Learned aversions to proteins in rats on a dietary self-selection regimen.

101 Long-Evans and 38 Wistar rats in 4 experiments were allowed continuous access to protein and carbohydrate macronutrient sources during a sequence of cyclophosphamide (20 or 40 mg/kg, ip) injections. Significant aversions developed to the protein but not the carbohydrate source in the present experiments, in which the composition of both protein and carbohydrate diets was varied. Results suggest that Ss on a dietary self-selection regimen were more likely to develop conditioned aversions to the protein source than the carbohydrate source (Exps I, II, and III). In Exp IV, the generality of these findings was examined by determining whether aversions would selectively arise to proteins but not carbohydrates when these nutrients were conditioned in a single trial with a meal-feeding paradigm. Results show that proteins were again more salient targets for aversions than carbohydrates. Overall, findings suggest that the tendency to associate proteins with drug-induced illness more readily than carbohydrates is not limited to a self-selection regimen. The possible role of taste factors and/or postingestive effects as the basis for the differential conditioning of proteins and carbohydrates is discussed. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of yohimbine and naloxone on copulatory behaviors of male rats.

Prior research has demonstrated that both yohimbine, an alpha?-adrenergic antagonist, and naloxone, an opiate antagonist, facilitate components of copulatory behaviors in nonstressed male rats. In the present experiments, it is demonstrated that these drugs differentially affect copulatory behaviors when the behavioral testing situation contained an aversive element. Male rats received an injection of lithium chloride (0.3 M, 20 ml/kg, ip) immediately after each encounter with an estrous female. Consequently, male copulatory behaviors gradually declined during successive test sessions. These male rats also received ip injections of either yohimbine (2 mg/kg/ml), naloxone (4 mg/kg/ml), or isotonic saline 20 min prior to each copulation test. Yohimbine-treated rats were more likely to copulate than control rats during both acquisition and extinction of lithium chloride-induced associative inhibition of copulatory behavior. Conversely, naloxone-treated rats were less likely to copulate than control rats during both acquisition and extinction. Data are consistent with the hypothesis that yohimbine increases sexual motivation in the male rat and limit the generality of the excitatory effects of naloxone on copulatory behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned taste aversions over long delays in rats: The role of learned safety.

Tested the proposal that learned safety accounts for the delay gradient in learned taste aversions in 4 experiments. In Exp I and II, 132 female Sprague-Dawley rats drank a small quantity of a nontoxic solution toward which they had a mild aversion. It was found, in support of the learned safety concept, that the intake in a 2nd test was a function of the delay time between tests. Exp III with 72 Ss demonstrated that no additional curve of learned safety would occur when Ss had previously received extensive experience with the solution. Exp IV with 81 Ss found, however, that learned safety was not a sufficient explanation for the delay gradient in learned taste aversions by showing that the gradient still persisted even when the experimental procedure minimized the effects of learned safety. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Computer programs to analyze brain electrical activity during copulatory pelvic thrusting in male rats

Two microcomputer programs have been developed to simultaneously record and analyze the brain electrical activity: multiple unit activity (MUA) and electroencephalogram (EEG), and the accelerometric signals generated in relation to the pelvic thrusting that performs the male rat during the copulatory responses of mount, intromission, and ejaculation. CAPTUMUL is a program allowing the on line capture of the different signals and the further off line delimitation of the brain signals occurring in exact temporal relation with the accelerometric record of motor responses. The ANAMUA program allows the off line analysis of the neuronal firing rate in MUA records at different discrimination levels according to the amplitude of the neuronal spikes, and compare these data in various behavioral situations. The use of these programs provides a way of correlating in time the changes of brain electrical activity occurring in animals in free-movement with the brief motor events of copulation as well as with other behaviors (i.e., genital grooming, sniffing, running, walking). Advantages of this software include the recording of sequential events, a better and rapid handling of data and a reliable method to analyze the MUA with different discrimination levels according to the amplitude of the neuronal spikes.     

Cooling the area postrema induces conditioned taste aversions in male rats and blocks acquisition of LiCl-induced aversions

The experiments presented in this article were designed to examine whether area postrema (AP) lesions attenuate LiCl-induced conditioned taste aversions (CTAs) by disruption of information about the illness-producing properties of LiCl or by a lesion-induced malaise. Reversible lesioning of the AP caused by cooling induced a CTA in male rats. The cooling-induced CTA could be blocked if males were exposed to cooling for several days before acquisition day. Acquisition of a LiCl-induced CTA was blocked in males if they were exposed to cooling before acquisition day and during LiCl administration on acquisition day was attenuated but not blocked in males if they were exposed to cooling only before acquisition day, and was unchanged in males if they were exposed to cooling only during LiCl administration. Taken together these results indicate that the AP is important for acquisition of LiCl-induced CTAs but that inactivation of this area is so aversive it will induce CTAs that can obscure the attenuation of LiCl-induced aversions.     

Responses to copulatory stimulation in neonatally androgenized female rats.

Five experiments evaluated the extent to which copulatory stimulation could ameliorate the anestrus and sterility exhibited by neonatally androgenized female Long-Evans rats (N?=?102). The age at which Ss began to exhibit persistent vaginal estrus and the degree of sexual receptivity exhibited under several testing paradigms were found to be inversely related to the dose of testosterone propionate (TP) injected neonatally. With increasing numbers of mounts received, both the number of androgenized Ss exhibiting sexual receptivity and the quality of the estrous behavior exhibited tended to increase. Ss injected with high doses of TP (500 μg) usually showed little or no receptive behavior even in the most extensive behavioral tests. However, under some testing conditions Ss receiving 50 μg of TP neonatally, while showing little or no receptivity during initial mounts, showed increased receptivity as behavioral tests were extended. Following matings that included 1–5 ejaculations, only control Ss were observed to become pregnant. However, when androgenized females cohabited with males for an extended period, Ss that had neonatally received .5 μg of TP, but not higher doses, did become pregnant. It is concluded that (1) the capacity of systems mediating reproductive physiology and behavior is facilitated by stimuli associated with males; and (2) mating is a characteristic of the female rat, which can be manipulated by injection of hormones during the neonatal period. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrical stimulation of dorsal and ventral striatum differentially alters the copulatory behavior of male rats.

Sexual behavior is a natural reward that activates striatal dopaminergic (DA) circuits, and dopamine exerts a facilitative influence on copulation. Electrical stimulation of the striatum has been shown to be rewarding, but its effect on male sexual behavior display has not been established. The objective of the present work was to assess the effects of low- and high-frequency electrical stimulation of the dorsal and ventral striatum on male rat sexual behavior expression. To this aim, copulatory activity of sexually experienced male rats was recorded during electrical stimulation of the nucleus accumbens (NAcc) or caudate-putamen (CP), at each stimulation frequency, before and after sexual exhaustion. Results showed that electrical stimulation of the NAcc at both frequencies increased the number of ejaculations that male rats were able to show in a 30-min period. By contrast, stimulation delivered to the CP inhibited sexual behavior by slowing its display. Each effect was more pronounced at low than at high stimulation frequencies. In the same rats, once sexually exhausted, electrical stimulation of these brain areas did not reverse the sexual behavior inhibition that characterizes the sexual exhaustion state. It is concluded that dorsal and ventral striatal DA brain regions exert opposite influences on copulatory behavior expression of sexually experienced male rats. Also, that the facilitative effect of NAcc electrical stimulation on sexual activity, with the stimulation parameters used, cannot surmount the sexual behavior inhibition resulting from copulation to satiation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Specificity of acquired aversions to taste qualities in hamsters and rats.

372 golden hamsters and 120 Sprague-Dawley rats tasted 1 of 27 solutions before receiving an ip injection of apomorphine, then were tested for aversions to 4 solutions prototypic of human taste qualities: sucrose, NaCl, HCl, and quinine HCl. With most of the solutions described as sweet employed as CSs, Ss acquired an aversion to sucrose. With CSs described as either salty or sour by humans, Ss acquired an NaCl aversion in the former case or an HCl aversion in the latter case; an aversion to quinine HCl was acquired with 2 of the 3 CSs described as sour. With most of the CSs described as bitter or as having a bitter component, Ss acquired a quinine HCl aversion. Patterns of S activity evoked across 4 classes of peripheral gustatory neurons when the CSs were applied to the tongue were similar to the patterns of aversions across the 4 test stimuli for the CSs. This suggests that 4 neural channels mediate the sensations evoked by the 4 test solutions in rats and hamsters, perhaps even in human beings. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Odor and taste aversions conditioned in anesthetized rats.

Conditioned flavor aversions (CFA) are acquired by anesthetized rats but effects of various anesthetics on acquisition of aversions for separate odor and taste components are unknown. In Experiment 1, rats drank tomato juice and then were tranquilized with "Innovar-Vet" or "Rompun" before receiving injections of lithium chloride. Neither drug interfered with acquisition of aversions. Innovar-Vet alone produced no aversions; Rompun alone produced mild aversions but did not enhance aversions when combined with lithium. In Experiments 2 and 3, rats received a compound odor/taste cue as they drank and then were anesthetized with pentobarbital before lithium injections. Anesthesia alone produced negligible aversions but facilitated taste-lithium aversions. During odor tests, odor aversions were weaker than taste aversions. These data extend previous work and suggest that CFA does not result from ordinary classical conditioning. A tripartite notation that unites CFA and classical conditioning is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alterations of male sexual behavior by learned aversions to hamster vaginal secretion.

32 male hamsters poisoned after their 1st adult exposure to the vaginal secretion of female hamsters became hesitant to approach and ingest the secretion. The same aversion-training procedure also altered the responses of males to estrous females, changing the latency, frequency, and duration of a variety of behaviors that are commonly taken as indexes of sexual attraction or arousal and of copulatory performance. Results suggest that the aversions to vaginal secretion alter the perceived meaning of the secretion for male hamsters, and analysis of the correlations between various measures of sexual arousal and performance support the hypothesis that separate mechanisms underlie the effects of the secretion on appetitive and consummatory sexual behavior. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure of recovered lateral hypothalamic rats to learn specific food aversions.

Assigned 16 female Sprague-Dawley albino rats to either a group receiving lesions of the lateral hypothalamus, a group receiving lesions of the ventromedial nuclei of the hypothalamus, or a control group. After lesioned Ss recovered the ability to feed voluntarily, Ss were exposed to a procedure in which intake of a preferred diet was followed by LiCl poisoning. Whereas unoperated controls decreased subsequent intake of this diet and showed an aversion to it on a later preference test, most lesioned Ss showed little or no sign of having learned to avoid the poison-paired food. There was evidence, however, that the ability of brain-damaged Ss to learn this avoidance recovers over time. In Exp. II, intake of another preferred diet was accompanied by shock to the tongue. Again, lesioned Ss, unlike unoperated controls, appeared unable to associate ingestion of the diet with its aversive consequences. (35 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Life-span changes in the copulatory behavior of male rats (Rattus norvegicus).

Studied the copulatory behavior of 36 5-, 10-, 15-, and 20-mo old sexually naive male Long-Evans rats during 2-hr tests with receptive females. There was no apparent change in sexual arousal as measured by latency to initiate copulation across age, with Ss from all groups exhibiting comparable latencies to 1st mount and 1st mount with intromission. The numbers of ejaculations achieved were also similar across ages. Significant age differences were found for frequency of mounts, with 20-mo olds having the highest mean frequency. The persistent mounting by older Ss appeared to account for significant group differences in interintromission interval and ejaculation latency. It is suggested that motor deficits may impair the ability of older Ss to achieve intromission, increasing the number of mount bouts as well as the number of mounts for each bout, thus extending the length of each copulatory series. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversal of conditioned aversions in normal and micrencephalic rats.

When administered to pregnant rats, the drug methylazoxymethanol acetate (MAMA) causes a dose-dependent reduction in the mass of the cerebral cortex of the offspring. In the present experiment, it was found that MAMA-produced micrencephalic female hooded Long-Evans rats developed conditioned flavor aversions as easily as 10 normal controls. Both normal and micrencephalic Ss reversed a relative preference between 2 flavors easily and repeatedly. Results are discussed in relation to various contemporary theories of conditioned aversions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vagotomy facilitates extinction of conditioned taste aversions in rats.

Results from 3 experiments indicate that severing the subdiaphragmatic vagus in male Sprague-Dawley rats increased the rate of extinction of learned taste aversions. In Exp I, when the illness-inducing agent was the blood-borne toxin apomorphine, vagotomized Ss tended to consume more saccharin than controls during repeated extinction tests. In Exp II, vagotomy disrupted retention and increased extinction of a preoperatively acquired saccharin aversion. Disruptions were found when the taste aversion was induced by copper sulfate, a local gastric irritant, or apomorphine. Exp III demonstrated that vagotomy did not affect retention or extinction of a shock-induced conditioned emotional response to noise. It is concluded that integrity of the vagus is not necessary for acquisition of a learned taste aversion when a blood-borne toxin is used as the illness-inducing agent. However, the vagus apparently mediates an integral portion of the CR following taste–illness acquisition. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oxytocin and vasopressin secretion in response to stimuli producing learned taste aversions in rats.

In 5 experiments, administration of lithium chloride, copper sulfate, and apomorphine to male Sprague-Dawley rats each stimulated the secretion of oxytocin (OT) and, to a much lesser degree, arginine vasopressin. These agents are assumed to cause visceral illness in rats because of their effectiveness in promoting the acquisition of learned taste aversions (LTAs). CuSO?, but not LiCl, had a greater effect on plasma OT levels when administered intraperitoneally rather than intravenously. Results suggest that LiCl stimulates OT secretion by central chemoreceptor activation, whereas CuSO? acts predominantly by local peritoneal irritation. A causal role for circulating OT in the acquisition of LTAs was not found. Peripheral levels of OT may represent a quantifiable marker of visceral illness in rats and therefore might be useful in the interpretation of behavioral studies in which CTAs are produced, provided that other stimuli of neurohypophyseal secretion are absent. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of copulatory behavior in male Japanese quail

The copulatory behavior of sexually experienced male Japanese quail was tested using taxidermic models with varying proportions of natural and artificial features. Completely artificial models exerted little control over copulatory behavior, and whole natural body models reliably elicited copulatory behavior. In single model presentation tests, a model containing a natural head and neck with an artificial body was as effective in eliciting copulatory behavior as a whole body model, but a model containing a natural body with an artificial head and neck was largely ineffective. In choice tests, however, males clearly preferred a whole model over a natural head and neck model, and a natural body model over a completely artificial model. These data indicate male Japanese quail do attend to features of body plumage. Furthermore, test procedures can influence conclusions about effective controlling stimuli.     

Learned tolerance to ethanol-induced c-Fos expression in rats

This study examined the efficacy of eye movement desensitization and reprocessing (EMDR) and exposure in the treatment of a specific phobia. Twenty-six spider phobic children were treated during 2 treatment phases. During the first phase, which lasted 2.5 hr, children were randomly assigned to either (a) an EMDR group (n = 9), (b) an exposure in vivo group (n = 9), or (c) a computerized exposure (control) group (n = 8). During the 2nd phase, all groups received a 1.5-hr session of exposure in vivo. Therapy outcome measures (i.e., self-reported fear and behavioral avoidance) were obtained before treatment, after Treatment Phase 1, and after Treatment Phase 2. Results showed that the 2.5-hr exposure in vivo session produced significant improvement on all outcome measures. In contrast, EMDR yielded a significant improvement on only self-reported spider fear. Computerized exposure produced nonsignificant improvement. Furthermore, no evidence was found to suggest that EMDR potentiates the efficacy of a subsequent exposure in vivo treatment. Exposure in vivo remains the treatment of choice for childhood spider phobia.     

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)     

THC-induced place and taste aversions in Lewis and Sprague-Dawley rats.

The hedonic properties of delta-9-tetrahydrocannabinol (THC) were assessed in place and taste conditioning paradigms in both Lewis and Sprague-Dawley rat strains. THC produced place avoidance, taste avoidance, and aversive taste reactivity responses in both strains. The Lewis strain displayed more aversive taste reactions and a stronger taste avoidance when conditioned with lower doses of THC than did the Sprague-Dawley strain of rats. THC is an anomalous drug of abuse that appears to be aversive to rats when assessed by these measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ventromedial hypothalamic lesions on conditioned sucrose aversions in rats.

Maintained 11 female Wistar rats with lesions of the ventromedial hypothalamus (VMH) at 95% body weight (BW) and gave them an intraperitoneal injection of a 2% BW dose of .15 M lithium chloride following the consumption of sucrose pellets. Control groups (N = 18) maintained at 95 and 80% BW received the same treatment. The VMH and 80% groups showed less aversion to sucrose than the 95% group. Results suggest that appetitive passive-avoidance deficits in VMH-lesioned rats may be produced by increased hunger motivation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)