Twenty-four hour urinary excretion of 3-methoxy-4-hydroxphaeylglycol (MHPG), the metabolite thought best to reflect brain norepinephrine metabolism, was studied longitudinally in ten depressed patients before and during the acute and chronic phases of lithium treatment. Five of the patients were identified as bipolar I (prior history of mania), 3 as bipolar II (history of hypomania) and 2 as unipolar (history of depression). During acute lithium administration (first week) there was no consistent pattern of change in MHPG. Comparing the predrug period with the third and fourth week of treatment, all of the responders showed an increase in MHPG, while the non-responders showed no change or a decrease. It is concluded that the change in clinical state is the most important variable contributing to MHPG changes in these patients. There was a tendency for the pretreatment MHPG excretion to be low in the patients who went on to show a clear-cut antidepressant response to lithium compared to those who were unequivocal non-responders. The predrug MHPG for the bipolar patients (prior history of mania) was significantly lower than the unipolar patients, a difference which apparently contributes to the lower MHPG in the lithium responders, all of whom were in the bipolar group.

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Ambivalent behavior or ambivalence in rats was observed in a single-lever Skinner box situation. The behavioral features associated with ambivalence were filmed and described, and their intensities were graded. It was found that different behavioral patterns, depending on the site of stimulation, are involved in ambivalence. Moreover, the intensity of self-stimulation and withdrawal was found to be higher in subjects implanted in posterior brain areas than in rats implanted in anterior areas, suggesting the existence of a gradient of ambivalence. At a theoretical level, it was suggested that complex mechanisms, possibly involving an autonomous ambivalent system, could be responsible for ambivalence.

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