Stress-induced facilitation of acoustic startle after d-amphetamine administration.

Administration of d-amphetamine enhanced the startle response to an auditory stimulus. In contrast to saline treated mice, startle activity after amphetamine administration did not wane with repeated exposure to the auditory stimulus. Rather, the effects of amphetamine on startle activity increased as a function of stimulus presentation. Whereas exposure to isolation stress or inescapable shock had no effect on startle activity, both types of stress potentiated the effects of amphetamine on startle arousal. The observation that stress sensitized animals to later amphetamine administration is consistent with the effects of stress on other amphetamine behaviors, e.g., stereotypy. Results were related to the development of dopamine post-synaptic receptor supersensitivity after exposure to stress and were discussed in terms of the role played by stress in the expression of behavioral arousal, in the etiology of schizophrenia.