Effects of a synthetic facial pheromone on behavior of cats.

OBJECTIVE: TO evaluate the effects of a synthetic feline facial pheromone (FFP) on behavior and food intake of healthy versus clinically ill cats. DESIGN: Original study. ANIMALS: 20 cats were used in each of 2 studies. In each study, 7 cats were considered healthy, and 13 cats were determined to be clinically ill. PROCEDURE: In study 1, cats were assigned either to exposure to FFP (treated group; 4 healthy, 6 ill cats) or to exposure to the vehicle (70% ethanol solution; control group; 3 healthy, 7 ill cats). Cats were placed in a cage containing a small cotton towel that had been sprayed with FFP or vehicle 30 minutes previously. Cats were then videotaped for 125 minutes, and food intake was measured during this period. Videotapes were scored at 5-minute intervals for various behaviors. In study 2, cats were categorized in 1 of 2 groups; group 1 (2 healthy, 8 ill cats) had a cat carrier placed in their cages, and group 2 (5 healthy, 5 ill cats) did not. All cats were exposed to FFP, and 24-hour food intake was measured. RESULTS: Differences between behaviors of healthy versus clinically ill cats were not identified. In the first study, significant increases in grooming and interest in food were found in cats exposed to FFP compared with vehicle. For all cats, significant positive correlations were detected between grooming and facial rubbing, walking and facial rubbing, interest in food and facial rubbing, eating and facial rubbing, grooming and interest in food, and grooming and eating. In the second study, 24-hour food intake was significantly greater in cats exposed to FFP and the cat carrier, compared with cats exposed to FFP alone. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that exposure to FFP may be useful to increase food intake of hospitalized cats.

Effects of feline immunodeficiency virus on cognition and behavioral function in cats.

Experimental intravenous challenge of 8-week old cats with the Maryland isolate of feline immunodeficiency virus, Maryland isolate (FIV-MD) was investigated for its effects on cognitive and behavioral function at 12 months postinfection. Six cats infected with FIV-MD were compared with age-matched controls on several behavioral measures. These measures included an open field observation, locomotion tests, traversing planks of various widths for food reinforcement, and a spatial learning task. No group differences were observed on any measure of locomotion. Differences were present with exploratory and stationary activity in the open field observation, with infected cats exhibiting higher levels of exploratory activity and in less stationary activity compared with that of control cats. In the plank-walking experiment, infected cats were less able to successfully cross progressively narrower planks compared with control animals. A holeboard paradigm was constructed to test spatial learning and memory, in which cats were required to locate food reinforcement based on position in the holeboard array. As a group, FIV-infected cats committed more reference (exploring an unbaited cup) and working memory (returning to a previously visited baited cup) errors than control cats. The main difference demonstrated was a higher activity level and associated distractibility in FIV-infected cats that appears to be related to their overall deficient performance when learning new tasks. These results indicate that behavioral function is altered and cognition is quantitatively impaired in FIV-infected cats.

Performance by adult rats in sensory-mediated radial arm maze tasks is not impaired and may be transiently enhanced by chronic exposure to ethanol.

The effect of chronic exposure to ethanol on learning and memory was assessed in rats. Adult rats were fed a liquid diet containing ethanol (Et) ad libitum, pair-fed an isocaloric/isonutritious control diet (Ct), or fed lab chow and water (Ch) ad libitum. These diets were provided for as long as 28 weeks prior to testing and during the period of behavioral testing. Rats were required to learn a radial arm maze task that depended upon extramaze cues (visual and spatial) or intramaze cues (various odors). Each rat was tested twice daily for 26 days. The number of reference and working memory errors and the time required to successfully navigate the maze (latency) were recorded. Et-fed rats consistently performed the same or better than the Ct-fed or Ch-fed rats. The enhanced behavior was task-specific and transient. The enhancement was observed in rats after 14 or 20 weeks of ethanol exposure, but not in rats exposed to ethanol for 28 weeks. Et-fed rats performed significantly better on the reference memory task in the odor condition of the maze task, whereas their performance in the spatial task was similar to that for the two control groups. Thus, after an extended period of exposure (e.g., 28 weeks), ethanol had no effect on learning and memory. On the other hand, under certain conditions (14 or 20 weeks), ethanol transiently enhanced memory.

Onset of tolerance to discriminative stimulus effects of morphine.

Experiments assessed the onset of tolerance to discriminative stimulus effects of morphine in rats treated repeatedly with twice daily doses of 10 mg/kg morphine. Saline and 3.2 mg/kg morphine were established as discriminative stimuli for food-reinforced fixed-ratio performances in several groups of rats, and initial ED50 values were determined for stimulus and rate-altering effects of morphine. To assess onset of tolerance, training was halted and 10 mg/kg doses of morphine were administered repeatedly at 12-h intervals. In separate experiments, ED50 values were redetermined after various treatment periods. One treatment with 10 mg/kg morphine did not alter the ED50 for stimulus effects of morphine, whereas treatment for one or three days increased the ED50 by approximately 2-fold. Comparisons with published data showed even greater tolerance when treatment lasted one or two weeks. Tolerance to stimulus effects of morphine generally was accompanied by tolerance to its rate-decreasing effects. Repeated treatment with morphine also produced cross-tolerance to morphine-like stimulus effects of methadone and buprenorphine. As with morphine itself, greater tolerance developed with longer treatment. These results suggest that tolerance to discriminative stimulus effects of morphine develops gradually, with magnitude of tolerance increasing as a function of treatment duration.

Tolerance to morphine stimulus control: role of morphine maintenance dose.

Experiments assessed the development of tolerance to morphine stimulus control during treatment with selected maintenance doses of morphine. Separate groups of rats were trained to discriminate saline and either 3.2 mg/kg or 5.6 mg/kg morphine under fixed-ratio schedules of food delivery. Dose-response functions for generalization of morphine stimulus control were determined before, during, and after repeated treatment with selected doses of morphine. Similar experiments were performed with repeated pentobarbital treatment in order to assess the pharmacological selectivity of tolerance. Repeated treatment with saline, 3.2 mg/kg morphine, or twice daily injections of 17.8 mg/kg pentobarbital produced no tolerance to morphine stimulus control. In contrast, treatment with daily injections of 10 mg/kg or twice daily injections of 10 or 17.8 mg/kg morphine produced a dose-dependent increase in the dose of morphine required for stimulus control. The magnitude of tolerance to morphine stimulus control varied directly with the maintenance dose of morphine and was slightly greater for a lower than a higher morphine training dose. Termination of repeated treatment was followed by a return to initial sensitivity, without additional training. Tolerance to morphine stimulus control was not necessarily accompanied by tolerance to its rate-suppressing effects.

Aversive conditioning properties of caffeine in rats.

Four experiments tested the conditioning effects of caffeine. Flavor and place cues were paired with IP caffeine injections and followed by tests for cue preference. In Experiment 1A, saccharin was paired with 1.25, 5 or 20 mg/kg of caffeine. In Experiment 1B, caffeine was delivered 30 min before, 5 min before, or 30 min after saccharin. Dose- and time-dependent conditioned taste aversions were produced. In Experiment 2, a place and taste cue were paired simultaneously with 5 or 20 mg/kg of caffeine. Conditioned place and taste aversions developed at 20, but not at 5 mg/kg. In Experiment 3, a place cue alone was paired with 0, 5, or 20 mg/kg of caffeine; dose-dependent conditioned place aversions developed. In Experiment 4, place and taste cues were paired with control treatments: pH-buffered caffeine, purine or vehicle. Caffeine produced taste aversions whereas the purine and vehicle did not. These aversive conditioning effects of caffeine across a variety of situations, doses and temporal arrangements stand in contrast to results obtained with other psychoactive drugs, such as amphetamine and alcohol.