Centrally induced feline emotional behavior and limbic kindling

The threshold intensity required for electrical hypothalamic/mesencephalic stimulation to elicit emotional behavior in cats was examined chronologically during limbic kindling (n = 9/5), and without kindling (n = 3/3) for a matching control period. After the completion of primary site amygdaloid (AM) or hippocampal (HIPP) kindling, the hypothalamic defensive behavior threshold showed a +/- 20% fluctuation from the prekindling baseline with a mean tendency for reduction as in the control animals. The flight behavior threshold increased in the kindled animals, and decreased in the controls; however, the degree of change was not statistically significant. In contrast, the mesencephalic defensive behavior threshold, which was quite stable in the controls, decreased significantly upon primary (mean -13.5%) and secondary site (mean -22.2%) AM kindling, whereas the flight and screeching (sound emission) behavior threshold remained unchanged throughout kindling. The decreased or unchanged thresholds for each behavior were independent of the timing of the hypothalamic/mesencephalic stimulation after kindled generalized convulsion. The decreased mesencephalic defensive behavior threshold persisted during a 1- to 3-month rest period without kindling stimulation. These findings suggest that acquisition of feline AM-kindled seizure susceptibility is associated with a lasting facilitation of midbrain (but not hypothalamic) excitability for defensive (but not flight) behavior.