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Biomedical subjects

E Fonberg

Publications and source records attributed to E Fonberg.

At least 19 recordsLinked to original sources
PubMed1993

The alimentary and social instrumental performance in dogs is suppressed by various doses of amphetamine.

Amphetamine was administrated intramuscularly 20-25 min before each experimental session in doses of: 0.2 mg/kg, 0.5 mg/kg and 1.0 mg/kg. Each dose was applied twice and preceded by a regular experimental sessions without any treatment. An instrumental performance consisted of alimentary-social differentiation of two tones reinforced either by food or by sensory-social reward (petting by the experimenter). Amphetamine produced dose dependent decrease of the instrumental performance of both alimentary and social responses. This decrease was however not equal regarding both reactions. The dose of 1 mg/kg produced deep, statistically significant deterioration of alimentary as well as social responses. After the administration of the dose of 0.5 mg/kg the decrease of alimentary responses was equal to that produced by 1 mg/kg, whereas social responses were less deteriorated. After the dose of 0.2 mg/kg the reduction of alimentary responses was smaller than produced by 0.5 mg/kg but still more pronounced than in the case of socially reinforced reactions. The results confirm our previous data that amphetamine suppresses positively motivated instrumental performance in dogs. The results also show that amphetamine-evoked suppression is dose dependent and that it is different for alimentary and social responses. This might indicate that the positive reward system is not homogenous but consists of some subsystems related to different kinds of reward. It is concluded that the suppressing effect of amphetamine is due to the inhibitory effect on motivation, but not on purely instrumental mechanisms nor on hedonic processes.

Amphetamine↗
PubMed1992

Chlorpromazine exerts stronger suppressive action on the instrumental responses motivated by social than by alimentary reward.

Experiments were performed on six dogs over-trained before treatment, in differentiation of two instrumental responses, i.e. reinforced either by food or by sensory-social reward (petting by the experimenter). Chlorpromazine was injected intramuscularly (1.5 mg/kg) in two separate series. In the first series the drug was given four times during two weeks (twice a week). In the second series, it was injected every day for four consecutive days. Chlorpromazine produced a decrease of performance and an increase of response latencies and errors but this effect was much more evident with social than with alimentary reward. The effect of the drug was similar in both variants of the experiment, although it was more pronounced in the second than in the first series. Food intake was not changed. The motor and autonomic disturbances produced by the drug were not correlated with the decrease in instrumental performance. It is suggested that chlorpromazine acts rather on motivational or rewarding processes than on hunger drive or instrumental performance as such.

Animals↗
PubMed1990

Heart rate changes during consumption of preferred and non-preferred food under amphetamine treatment.

Heart rate was recorded in five dogs while they ate three kinds of foods varying in preference. Heart rate increased during the initial phase of eating, to the greatest extent with the most preferred food. dl-Amphetamine sulfate (0.2 mg/kg) injected intramuscularly produced a general decrease of heart rate. Nevertheless, the heart rate increase during first period of eating was as great as before treatment. Furthermore, the difference in heart rate increase between the most and least palatable foods was still present, and in some dogs even enhanced. It was concluded that amphetamine at this dose in dogs does not attenuate the hedonic properties of food, but may even intensify them. Therefore, the food intake-reducing effect of amphetamine cannot be due to its suppression of hedonic value of food but is the result of its action on other mechanisms such as hunger drive or control of movement.

Amphetamine↗
PubMed1989

Amygdala, depression and drug treatment.

The problem of the mechanisms of depression and action of the depressive drugs needs theoretical analysis and multichannel investigations. Animal models of depression are important for such investigations. Various neurochemical behavioral and psychological models were analysed in the present paper. Amygdalar model of depression seems to be one of the most important models. The effects of the treatment by amphetamine, imipramine and chlorpromazine on the amygdalar depressive syndrome in dogs were described. The individual differences were stressed, both in respect to forms of particular depression and to the sensitivity to drug treatment.

Amygdala↗
PubMed1988

Dominance and aggression.

Dominance is a complex phenomenon mediated by different mechanisms. Various motivations and their mutual correlations determine the tendency to dominate. A subject that is dominant in every situation (i.e., absolutely dominant) is rather an exceptional case. Dominance may be limited to particular situations and exhibited only with some definite partners. One subject may be dominant over one partner and submissive with another. Aggressive behavior is not indispensable to obtain and keep dominance status. It seems that dominance sustained without aggression is more stable than dominance formed on the basis of aggressive display, since experiments on predatory dominance in pairs and groups of cats support such an assumption. Various brain structures were found which are involved in aggressive behavior, but in respect to dominance our experiments point to the role of the dorsal amygdala in predatory dominance.

Aggression↗
PubMed1987

The effect of imipramine on predatory behavior and locomotor activity in cats.

The behavior toward mouse was studied under and after chronic imipramine treatment in two groups of cats - non-killers and killers. Imiprarnine facilitated predatory behavior in the non-killers but not in the killers, which is in contrast to results obtained on rats. Imipramine produced a marked decrease of locomotor activity of non-killers tested in open field. The inhibition of locomotion did not interfere with the occurrence of killing behavior. It was concluded that imipramine selectively facilitates the neurophysiological mechanism of predatory behavior, which in cats might be connected with the reward system.

Animals↗
PubMed1987

Comparison of the effects of lateral and ventro-posterior hypothalamic damage on the predatory behavior of cats.

Two groups of seven cats estimated preoperatively as good mice-killers were subjected to the damage of either the lateral hypothalamus (LH) or the ventro-posterior hypothalamus (VPH). The LH damage produced global impairment of the predatory behavior, such as interest in, catching, killing, or consuming the mouse, whereas VPH damage left intact most components of the predatory act, except for mouse consumption. Changes in food preference, i.e. the choice between mice and meat, were found in both groups of cats. Instead of the preoperative preference of mouse over meat, postoperative preference of meat was found in both groups. Postoperative restoration of the predatory behavior, observed in both groups, proceeded faster in the VPH cats than in the LH cats, for which the impairment lasted for several months.

Animals↗
PubMed1986

Changes in socio-emotional behavior under imipramine treatment in normal and amygdalo-hypothalamic dogs.

The effects of imipramine on learned social responses were examined in ten dogs with dorsomedial amygdalar lesions and/or lateral hypothalamic lesions. Six of the ten dogs were also tested preoperatively. The social responses were instrumentally conditioned using social interaction with the experimenter as reinforcement (petting and verbal reassurance). In the non-lesioned dogs imipramine treatment produced a dose-dependent deterioration of performance during drug administration followed by a long-term amelioration of performance. In the lesioned dogs imipramine produced various changes in performance depending on the pretreatment level of responding. When the pretreatment level of performance was high drug administration resulted in a long-term deterioration, and when performance was poor imipramine produced a continuous and long-term increase. It is suggested that imipramine facilitates the recovery of performance, but suppresses well-performed responses.

Amygdala↗
PubMed1985

Predatory dominance and aggressive display under imipramine treatment in cats.

The effect of imipramine treatment on the aggressive display and predatory dominance was tested in 16 male cats yoked in 8 pairs. Imipramine applied chronically during 3 weeks in submissive cats produced a tendency to compete with the dominant cat in a predatory situation and an accompanying enhancement of aggressive display. Some of the treated cats gained the predatory dominance over previously dominant partners. The level of aggressiveness was not, however, directly related with the process of gaining dominance. Therefore it was concluded that imipramine enhances some mechanisms involved in dominance, not limited to aggression.

Aggression↗
PubMed1984

Food-motivated behavior in rats with cortico-basomedial amygdala damage.

Twelve rats with amygdala damage (CBM) and 20 sham-operated controls were tested in several food-related situations. The CBM rats showed a longer latency to eat than controls in a novel environment due to more pronounced exploration. In the competition for food, CBM rats lost 85% of encounters with controls. Immediately after the contest, when allowed to eat singly, CBM rats displayed a higher persistence of alimentary responses to an emptied cup than did controls, presumably because they experienced more losses in the food competition. Both groups were equally able to overcome obstacles on the way to food, which suggests similar alimentary motivation. The only direct indication of a lowered responsiveness to hunger in CBM rats was 24-hr-fasting-induced hypophagia. The results of this study indicate the involvement of the cortico-basomedial amygdaloid region in the control of relations between alimentary and other motivations. The contribution of eventual changes of food motivation in the postoperative alteration of this balance is discussed.

Amygdala↗
PubMed1983

Impairment of social behavior in amygdalar cats.

Social dominance in predatory animals was tested before and after amygdala lesions. Cats after damage of dorsal part of amygdala did not show predatory behavior in group and lost their social rank in hierarchy, but in the same animals predatory attack remained unchanged in nonsocial situations. In the cat with medial amygdala lesions total abolishment of mouse-killing behavior was observed in both social and nonsocial situations. It has been concluded that amygdala plays an essential role in emotional-motivational mechanisms of predatory competitions as one of the forms of social behavior.

Amygdala↗
PubMed1982

Heart rate mechanisms in instrumental conditioning reinforced by petting in dogs.

The aim of this experiment was to determine heart rate (HR) responses during conditioned stimuli (CS) and the petting reward (US) delivered by the experimenter to the dogs after performance of the instrumental conditioned response (CR). It was found that in five dogs for which petting served as a positive reinforcement the delivery of petting was accompanied by cardiac deceleration followed by sudden acceleration at the moment of petting withdrawal. Presentation of CS evoked heart rate deceleration until performance of the first CR. At the start of performance of CRs, heart rate accelerated. It was suggested that heart-rate deceleration is an important component of cardiac response to petting reward and, that probably, it is associated with the hedonic aspect of the reinforcement.

Animals↗
PubMed1982

Autonomic responses accompanying conditioned and unconditioned alimentary reactions in amygdalo-hypothalamically lesioned dogs.

Lesions in the amygdalo-hypothalamic system decreased conditioned and unconditioned alimentary responses in five dogs. During three postoperative months no improvement was observed. The introduction of the new food reward (chosen for each dog as the most preferred) produced a sudden or progressive increase of conditioned and unconditioned alimentary performance. In the cardiac responses accompanying postoperative conditioned and unconditioned alimentary reactions, the lack or diminution of the decelerative response during food .consumption and a less pronounced postoperative acceleration of heart rate during conditioned stimuli were observed. Conditioned and unconditioned salivary responses decreased postoperatively and the pattern of the salivary responses varied individually. The results support the hypothesis that damage of amygdalo-hypothalamic system produces a decrease of the hedonic values of the usually used food rewards. Decrease or lack of the decelerative cardiac response during eating may reflect this ahedonic state.

Amygdala↗
PubMed1982

The effect of medial amygdala lesions on instrumental sexual responses in male rats.

In male rats bar press responses reinforced by the contact with estrous females were established during the preoperative training. Bilateral electrolytic lesions of the medial amygdala nuclei caused an impairment of copulatory behavior manifested by the appearance, during male-female contacts, of exploratory behavior or body investigation instead of copulatory behavior. In all subjects such noncopulatory contacts occurred alternately with those when the copulations took place. The latencies of instrumental responses immediately following the contacts during which intromissions took place remained unchanged. It is suggested that the medial amygdala exerts excitatory and regulatory influences on sexual arousal mechanisms in male rats.

Amygdala↗
PubMed1981

Reflex EMG activity in rats with lesions of medial amygdala.

Lesions effects of the medial amygdala on spinal reflexes were studied in 6 rats using chronic EMG recording and were not found influential. These results suggest that behavioral changes previously observed m such rats were not produced by sensory-motor disturbances.

Achilles Tendon↗