Amphetamine acts within the medial basal forebrain to initiate and maintain alert waking

Amphetamine-like stimulants exert well-known arousal-enhancing actions. Sur prisingly, little is known concerning the neuroanatomical substrates throug h which these drugs enhance arousal. Previous work implicates a number of b asal forebrain structures in the regulation of behavioral state. The curren t studies examined the effects of amphetamine infusions made directly withi n basal forebrain sites on behavioral, electroencephalographic, and electro myographic indices of arousal in anesthetized and unanesthetized rat. In th e anesthetized rat, amphetamine elicited prolonged epochs of bilateral elec troencephalographic activation when infused unilaterally (3.75 mu g/150 nl) into an extended region of the medial basal forebrain, demarcated anterior ally by the anterior portion of the medial septal area (which includes post erior accumbens shell) and posteriorally by the posterior aspect of the pre optic area of the hypothalamus. In the unanesthetized (undisturbed, resting ) rat amphetamine infusions into this region elicited prolonged epochs of a lert waking, which at the lowest dose (3.75 mu g), qualitatively resembled normal waking. Infusions placed lateral (including within the substantia in nominata), anterior (including within the core subregion of the nucleus acc umbens), posterior, or dorsal to these structures, as well as directly with in the lateral ventricles did not alter electroencephalographic or behavior al measures. These results indicate that a region of the medial basal forebrain, extendi ng from the anterior medial septum/accumbens shell to the posterior preopti c area, is a site within which amphetamine-like stimulants act to enhance b ehavioral and electroencephalographic measures of arousal. (C) 1999 IBRO. P ublished by Elsevier Science Ltd.