Pharmacology of 6,7-dihydroxy-2-dimethylaminotetralin (TL-99). I. Cardiovascular activity in the dog and cat.

6,7-Dihydroxy-2-dimethylaminotetralin (TL-99), the 5,6-dihydroxy isomer (M-7) and dopamine were studied for cardiovascular activity in the cat and dog. TL-99 was found to be the most active of these compounds. Some of the more striking actions of TL-99 and M-7 were bradycardia, hypotension and complete blockade of norepinephrine-induced reflex activation. A detailed study of these compounds showed that they were most likely exerting their effects by inhibiting sympathetic nervous system activity. Whether these compounds were activating dopamine receptors or alpha adrenergic receptors is not entirely clear from this study.