Role of nitric oxide in animal reproduction: A review

Nitric oxide has emerged as an important regulator of reproductive bio-physiological system and plays a crucial role in reproduction. NO is synthesized from L-arginine by enzyme nitric oxide synthase, which exists in multiple isoforms in a wide range of mammalian cells and implicated in the control of gonadotrophin secretion at both hypothalamic and hypophyseal levels. NO is hypothesized to play a role in steroidogenesis, follicular development and growth, follicular apoptosis, maturation of oocytes, ovulation and luteolysis, and maintenance of pregnancy as well as control of male reproductive functions like spermatogenesis, penile erection, sexual behavior, sperm motility. While considerable work lies ahead in unraveling the role of NO at the peripheral, cellular and molecular level in the domestic animal reproduction, findings with presented in this review provide a general overview of growing appreciation of NO as a vital molecule controlling hypothalamic– pituitary–gonadal (HPG) axis. Further investigations are warranted to explore the role and modulations of NO under normal and abnormal reproductive conditions in domestic animals.