Depending on the dose 6-OHDA stimulates or inhibits the testis of immature rats.

The effect of the neurotoxic drug, 6-hydroxy-dopamine (6-OHDA) on the testicular growth, the compensatory testicular hypertrophy, the testicular cytology and the serum testosterone level was studied in immature rats. Unilateral injection of 33 micrograms of 6-OHDA beneath the testicular capsule in animals with two testes did not alter the weight of the gonads but promoted the development of both testes. Unilateral injection of 333 micrograms of 6-OHDA resulted in a decreased weight and severe atrophy of the treated gonad, while a significant weight gain of the contralateral testis occurred. In hemicastrated rats 33 micrograms of 6-OHDA into the remaining testis caused an enhanced compensatory testicular hypertrophy. When 333 micrograms of 6-OHDA was administered beneath the capsule of the remaining testis a diminished compensatory testicular hypertrophy occurred but no signs of degeneration could be observed. Data indicate that the testicular adrenergic elements play a role in the testicular growth, in the development of compensatory testicular hypertrophy and in the cytodifferentiation of the immature testis.