Audiogenic stress response: behavioral characteristics and underlying monoamine mechanisms.

Behavioral characterization of the audiogenic stress response in rats revealed an intensity related multiphasic pattern including an initial, transient activation followed by prolonged periods of response suppression during the remainder of the noise exposure and excitation after noise offset. These observations emphasize the need to consider the temporal proximity between exposure to a stressor and either behavioral characterization and/or determinations of neurochemical changes relevant to the stress response. In a second series of studies, the effect of the NE alpha 2 agonist clonidine and the NE alpha 2 antagonist yohimbine were evaluated on the different components of the audiogenic stress response. The effects of intracerebroventricular xylamine-induced depletion of NE were also examined. The results seem to indicate that CNS noradrenergic systems may not be specifically implicated in regulating the responsiveness to noise stimulation but instead may subserve a more general role in adjusting baseline levels of motoric output in response to environmental conditions.