andrologia 32, 7–11 (2000) Accepted: April 22, 1999 Chronic immobilization-induced stress increases plasma testosterone and delays testicular maturation in pubertal rats S. A. Almeida1, S. O. Petenusci2, J. A. Anselmo Franci2, A. A. M. Rosa e Silva1 and T. L. Lamano Carvalho2 1Department of Physiology, Faculty of Medicine of Ribeira ˜o Preto; 2Department of Morphology, Stomatology and Physiology, Dental School of Ribeira ˜o Preto, University of Sa ˜o Paulo, SP, Brazil Key words. Stress—puberty—spermatogenesis—testosterone—LH Summary. We investigated whether chronic secretion of gonadotrophin-releasing (GnRH) and luteinizing (LH) hormones, prolactin (Prl) and sex stress, applied from prepuberty to early puberty, interferes with the spermatogenic and androgenic steroids (for references see Gala, 1990; Knol, 1991; Rivier & Rivest, 1991). testicular functions. Male pubertal rats (40 days old) were immobilized 6 h per day for 15 days. There are comparatively few reports concerning the effects of stress on the spermatogenic process. Plasma concentrations of corticosterone, prolactin and testosterone were significantly augmented fol- Prolonged immobilization of subhuman primates caused degenerative changes of the germinal epi- lowing immobilization, whereas plasma luteinizing hormone decreased and follicle-stimulating hor- thelium and spermatogenesis arrest (Cockett et al., 1970, 1971; Zemjanis et al., 1970) and a short- mone was not altered. Acute immobilization (5 min) increased prolactin and testosterone levels time immobilization of male rats caused complete disappearance of the germ cell population in control rats but caused a significantly higher increase in these hormones when superimposed (Meitner, 1976). A recent study from our laboratory showed on chronic stress. A lower extent of testicular maturation was observed in pubertal rats immobil- decreased spermatogenic and androgenic testicular functions in adult rats submitted to chronic immo- ized from prepuberty. bilization from prepuberty (Almeida et al., 1998). The purpose of the present study was to investigate whether the same protocol of aversive stimulation, Introduction applied from prepuberty, interferes with the onset of puberty. In addition to the spermatogenic and A diversity of aversive stimuli (ether exposure and surgical procedures, electric-shock, cold water androgenic status, plasma levels of Prl and gonado- tropic hormones were also measured. The stress swimming, capture of wild animals, exposure to a novel environment, noise, immobilization), applied condition of disturbed animals was analysed in terms of plasma corticosterone. To investigate to animal models on a short- or long-term basis, have been used to investigate the response of the whether responsiveness changed with repeated exposure to the stressor, some of the stressed and hypothalamic–pituitary–adrenal and/or hypothal- amic–pituitary–gonadal axis to stress. The stress- control rats were submitted to 5 min of immobiliz- ation shortly before sacrifice. related hormones (corticotrophin-releasing factor, adrenocorticotrophin and adrenal corticosteroids) modulate the effects of stress on male reproductive functions by interfering with the hypothalamic– Materials and methods pituitary–gonadal axis, with a consequently altered Prepubertal (40-day-old) male Wistar rats were used. Groups of four animals were caged together Correspondence: Dra. Teresa L. Lamano Carvalho, in plastic boxes (40 cm×32 cm×17 cm) under Faculdade de Odontologia de Ribeira ˜o Preto, Av. Cafe ´ s/n, 14040–904 Ribeira ˜o Preto-SP, Brasil. controlled environmental conditions (12 h light U.S. Copyright Clearance Center Code Statement: 0303-4569/00/3201-0007 $15.00/0