The reproductive process requires the coordinated action of a large variety of
peptides and steroid hormones, each one playing an important role in the normal
functioning of the reproductive organs. In male bats, this control is linked to the correct
functioning of the hypothalamic-pituitary-testicular axis, combined to the paracrine
communication between Sertoli, Leydig and germ cells. The hypothalamus produces
and secretes gonadotropin-releasing hormone (GnRH), which acts on the pituitary
gland stimulating the production of follicle-stimulating hormone (FSH) and luteinizing
hormone (LH). Both hormones act directly on the testicular somatic cells in order to
stimulate and regulate their function and to control the spermatogenesis process.
Testicular steroids (androgens and estrogens) in turn stimulate the seminiferous tubules
and all secondary sex structures (epididymis and reproductive accessory glands, mainly
the prostate), as well as provide feedback to the hypothalamus and pituitary. The
hormonal regulation of bats differs interspecifically, with some species presenting the
typical mammalian pattern; others showing unique variations, possibly imposed by the
hibernation period; until species that have developed different adaptations, but without
the imposition of a period of hibernation. One of these adaptations is the testicular
regression, which is a deactivation process of the testicular tissue that is triggered by
changes in the pattern of hormonal regulation. Thus, in this chapter, we seek to discuss
different patterns of hormonal regulation of bats and some aspects of testicular
regression.
Keywords: Androgen Receptor, Bat, Chiroptera, Estradiol, Estrogen, Hormonal
Regulation, Reproduction, Spermatogenesis, Testicular Regression, Testis,
Testosterone.
