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8-OH- DPAT (8-hydroxy-2-[di-n-propylamino] tetralin) is a novel aminotetralin derivative which has been proposed to be a serotonin (5-HT) agonist devoid of dopamine agonist effects. We now report that the administration of 8-OH- DPAT , like known 5-HT agonists, produced a rapid elevation of serum prolactin concentrations in male rats. The prolactin response to 8-OH- DPAT , like that induced by other 5-HT agonists, was greatly potentiated in animals pretreated with the tryptophan hydroxylase inhibitor, para-chlorophenylalanine. However, the 8-OH- DPAT -induced elevation of serum prolactin concentrations in untreated rats was not dose-dependent and was modest in magnitude compared to that produced by known 5-HT agonists. In contrast to the stimulatory effects of 8-OH- DPAT on prolactin secretion in vivo 8-OH- DPAT suppressed the secretion of prolactin from anterior pituitary tissue in vitro, and this effect was blocked by haloperidol. The results of the present study are supportive of the view that 8-OH- DPAT has dopamine agonist, as well as 5-HT agonist, properties.

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Skeletal muscle tissue was obtained from the vastus lateralis or peroneus brevis muscles of 34 healthy volunteers. Focal and extensive areas of Z band streaming and disruption of myofibrillar architecture without Z band streaming were quantified in Araldite-embedded specimens examined in the phase microscope. Extensive areas of Z band streaming in more than 2.0 percent of fibers was present in only two of the 34 volunteers. Myofibrillar disruptions without Z band streaming was much less common than Z band streaming. The size of extensive areas of Z band streaming or myofibrillar disruptions was quantified by counting the number of adjacent fibrils and contiguous sarcomeres occupied by either type of lesion. These data should be of use in determining if such lesions are present in excessive amounts in suspected pathologic material.

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