Increases in plasma catecholamines during naturally elicited defensive behavior in the cat

Defensive behavior was evoked in 12 adult cats by the presentation of both interspecific (barking dog) and intraspecific (hypothalamically stimulated cat) stimuli. Each stimulus was presented 3 times. Concomitant activation of the sympatho-adrenal (SA) system was evaluated by radioenzymatic assay of plasma norepinephrine (NE) and epinephrine (E). The somatic and autonomic displays which accompanied defensive behavior were similar between stimuli, consisting of mydriasis, piloerection, growling, hissing and paw strikes. However, the sympatho-adrenal responses associated with interspecific and intraspecific defensive behaviors were different. Interspecific defensive behavior was accompanied by adrenal medullary release of both NE and E, which decreased with successive trials. Intraspecific defensive behavior was initially associated with release of E from the adrenal medulla; the pattern of catecholamine release in successive trials suggested that in later trials NE was released primarily from the sympathetic nerves. Furthermore, increases in plasma NE and E, as well as increases in heart rate and mean arterial blood pressure during the first trial were significantly greater when the behavioral stimulus was a dog. Although aspects of the feline display to threatening stimuli are stereotyped, the data suggest that the sympatho-adrenal response is more specific, and indicates preparation for fighting or escape.