This study is the first placebo-controlled maintenance versus withdrawal trial of its kind in disruptive behavior disorder and provides evidence that patients who respond to initial treatment with risperidone would benefit from continuous treatment over the longer term.

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SUMMARYThe relationship between plasma levels of norepinephrine (NE) and sympathetic neural activity is discussed with special reference to human primary hypertension. Since sympathetic discharge is differentiated, neural activity to a given target organ will contribute variably to plasma NE levels in different situations. Hemodynamically, early primary hypertension is often characterized by a mild defense reaction-like pattern with signs of increased sympathetic activity to the heart and vasoconstriction in the renal and splanchnic vascular beds. Although important hemodynamically, these organs seem to be ofless importance as contributors to peripheral plasma NE levels. In contrast, muscle sympathetic activity and muscle vascular resistance is unchanged or reduced. Since this organ mass contributes importantly to plasma NE levels, especially in peripheral venous blood, it is not surprising that most patients with primary hypertension have normal NE levels. It is concluded that NE concentrations in forearm or mixed venous blood are unreliable indicators of sympathetic neural contributions to essential hypertension, tending to underestimate this element, and that regional measurements of NE overflow are needed for a reliable analysis. cholamine concentrations in body fluids have reached high sensitivity and accuracy and can for some purposes be a valuable tool, particularly for studies in humans when simple and safe indicators of sympathetic activity are needed. Such measurements have also become widely used for assessing the involvement of neurogenic elements in primary hypertension (recently surveyed by Goldstein 1 -2 ). It should be realized, however, that norepinephrine (NE) is a locally released transmitter, rather than a hormone, and that the autonomic nervous system operates quite differently from hormonal systems. Thus, there are good reasons for considerable caution when interpreting plasma NE levels, particularly in hypertension, as will be outlined below.

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Mild post-traumatic symptoms may accompany paediatric elective surgery and persist for at least 1 month. Parents may also manifest anxiety and depressive symptoms, which may diminish earlier, that is, immediately after the surgery or within 1 month.