Brain And Skin Blood Flow: New Animal Model For Understanding Psychiatric Disorders And Evaluating Psychotropic Agents
Funder
National Health and Medical Research Council
Funding Amount
$874,840.00
Summary
We suddenly become pale when we get a fright; cutaneous blood vessels are linked to psychological function. The skin vessel constriction response occurs because special neurochemical pathways in the brain send messages to the spinal cord, and from there messages traverse peripheral sympathetic nerves to constrict the blood vessels in the skin. By measuring skin blood flow in the rabbit ear and the rat tail we have been able to discover the major brain pathway by which the constrict-the-skin-bloo ....We suddenly become pale when we get a fright; cutaneous blood vessels are linked to psychological function. The skin vessel constriction response occurs because special neurochemical pathways in the brain send messages to the spinal cord, and from there messages traverse peripheral sympathetic nerves to constrict the blood vessels in the skin. By measuring skin blood flow in the rabbit ear and the rat tail we have been able to discover the major brain pathway by which the constrict-the-skin-blood-vessels message reaches the spinal cord. The pathway involves the amygdala, a forebrain region important in emotional expression and the raphe nuclei in the medulla oblongata. Drugs which affect psychological function also effect skin blood flow. Ecstasy, the street drug used to induce euphoria also constricts the skin vessels, and, sadly, the body temperature may increase so much that death ensues. Ecstasy vigorously constricts the skin blood vessels in rabbits, and temperature increases. Ecstasy is thought to act on serotonin-containing nerve cells in the brain, releasing serotonin (5-HT) onto special 5-HT2A receptors. Activation of these receptors affects both psychological function and skin blood flow. Modern drugs used to treat schizophrenia, so called atypical antipsychotics like clozapine and olanzapine, are thought to act as antagonists at 5-HT2A receptors in the brain. We were thus very excited when we discovered in our rabbit model that clozapine reverses the skin vasoconstriction induced by ecstasy. This means that we have specific hypotheses concerning the actual brain pathways and neurotransmitters whereby ecstasy and clozapine exert their effects on skin blood flow. Elucidating these pathways in rabbits and rats will provide solid knowledge concerning the mechanism of action of the atypical antipsychotics, and it may well prove possible to use our animal model to predict whether proposed new antipsychotic agents will be therapeutically effective.Read moreRead less
Pathways For Estrogen Feedback To Gonadotropin Releasing Hormone Neurons
Funder
National Health and Medical Research Council
Funding Amount
$466,980.00
Summary
Gonadotropin releasing hormone (GnRH) is the brain hormone that drives the reproductive process. In the female, a surge in the secretion of GnRH is the trigger for ovulation. An understanding of the mechanisms that regulate the secretion of GnRH is, therefore, extremely important if we are to decipher abnormalities that lead to infertility. Understanding of the ovulatory process is also important for the development of new (possibly simpler) means of contraception. Our research is intended to pr ....Gonadotropin releasing hormone (GnRH) is the brain hormone that drives the reproductive process. In the female, a surge in the secretion of GnRH is the trigger for ovulation. An understanding of the mechanisms that regulate the secretion of GnRH is, therefore, extremely important if we are to decipher abnormalities that lead to infertility. Understanding of the ovulatory process is also important for the development of new (possibly simpler) means of contraception. Our research is intended to provide a full understanding of the brain circuits that provide input to the GnRH neurons. In particular, we will focus on the microcircuitry in the preoptic area, where GnRH cells are found. In addition to providing a full understanding of the circuits that are primarily involved in regulating GnRH secretion, this work will provide a substrate upon which we can expand knowledge of how factors such as emotion and stress can impact on the reproductive process.Read moreRead less
Functional Modulation Of Ovine And Human Somatotropes By In Vitro Application Of Leptin
Funder
National Health and Medical Research Council
Funding Amount
$227,036.00
Summary
Obesity is a common disorder in developed countries and a prevalent condition which is often stigmatized. Actuarial data indicate that life expectancy is reduced when body-mass index (body mass in kg-square of the height in metres) is 20% or more above the ideal (obesity is >28% above ideal). Growth hormone (GH) from pituitary gland is the major anabolic hormone to increase muscle and reduce fat. A significant reduction in GH is found in obesity. Indeed, visceral fat mass is primary negative ....Obesity is a common disorder in developed countries and a prevalent condition which is often stigmatized. Actuarial data indicate that life expectancy is reduced when body-mass index (body mass in kg-square of the height in metres) is 20% or more above the ideal (obesity is >28% above ideal). Growth hormone (GH) from pituitary gland is the major anabolic hormone to increase muscle and reduce fat. A significant reduction in GH is found in obesity. Indeed, visceral fat mass is primary negative statistical determinant of GH secretion in middle age men and women. It is clear that the reduction in GH is due to a low sensitivity of GH cells to GH-releasing hormone (GHRH) from brain. It is therefore necessary to understand the change of pituitary GH cells in obesity. A recently identified, fat cell secreted, polypeptide (leptin) is demonstrated to reduce food intake and increase energy expenditure. Receptors for leptin have been found in pituitary gland, mainly in GH secreting cells. In our preliminary experiments, leptin reduces GH secretion by decreasing GHRH receptor synthesis. Meanwhile, this leptin treatment increased the receptors for GH-releasing peptide (GHRP), a synthetic peptide stimulating GH secretion. We aim to investigate the effect of leptin on cultured ovine and human GH cells by studying important cell functions including hormone and receptors synthesis, intracellular signaling molecules, membrane ion channels and cellular secreting machinery. The results will clarify the mechanism underlying GH deficiency in obese patients. We will also test the effect of synthetic GHRP in combination with leptin in vitro. The relationship between GHRP and leptin on the functional modification of GH cells will also be studied. It is likely to see that GHRP reduces the inhibitory effect of leptin on GH cells. This may end up an effective therapeutical use of GHRP (oral available) in the treatment of obesity.Read moreRead less
Neuroendocrine Functions Of PrRP, A Novel Hypothalamic Peptide
Funder
National Health and Medical Research Council
Funding Amount
$183,928.00
Summary
This project investigates the role of a newly discovered chemical (peptide) that is found in a part of the brain called the hypothalamus which regulates the activity of the pituitary gland. The hypothalamus and pituitary gland work together to control many of the body?s essential processes such as growth, metabolism and reproduction. Some human diseases are caused by abnormalities of the hypothalamus and pituitary gland while many other diseases affect the functions of these glands, leading to w ....This project investigates the role of a newly discovered chemical (peptide) that is found in a part of the brain called the hypothalamus which regulates the activity of the pituitary gland. The hypothalamus and pituitary gland work together to control many of the body?s essential processes such as growth, metabolism and reproduction. Some human diseases are caused by abnormalities of the hypothalamus and pituitary gland while many other diseases affect the functions of these glands, leading to widespread complications such as weight loss, wasting, abnormal immune responses, infertility or failure of lactation. While many of the hormones and chemicals of the hypothalamus and pituitary gland have been extensively studied, recent advances in molecular biology have led to the discovery of new chemicals that may have important regulatory functions. One of these newly discovered substances which was named Prolactin-Releasing Peptide or PrRP is the topic of this project. PrRP will be tested in a series of experiments in animals in order to determine how important it is in regulating the pituitary gland, particularly in stress and during lactation which are conditions when PrRP could be secreted. It is hoped that this research will lead to a more detailed understanding of how the reproductive and endocrine system are controlled in humans and to new methods for the manipulation of these systems under normal and disease conditions.Read moreRead less