Physiology of Reproduction

Developmental variations in environmental influences including endocrine disruptors on pubertal timing and neuroendocrine control: Revision of human observations and mechanistic insight from rodents

“…2 are shown the species-related differences in relative duration of the prepubertal latency (from birth to puberty) when calculated as a percentage of lifespan for comparison purposes. Ewe (Foster et al, 1985), rat (Maeda et al, 2000) and quail (Ottinger et al, 2003) start puberty after a latency accounting for 4.8-5.7% of the lifespan as opposed to 16.3% in humans (Roelants et al, 2009) and 22.5% in baboons (Onyango et al, 2013) that is about 3-4 times longer than in non-primate species. Another less emphasized species-related difference is the variance of pubertal timing among individuals.…”

“…In the rat, the onset of puberty is marked by an increase in testicular weight increase in males and vaginal opening followed by the first estrus in female rodents and (Maeda et al, 2000). The onset of puberty takes place around the time of weaning by the age of 3 weeks as evidenced from onset of increase in serum levels of gonadal hormones (Maeda et al, 2000). It is preceded by attainment of a pubertal pattern of pulsatile GnRH secretion from hypothalamic explants (Bourguignon and Franchimont, 1984;Bourguignon et al, 1990Bourguignon et al, , 1992.…”

“…Since some data obtained in human, non-human primates and rodents will be discussed with emphasis on neuroendocrine maturation, it is important to keep in mind that when birth takes place in rodents, maturation of the brain is less advanced than in human newborns (Clancy et al, 2007). In the rat, the onset of puberty is marked by an increase in testicular weight increase in males and vaginal opening followed by the first estrus in female rodents and (Maeda et al, 2000). The onset of puberty takes place around the time of weaning by the age of 3 weeks as evidenced from onset of increase in serum levels of gonadal hormones (Maeda et al, 2000).…”

“…The timing of puberty shows important differences between human individuals and the physiological range (3rd to 97th centile) of 4.8 years (Roelants et al, 2009) represents 6.25% of the life span. In the laboratory rat with a life expectancy of 2 years, the timing of puberty varies within 4-5 days (Maeda et al, 2000) accounting for an individual variance of 0.55% which is 11 times less than in humans. In sheep (Foster et al, 1985), and quail (Ottinger et al, 2003), the variance of pubertal timing represents 0.87% and 1.9% of lifespan, respectively, that is also less than in humans (Fig.…”

Naloxone Breeding Effectiveness in Rat Suffering from Nitric Oxide-induced Polycystic Ovary Syndrome

“…Female rats with 4 to 5 days sexual cycle are always in diestrous 13,14 unless they mated with the males. Thus, the rats kept virgin and did not expose to the males, were chosen for studying.…”