Testicular Function After Local Injection of 6‐Hydroxydopamine or Norepinephrine in the Golden Hamster (Mesocricetus auratus)
Authors: MAYERHOFER ARTUR , AMADOR ARMANDO G. , STEGER RICHARD W. , BARTKE ANDRZEJ 
Published: October 2023

Although there is evidence for the sympathetic innervation of the mammalian testis, the function of noradrenergic fibers is not understood. This in vivo and in vitro study in the adult golden hamster examines testicular function after unilateral intratesticular application of a single dose of 6‐hydroxydopamine (6‐OHDA), a neurotoxic drug known to produce depletion of noradrenergic stores in nerve endings. The contralateral testis in each animal was injected with vehicle alone and served as the control. After 24 h, the content of norepinephrine (NE) in testicular parenchyma was reduced in most testes injected with 6‐OHDA. At this time, concentration of luteinizing hormone receptors (LH‐R) was significantly decreased in the 6‐OHDA treated testis, compared with the vehicle‐injected testes. This decrease was followed by a significant increase at 72 h. The concentration of LH‐R was not significantly altered 10, 48, 144, or 168 h after 6‐OHDA administration. Changes in testicular testosterone (T) concentrations paralleled the changes in LH‐R at most time points. In the incubations of control vehicle injected testes, addition of NE did not affect T production but stimulatory action of hCG was significantly augmented by concomitant exposure to NE at most time points after injection of vehicle. In incubations of 6‐OHDA‐injected testes, a comparable pattern of T responses to NE and hCG was found only 48 h after injection. At 24 h post injection NE alone significantly stimulated T production; at 10 and 24 h the ability of NE to potentiate the action of hCG was significantly reduced, while at 72 and 144 h basal T production and the stimulatory hCG effect were significantly increased. Moreover, at 72, 144, and 168 h, the effect of NE & hCG on T production was significantly greater in 6‐OHDA‐injected testes than in the vehicle injected testes of the same animals. In incubations of untreated hamster testes, addition of 6‐OHDA at doses similar to those used for injections did not affect T production. Weights of 6‐OHDA injected testes were slightly but significantly reduced after 144 and 168 h. These changes were most likely due to degenerative changes of the germinal epithelium, which were clearly detectable 168 h post injection. Because 6‐OHDA can release NE from nerve terminals, the observed effects of 6‐OHDA might have been initiated by supernormal testicular NE concentrations. To examine this possibility, the authors have tested the effects of intratesticular NE injections. This treatment caused decrease of LH‐R at 24 h followed by an increase at 72 h. Testicular T concentrations were significantly reduced 24 h post NE injection and numerically increased 72 h after NE injection, when compared to the values obtained from vehicle injected testes from the same animals. The weights of the NE injected testes were significantly reduced after 72 h. Thus, unilateral intratesticular administration of 6‐OHDA and NE can influence testicular function in hamsters by regulating LH‐R. These findings suggest a novel role for catecholamines and noradrenergic nerves in the control of testicular function. Involvement of these effects in suppression of testicular function during stress can be suspected.