Cervical stimulation activates A1 and locus coeruleus neurons that project to the paraventricular nucleus of the hypothalamus

Abstract

In female rats, stimulation of the uterine cervix during mating induces two daily surges of prolactin. Inhibition of hypothalamic dopamine release and stimulation of oxytocin neurons in the paraventricular nucleus (PVN) are required for prolactin secretion. We aim to better understand how stimulation of the uterine cervix is translated into two daily prolactin surges. We hypothesize that noradrenergic neurons in the A1, A2, and locus coeruleus (LC) are responsible for conveying the peripheral stimulus to the PVN. In order to determine whether projections from these neurons to the PVN are activated by cervical stimulation (CS), we injected a retrograde tracer, Fluoro-Gold (FG), into the PVN of ovariectomized rats. Fourteen days after injection, animals were submitted to artificial CS or handling and perfused with a fixative solution. Brains were removed and sectioned from the A1, A2, and LC for c-Fos, tyrosine hydroxylase (TH), and FG triple-labeling using immunohistochemistry. CS increased the percentage of TH/FG+ double-labeled neurons expressing c-Fos in the A1 and LC. CS also increased the percentage of TH+ neurons expressing c-Fos within the A1 and A2, independent of their projections to the PVN. Our data reinforce the significant contributions of the A1 and A2 to carry sensory information during mating, and provide evidence of a functional pathway in which CS activates A1 and LC neurons projecting to the PVN, which is potentially involved in the translation of CS into two daily prolactin surges.

Preeclampsia is caused by continuous sympathetic center excitation due to an enlarged pregnant uterus

“…have waited for the answer to this question for 60 years after my own report on stimulation of the sympathetic zone. Indeed, recent studies report the presence of nerve fibers between the uterus and hypothalamus [2,[8][9][10], which enabled the conduction of stimuli caused by the enlarged uterus to the sympathetic center located in the hypothalamus during the late stage of pregnancy. In addition, general stress caused by the enlarged uterus may support the excitation of the general sympathetic system.…”

Uterine Contractions in Normal Labor Developed by a Positive Feed-back and Oscillation

“…The developmental mechanism of electrical oscillation is a positive feed-back process in an electronic circuit composed of an amplifier and a positive feedback loop (Figure 4), where the electrical output is Since a labor contraction of uterus is a biological oscillation, a positive feed-back system is adopted to produce regular oscillation, where the amplifier is composed of the contraction promoting system, including hypothalamic nerve center, hypophysis and oxytocin secretion. The contraction amplifying system output is uterine contraction, and the contraction information is fed back to the input of the contraction promoting system through the innervations between the uterus and hypothalamus [6][7][8][9] (Figure 5). The frequency of oscillation developed by the biological positive feed-back system is approx.…”

A Proposal to Reduce Congenital Cerebral Palsy

“…Since a labor contraction of uterus is a biological oscillation, a positive feed-back system is adopted to produce regular oscillation, where the amplifier is composed of the contraction promoting system including hypothalamic center, hypophysis and oxytocin secretion. The contraction amplifying system output is uterine contraction, and the contraction information is fed back to the input of the contraction promoting system through the innervations between the uterus and hypothalamus [6][7][8][9][10] (Figure 5). The frequency of oscillation developed by the biological positive feed-back is approx.…”