Gp. Hamlin et al., Hormonal variation of rat uterine contractile responsiveness to selective neurokinin receptor agonists, BIOL REPROD, 62(6), 2000, pp. 1661-1666
Regulated uterine contractions are important in many reproductive functions
such as sperm transport and embryo positioning during implantation The rol
e of classical neurotransmitters including acetylcholine and norepinephrine
in regulating myometrial contractility has been well studied; however, the
peripheral role of sensory neurotransmitters such as the neurokinins is le
ss clear The major neurokinins are substance P, neurokinin A, and neurokini
n B, which predominantly activate neurokinin receptors (NK-Rs) 1, 2, and 3,
respectively. This study utilized selective receptor agonists to examine t
he role of NK-Rs in uterine contractility. Uterine tissues, obtained from t
he major stages of the rat estrous cycle, were stimulated with selective NK
-R agonists. Addition of each agonist resulted in a significant contractile
response. However, the magnitude and nature of the response were dependent
upon the stage of the estrous cycle, with responses to all agonists being
significantly decreased in tissue from proestrus and estrus. Furthermore, t
he nature of NK3-R-mediated contraction was different in tissue from proest
rus and estrus compared to metestrus and diestrus. The hormonal dependence
of NK-R-mediated contractility was then examined in the ovariectomized estr
ogen-supplemented rat model. These studies confirmed that the magnitude and
nature of uterine contractility in response to NK-R activation depend upon
the hormonal environment.