A peptide has been isolated from ovine hypothalamus which, at 1 x 10(-9)M, inhibits secretion in vitro of immunoreactive rat or human growth hormones and is similarly active in vivo in rats. Its structure is H-Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys-OH The synthetic replicate is biologically active.

https://science.sciencemag.org/content/sci/179/4068/77.full.pdf

Hypothalamic Polypeptide That Inhibits the Secretion of Immunoreactive Pituitary Growth Hormone

Prolactin is a protein hormone of the anterior pituitary gland that was originally named for its ability to promote lactation in response to the suckling stimulus of hungry young mammals. We now know that prolactin is not as simple as originally described. Indeed, chemically, prolactin appears in a multiplicity of posttranslational forms ranging from size variants to chemical modifications such as phosphorylation or glycosylation. It is not only synthesized in the pituitary gland, as originally described, but also within the central nervous system, the immune system, the uterus and its associated tissues of conception, and even the mammary gland itself. Moreover, its biological actions are not limited solely to reproduction because it has been shown to control a variety of behaviors and even play a role in homeostasis. Prolactin-releasing stimuli not only include the nursing stimulus, but light, audition, olfaction, and stress can serve a stimulatory role. Finally, although it is well known that dopamine of hypothalamic origin provides inhibitory control over the secretion of prolactin, other factors within the brain, pituitary gland, and peripheral organs have been shown to inhibit or stimulate prolactin secretion as well. It is the purpose of this review to provide a comprehensive survey of our current understanding of prolactin's function and its regulation and to expose some of the controversies still existing.

/pdf/prolactin-structure-function-and-regulation-of-secretion-3w4x6fqbg3.pdf

Prolactin: Structure, Function, and Regulation of Secretion

Two hours following intraperitoneal injection, estradiol-H3 is concentrated by cells in a system of limbic and hypothalamic structures. Preoptic-hypothalamic nuclei containing estrogen-concentrating cells include the medial preoptic area, medial anterior hypothalamus, ventromedial nucleus, arcuate nucleus and ventral premammillary nucleus. Limbic structures include the medial and cortical nuclei of the amygdala, lateral septum, bed nucleus of the stria terminalis, diagonal band of Broca, olfactory tubercle, ventral hippocampus, and prepiriform and entorhinal cortex. Labelled cells were also found in the lateral and ventrolateral portions of the mesencephalic central grey. Compared to these regions, most other regions of the nervous system, including the spinal cord, have very small numbers of labelled cells, which are relatively weakly labelled, and are not found in regular, specific locations. The distribution of estrogen-concentrating cells determined with the present autoradiographic method agrees with previous autoradiographic conclusions and with biochemical results from cell fractionation experiments.

The locations of estrogen-concentrating cells coincide in several brain regions with locations of estrogen-dependent neuroendocrine control mechanisms, as determined by brain implants, lesions, electrical stimulation, and electrophysiological recording. Moreover, experimental neuroanatomical studies have provided evidence for several pathways connecting regions which concentrate radioactive estradiol. Taken together, the evidence suggests a limbic-hypothalamic system of estrogen-concentrating neurons which participate in the control of mating behavior and of gonadotrophin release from the pituitary.

Atlas of estradiol-concentrating cells in the central nervous system of the female rat.

In September 2006, members of the Sex, Gender and Pain Special Interest Group of the International Association for the Study of Pain met to discuss the following: (1) what is known about sex and gender differences in pain and analgesia; (2) what are the "best practice" guidelines for pain research with respect to sex and gender; and (3) what are the crucial questions to address in the near future? The resulting consensus presented herein includes input from basic science, clinical and psychosocial pain researchers, as well as from recognized experts in sexual differentiation and reproductive endocrinology. We intend this document to serve as a utilitarian and thought-provoking guide for future research on sex and gender differences in pain and analgesia, both for those currently working in this field as well as those still wondering, "Do I really need to study females?"

Studying sex and gender differences in pain and analgesia: a consensus report

In this article, Axelrod applied signal transduction theory to his research on the metabolic function of serotonin, even describing
 the pineal gland as a "neurochemical transducer."

https://science.sciencemag.org/content/sci/184/4144/1341.full.pdf

The pineal gland: a neurochemical transducer.

Normal male rats were subjected to a variety of stress stimuliincluding simple handling, transfer from room to room, ether anesthesia alone or combined with bleeding, the injection of saline or epinep

The Effects of Acute Stress on the Secretion of LH, FSH, Prolactin and GH in the Normal Male Rat, with Comments on Their Statistical Evaluation

Progesterone injected sc into spayed rats primed two days earlier with 5 μg estradiol benzoate increased plasma levels of LH and FSH 6 hr later as measured by radioimmunoassay (RIA). These peaks of plasma LH and FSH were abolished by prior treatment with phenoxybenzamine or haloperidol, while the P-adrenergic receptor blocker, propranolol, had no effect. The results indicated the involvement of an β-adrenergic receptor mechanism and catecholamines (CA) in the transmission of the progesterone stimulus. Drugs which modify brain CA levels were used to identify the CA involved. They were administered prior to the injection of progesterone. The expected peak levels of plasma LH and FSH failed to occur in rats treated with DL-β-methylp-tyrosine methyl ester HC1 (β-MPT) which lowers brain dopamine (DA) and norepinephrine (NE) levels. Sodium diethyldithiocarbamate (DDC) and l-phenyl-3-(2-thiazolyl)-2 thiourea (U-14,624), which are known to decrease NE levels without decreasing DA levels by inhibiting the activity...

Involvement of Norepinephrine in Transmission of The Stimulatory Influence of Progesterone on Gonadotropin Release11

The effects of single sc injections of various doses of estradiol benzoate (Eb) and testosterone propionate (Tp) on plasma levels of LH, FSH and prolactin have been reinvestigated in castrate rats of both sexes. Our results indicate that Eb or Tp inhibited release of LH in castrate rats of both sexes. Males were more sensitive to the inhibitor effect of the low dose of Tp than females. The steroids also lowered plasma FSH levels in spayed females; however, in castrated males Eb stimulated FSH release and a decrease in FSH followed the injection of only the highest dose (2 mg) of Tp. Eb and Tp had a synergistic effect in inhibiting FSH release in the male. Both steroids stimulated release of prolactin in castrate males and females (no sex difference in release of prolactin in response to Eb was observed; however, males appeared more sensitive to Tp treatment). Single injections of progesterone (P) in spayed females produced variable results. High doses inhibited LH release and elevated prolactin levels. Ef...

The EflFects of Gonadal Steroids on Plasma Gonadotropins and Prolactin in the Rat1

DL-α-Methyltyrosine (α-MT), which blocks catecholamine biosynthesis, produced a dramatic rise in plasma prolactin within 30 min of ip injection in castrated rats and treatment with α-MT for 4 days resulted in continued high levels of plasma prolactin and an elevation of pituitary prolactin concentration and content. Plasma FSH and LH were not significantly altered by α-MT. Selective blockade of norepinephrine (NE) biosynthesis with diethyldithiocarbamate (DDC) failed to alter prolactin levels but did lower plasma LH. Blockade of serotonin biosynthesis with p-chlorophenylalanine (p-CPA) failed to modify plasma levels of any of the 3 pituitary hormones measured and did not alter the elevation in plasma prolactin produced by concomitant administration of α-MT. When L-dihydroxphenylalanine (L-DOPA) was administered to elevate brain catecholamines, it lowered plasma prolactin but failed to alter FSH and LH levels. This lowering of piolactin by L-DOPA still occurred if conversion of dopamine (DA) to NE was bloc...

Effects of drugs that modify brain monoamine concentrations on plasma gonadotropin and prolactin levels in the rat.

Serum levels of FSH, LH and prolactin were determined during development in male rats. Blood was collected from the trunk after decapitation. Prolactin levels were very low at 15 and 20 days of age, underwent an initial rise at 25 days, and then remained relatively constant until 50 days. A secondary increase occurred thereafter to reach maximal adult values at 90 days. Serum FSH was readily detectable at 15 and 20 days, rose to a peak at 25 and 30 days and then declined back to the original levels by 60 days. It remained relatively constant thereafter. On the other hand, serum LH levels underwent a very gradual increase from 15 days to reach a maximum at 70 days which was similar to levels found in adults. Initiation of the rapid phase of testicular growth at 25 days could be correlated with the elevations of serum FSH and prolactin levels. Rapid growth of sex accessories began somewhat later in the presence of continued relatively high prolactin levels and falling levels of FSH. Later growth of the sex ...

L. Krulich

Papers

The Effects of Acute Stress on the Secretion of LH, FSH, Prolactin and GH in the Normal Male Rat, with Comments on Their Statistical Evaluation

Involvement of Norepinephrine in Transmission of The Stimulatory Influence of Progesterone on Gonadotropin Release11

The EflFects of Gonadal Steroids on Plasma Gonadotropins and Prolactin in the Rat1

Effects of drugs that modify brain monoamine concentrations on plasma gonadotropin and prolactin levels in the rat.

Changes in Serum Prolactin and Gonadotropins During Sexual Development of the Male Rat