SUMMARY:The aim of the present study was to test the hypothesis that the application of fluoxetine -a highly selective serotonin reuptake inhibitor (SSRI) -in rats during the suckling period induces changes in testicular development. Groups of newborn male rats were randomly assigned with different doses of fluoxetine 24 hours after birth. Each litter stayed with its respective mother during 21 days. Body weight (BW) was measured daily from the 1st -21 st day to calculate daily doses of fluoxetine. 5 mg (T1), 10 mg (T2) 20 mg (T3) or deionized water, were injected intraperitoneally. On the 21 st day, animals were heparinized, anesthetized and blood was collected by cardiac puncture to determine by radioimmunoassay the follicle stimulating hormone (FSH) levels. Testis were removed, weighed, and processed for morphometric analysis. Fluoxetine groups presented decreased body and testicular weight when compared with the control group on the 21 st day. Our findings show that the manipulation of the serotoninergic system with fluoxetine during the critical period of testicular development alters the Sertoli cell population and all testicular parameters related to this cell.

-Endogenous opioid peptides play an important role in the ontogenesis of the functional and morphological parameters of the seminiferous epithelium. The aim of this study was to evaluate the effects of neonatal manipulations with naloxone, an opioid antagonist, on the population of Sertoli cells and on sperm production in adult rats. Rats were assigned to receive 8 µg per gram of body weight twice a day with interval of 8 h of naloxone and they were compared to a control group receiving saline. Naloxone groups presented the following findings when compared to the control group: increased body weight from the 2nd to the 27th day; a smaller seminiferous epithelium height, smaller seminiferous tubule diameter, increased number of Sertoli cells and daily sperm production per testis, increased daily sperm production per gram per testis and increased total length of the seminiferous tubule of the treated groups. According to our study, the neonatal treatment with naloxone during the critical period of testis development was able to change the proliferative dynamics of Sertoli cells by an intra and/or extra testicular blockage of opioid receptors, confirming the direct relation between the number of Sertoli cells and the number of spermatozoids. naloxone / testis development / Sertoli cells / sperm production / rats

In current assay the serotoninergic system in newly-born Wistar rats underwent pharmacological modification by fluoxetine, a selective serotonin reuptake inhibitor (SSRI), to investigate its repercussion on testicular parameters in adult animals. Thirty animals were distributed according to treatment: control animals (n = 6), animals treated with 1 mg kg -1 (n = 6), 5 mg kg -1 (n = 6), 10 mg kg -1 (n = 6) and 20 mg kg -1 (n = 6) of fluoxetine (IP). When 150 days old, the animals were anesthetized and perfused intra-cardiacally with fixative solution. Testes were routinely processed for inclusion in plastic resin (methacrylate glycol). Further, 4 μm-thick histological sections were stained with toluidine blue/sodium borate 1% and analyzed histometrically. Pharmacological intervention on the serotoninergic system during the postnatal period of the testes development in Wistar rats with fluoxetine chlorohydrate reduced parameters, such as testicular weight, testis liquid weight and seminiferous tubules diameter. However, testicular parameters, such as daily sperm production (DSP), spermatogenesis efficiency (DSP/g/testis) and cell population in stage VII of adult animals, were not influenced by fluoxetine chlorohydrate usage during neonatal period. Results show that administration of fluoxetine during 21 days after birth may induce adverse changes in the spermatogenesis of adult rats.