Rat behavior and dopamine release are modulated by conspecific distress

Rats exhibit ‘empathy’ making them a model to understand the neural underpinnings of such behavior. We show data consistent with these findings, but also that behavior and dopamine (DA) release reflects subjective rather than objective evaluation of appetitive and aversive events that occur to another. We recorded DA release in two paradigms: one that involved cues predictive of unavoidable shock to the conspecific and another that allowed the rat to refrain from reward when there were harmful consequences to the conspecific. Behavior and DA reflected pro-social interactions in that DA suppression was reduced during cues that predicted shock in the presence of the conspecific and that DA release observed on self-avoidance trials was present when the conspecific was spared. However, DA also increased when the conspecific was shocked instead of the recording rat and DA release during conspecific avoidance trials was lower than when the rat avoided shock for itself.

Behaviour, brain and body growth of guinea-pigs after prenatal growth restriction

1. Guinea-pigs were growth-retarded in early life by feeding their mothers a restricted quantity of food during the second half of pregnancy. After birth, all animals were fed ad lib. Body-weights were recorded weekly and behavioural tests were made on adult males. The animals were then killed and their brains dissected into forebrain, cerebellum and brain stem. These regions were weighed and DNA-phorphorus content measured.2. At 14 weeks each male was paired with another male for 10 min on four consecutive days and their social behaviour scored. Tests 1 and 2 were on like-treatment pairs and tests 3 and 4 on unlike-treatment pairs. At 25 weeks the same animals were subjected to six graded series of brief, unavoidable shocks and their responses recorded. After 3 d, thresholds of aversion to electric shock were measured by recording the period of time spent on the ‘safe’ side of a rectangular box at five shock levels.3. Undernourished guinea-pigs were significantly lighter than controls at birth but not at adulthood. Regional brain weights and DNA-P content of previously-undernourished guinea-pigs were significantly lower than those of controls, with the greatest deficit in brain stem.4. Pairs of previously-undernourished guinea-pigs began to interact more quickly and threatened and nosed each other more often than pairs of controls. In mixed pairs previously-undernourished animals chased controls more than their control partners chased them. There were no differences between groups in responsiveness to unavoidable shock or in aversion thresholds.

Effects of Chlorpromazine on Fear-Motivated Behavior, Urinary Cortisol, Urinary Volume and Heart Rate in the Dog

Several doses of chlorpromazine (6.25, 12.5, 25.0 mg) were administered to dogs while they were subjected to a Sidman nondiscriminated avoidance schedule which contained 7 conditioned stimuli-unavoidable shock (CS-US) pairings. The drug consistently reduced baseline response rate and enhanced shock rate. Facilitation of heart, response, and activity rates normally noted during the aversive CS were unaffected by administration of the drug. In addition, the over-all heart rate, urinary volume, and urinary Cortisol measures showed no consistent pattern of results in response to drug administration. These results suggest that under this schedule of reinforcement only baseline response rate was sensitive to the anxiolytic effects of chlorpromazine.

Effects of Chlordiazepoxide upon Fear-Motivated Behavior in Dogs

Several doses of chlordiazepoxide (45, 100, 200 mg) were administered to dogs while they were subjected to a Sidman nondiscriminated avoidance schedule which contained seven conditioned stimuli-unavoidable shock (CS-US) pairings. The drug reliably reduced baseline response rate and significantly inhibited the amount of urinary cortisol excreted during the experimental sessions. Facilitation of heart, response, and activity rates normally noted during the aversive CS were unaffected by administration of the drug. In addition, over-all heart rate showed no consistent pattern of results in response to drug administration. These results suggest that under this schedule of reinforcement only the baseline response rate and urinary cortisol measures were sensitive to the antianxiety effects of chlordiazepoxide.

Anticholinergics: Their Effects on Fear-Motivated Behavior, Urinary 11-Hydroxycorticosteroids, Urinary Volume, and Heart Rate in the Dog

Two anticholinergics (scopolamine hydrobromide and scopolamine methylbromide—.5, .7 mg) were administered to dogs while they were subjected to a Sidman nondiscriminated avoidance schedule which contained seven conditioned stimuli-unavoidable shock (CS-US) pairings. Both anticholinergics significantly elevated urinary 11-hydroxycorticosteroids and heart rate, while only the central acting agent, scopolamine hydrobromide, affected behavior. These results suggest that the behavioral effects of scopolamine hydrobromide are not mediated through its effects on the adrenal-pituitary system. Response rates under scopolamine hydrobromide were substantially reduced leading to increased shock rates, especially during the CS segments of this schedule. These behavioral results were interpreted to suggest that cognitive (possibly memory) functions were altered in response to scopolamine administration.