Emotional-aversive nature of the behavioral response induced by carbachol in cats.
Intrahypothalamic-preoptic application of carbachol induces a characteristic, emotional-aversive response in cats similar to their natural defensive behavior. This study was undertaken to provide quantitative evidence that the magnitude of the carbachol-induced, emotional-aversive response follows the same rules as natural responses to threat. An aversive emotional response can be described in terms of a spatiotemporal relationship between the animal and the relevant threat stimulus (potential danger). The physical distance to the threat stimulus and its movements should be predictive of the magnitude of the emotional response. The goal of the study was to test the relationship for the carbachol-induced response. The presentation of a threat stimulus (a human hand) to cats injected with carbachol caused a significant increase in vocalization. The magnitude of the response was inversely proportional to the physical distance between the cat and the threat stimulus. The hand in motion caused significantly longer vocalization than the immobile hand and cats not familiar with the experimental situation vocalized significantly more than those that had been exposed to the hand before. The spatiotemporal relationship between the animal and the threat stimulus strongly suggests that the carbachol-induced response is emotional and aversive in nature and does not differ from the relevant natural responses.