State dependence of noradrenergic activity in a rapidly cycling bipolar patient

Plasma levels of the major norepinephrine (NE) metabolite, 3-methoxy-4-hydroxyphenylglycol (MHPG), were measured in a rapidly cycling bipolar patient and her first-degree relatives. The mood state dependence and the reciprocal relationship between noradrenergic and cholinergic activity were investigated by assessing mood, thought disorder, and plasma MHPG following the infusion of physostigmine. A correlation was found between plasma MHPG and mood states, with exceedingly high levels during mania and hypomania. Levels were significantly decreased by ECT or combined lithium and chlorpromazine administration. A pathologic diurnal MHPG pattern was detected during periods of abnormal mod mood changes. Infusion of physostigmine led to a prompt reduction in MHPG release and a marked decline in mood-state measurements and the overall level of thought disorder. Muscarinic receptors exerting negative feedback control over the synthesis and/or release of NE may have become supersensitive as a consequence of α₂-adrenoceptor desensitization.