Abstract
Summary
Daily injections into rats of 2.5 mg pargyline or 2 μg LSD/100 g body weight completely inhibited growth of DMBA–in–duced mammary adenocarcinomas, whereas daily treatment with haloperidol resulted in rapid stimulation of tumor growth as evidenced by a severalfold increase in tumor size and number compared to the controls. On termination of treatment with the 3 drugs, there was a complete reversal of the tumor growth patterns observed during treatment. A rapid increase in tumor size and number occurred in the groups previously given pargyline and LSD, but a marked retardation of tumor growth was observed in the rats previously given haloperidol. These effects of pargyline, LSD and haloperidol on mammary tumor growth are believed to reflect the changes produced by these drugs on pituitary prolactin release. Pargyline and LSD decrease serum prolactin levels whereas haloperidol increases serum prolactin values. The present study provides further evidence that prolactin is essential for growth of DMBA–induced mammary cancers in rats.
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