) to sucrose and a LiCl injection, or they were given only a single exposure (Day 0). Under single exposure, castrated Ss extinguished the aversion faster than either testosterone-treated castrated Ss or sham-operated Ss. In Exp II, estradiol, dihydrotestosterone, and testosterone were studied by using only a Day 1 preexposure condition. The testosterone-treated group maintained the aversion for the longest period, followed by dihydrotestosterone-treated, sham, castrated, and estradiol-treated groups. In Exp III, estradiol was administered alone or in combination with 2 doses of dihydrotestosterone. Findings indicate that the outcome of behavior was dependent on the ratio of estradiol to dihydrotestosterone, with variations in this ratio resulting in fast (estrogen effect) to slow (androgen effect) rates of extinction. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sham feeding in rats after ventromedial hypothalamic lesions and vagotomy.

Two studies examined sham feeding in female Sprague-Dawley rats with ventromedial hypothalamic (VMH) lesions with or without abdominal vagotomy. In Exp I, intact Ss consumed more than twice as much sweet milk during 1-hr tests of sham feeding as they did when feeding normally. Ss with VMH lesions showed exaggerated sham feeding, which was elevated almost four-fold over their already high normal feeding baseline. In Exp II, vagotomy substantially reduced sham feeding in Ss with VMH lesions. After vagotomy, VMH Ss sham fed half as much as nonvagotomized VMH Ss. Vagotomy did not, however, reduce sham feeding to control levels. Results are consistent with the hypothesis that VMH hyperphagia arise from exaggeration of orosensory responsiveness, which is, in part, a consequence of perturbed vagal function. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disruption of passive avoidance learning in the rat by electrical stimulation of the hippocampus.

Five experiments, with 184 male albino rats, examined the effect of electrical stimulation to discrete regions of the dorsal hippocampus on passive avoidance. Ss stepped from a brightly lit, white compartment to a dark compartment. Following footshock in the dark compartment, step-through latencies were recorded 1 min, 24 hrs, and 48 hrs after footshock. When given 20 step-through trials prior to footshock, dentate-stimulated Ss exhibited lack of passive avoidance with particularly short latencies at 1 min, and CA1-stimulated Ss showed reduced latencies compared with latencies of cortical and nonoperated controls. In Exp II, Ss given stimulation in the same regions performed the avoidance task without prior step-through experience. All groups showed less passive avoidance than the control group in Exp I, and there were no significant differences between groups. With a single step-through trial before the footshock trial, longer avoidance latencies were recorded, but again groups did not differ significantly. Dentate-implanted Ss, given 20 prior exposure trials but with stimulation at different stages of the task sequence, demonstrated a passive avoidance deficit at 1 min after footshock. Results are discussed in terms of the generation of expectancy that the black compartment was a safe place and the effects of brain stimulation on the expectancy, with particular reference to O. S. Vinogradova's (1975) theory of hippocampal function. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)