Oxytocin (OT)


 

Introduction

             Oxytocin is produced by the hypothalamus. It is a peptide hormone (contains 9 amino acids) because it is produced by the hypothalamus, it is also called neuropeptide. Hypothalamus has cell bodies of neurons. The collection of cell bodies are called nuclei. Oxytocin is released by the Paraventricular nucleus (PVM), and Supra optic nerve.
            This hormone is stored in the posterior lobe of the pituitary gland and released from it. It is released in the blood (endocrine hormone or neuroendocrine hormone).

Target

Female; Mammary glands and uterus (endometrium and myometrium).
Male; Tubular genitalia (tail of epididymis, ductus deferens, and ampula).

Function

It is categorized into two functions
  1. Peripheral function (clinically important)
  2. Central function

1. Peripheral functions include

In Female

  • Contraction of smooth muscle in uterus.
  • Contract mammary glands.
  • Milk ejection or milk letdown.
  • Uterine contraction (a. important for parturition and post-partom period, b. involution; decrease in the size of uterus)
  • Acts on the endometrial glands and then endometrial glands produce PGF2a. It will luteolysis (lysis of CL) and the oxytocin for the production of PGF2a comes from CL or CL produces factor (oxytocin) for its own death.

In male

  • Involved in emission during ejaculation.
  • Acts on seminal vesicles; for the production of PGF2a.
  • Erection

 2. Central function

  • It is responsible for the maternal function. For this reason, this hormone is also called the hormone of a cuddle (increase cuddle).
  • Responsible for social behavior. It increases trust and reduces fear. For this reason, this hormone is also known as the hormone of Love.
  • Responsible for sexual behavior. Involved in erection and ejaculation.
  • The level of oxytocin is high after orgasm in both males and females.

Clinical uses of Oxytocin

In female

  • It is used to induce milk letdown.
  • If the uterus does not contract properly during parturition then we use it for the contraction of the uterus.
  • Used for the retained placenta removal.
  • It is used to decrease the chances of uterine prolapse.
  • It is used to enhance uterine involution.
  • It is used for the medical management of dystocia in bitch.
  • It is used for the induction of parturition in mare (all females of the equine family).

In male

In the male, its use is rare.
  • It is used to increase the number of spermatozoa in the first ejaculation but it does not increase the daily sperm production.

Release of OT

Most of the time it is released by the sensory stimulus under the influence of CNS.

Inhibition of OT

It is inhibited by epinephrine, nor-epinephrine, high level of cortisol, during peak estrus/heat, disturbed milking, and during the very early postpartum period.

OT abuse

Excessive milk letdown.

Side effects of OT

  1. It increases the chances of mastitis.
  2. Stimulates endometrial glands ( for the release of PGF2a), if the animal is pregnant, it will cause luteolysis, and also disturb the cycle.  Disturb pregnancy (decreases the rate of pregnancy).
  3. Its continuous action on the endometrial glands will exhaust the glands and they will degenerate. This will cause embryonic death.
  4. It causes cyst formation in fimbriae and endometrium.

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