Scientists uncover a difference between the sexes

hippocampus
The hippocampus is a region of the brain largely responsible for memory formation. Credit: Salk Institute

Male and female brains operate differently at a molecular level, a Northwestern University research team reports in a new study of a brain region involved in learning and memory, responses to stress and epilepsy.

Many brain disorders vary between the sexes, but how biology and culture contribute to these differences has been unclear. Now Northwestern neuroscientists have found an intrinsic biological difference between and in the molecular regulation of synapses in the hippocampus. This provides a scientific reason to believe that female and male brains may respond differently to drugs targeting certain synaptic pathways.

"The importance of studying in the brain is about making biology and medicine relevant to everyone, to both men and women," said Catherine S. Woolley, senior author of the study. "It is not about things such as who is better at reading a map or why more men than women choose to enter certain professions."

Among their findings, the scientists found that a drug called URB-597, which regulates a molecule important in neurotransmitter release, had an effect in females that it did not have in males. While the study was done in rats, it has broad implications for humans because this drug and others like it are currently being tested in in humans.

"Our study starts to put some specifics on what types of molecular differences there are in male and female brains," Woolley said.

Woolley is the William Deering Chair in Biological Sciences, professor of neurobiology in the Weinberg College of Arts and Sciences and a member of the Women's Health Research Institute at Northwestern University Feinberg School of Medicine.

The study of inhibitory synapses and , which regulate neurotransmitters, was published today (Aug. 12) in The Journal of Neuroscience. It is the first study to detail where males and females differ in a key molecular pathway in the brain.

"We don't know whether this finding will translate to humans or not," Woolley said, "but right now people who are investigating endocannabinoids in humans probably are not aware that manipulating these molecules could have different effects in males and females."

Specifically, Woolley and her research team found that in female brains the drug URB-597 increased the inhibitory effect of a key endocannabinoid in the brain, called anandamide, causing a decrease in the release of neurotransmitters. In male brains, the drug had no effect. (The difference is not related to circulating reproductive hormones.)

The subject of many clinical trials, endocannabinoids are molecules that help regulate the amount of certain neurotransmitters released at synapses, the gap between neurons. These molecules are involved in a variety of physiological processes including memory, motivational state, appetite and pain as well as in epilepsy, a neurological disorder. (Their name comes from the fact that endocannabinoids activate the same neural receptors as the active ingredient in marijuana.)

Understanding what controls the synthesis, release and breakdown of endocannabinoids has broad implications both for normal and pathological brain function, Woolley said. This study contributes an important piece of knowledge.

For 20 years, Woolley actively avoided studying sex differences in the brain until her own data showed her that differences between females and males were real. Her discovery, reported in 2012, that estrogens decreased inhibitory synaptic transmission in the brains of female rats but not in males, changed her thinking.

"Being a scientist is about changing your mind in the face of new evidence," Woolley said. "I had to change my mind in the face of this evidence."

Building on these earlier findings, Woolley and her team used a series of electrophysiological and biochemical studies to pinpoint what causes this effect. The researchers found the difference between males and females lies in the interaction between the molecules ERalpha and mGluR1. Details of the molecular pathway are reported in the new study.

To find out what is the same and what is different between males and females, scientists need to study both sexes, Woolley maintains. Currently, about 85 percent of basic neuroscience studies are done in male animals, tissues or cells.

"We are not doing women—and specifically women's health—any favors by pretending that things are the same if they are not," Woolley said. "If the results of research would be different in female animals, tissues and cells, then we need to know. This is essential so that we can find appropriate diagnoses, treatments and, ultimately, cures for disease in both sexes."


Explore further

Men and women could use different cells to process pain

More information: "Sex Differences in Molecular Signaling at Inhibitory Synapses in the Hippocampus," The Journal of Neuroscience, 2015.
Provided by Northwestern University
Citation: Scientists uncover a difference between the sexes (2015, August 12) retrieved 17 January 2019 from https://medicalxpress.com/news/2015-08-scientists-uncover-difference-sexes.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
1072 shares

Feedback to editors

User comments

JVK
Aug 12, 2015
http://www.amazon...99737673 p. 210

Simon Le Vay wrote:
"This model is attractive in that it solves the "binding problem" of sexual attraction. By that I mean the problem of why all the different features of men or women (visual appearance and feel of face, body, and genitals; voice quality, smell; personality and behavior, etc.) attract people as a more or less coherent package representing one sex, rather than as an arbitrary collage of male and female characteristics. If all these characteristics come to be attractive because they were experienced in association with a male- or female-specific pheromone, then they will naturally go together even in the absence of complex genetically coded instructions."

The model of sex differences in the hippocampus was included here http://www.hawaii...ion.html

JVK
Aug 12, 2015
http://www.jneuro...abstract

Journal article excerpt: "This suggests that the sex difference in E2 modulation of mGluR1 signaling is a classical "organizational" effect of gonadal hormones, in which early life exposure to E2 or T masculinizes the brain and the lack of E2 or T results in feminization."

Gonadotropin releasing hormone (GnRH) is the source of all downstream epigenetic effects of food odors and pheromones that clearly link the life history transitions of honeybees to humans via differences in RNA-mediated single amino acid substitutions that differentiate all cell types. The epigenetic effects on vertebrate cell type differentiation are genetically predisposed and experience-dependent via associations with exposure to E2 or T.

See: Feedback loops link odor and pheromone signaling with reproduction http://www.ncbi.n...16290036

and http://www.ncbi.n...24693353

JVK
Aug 12, 2015
"I should think we might fairly gauge the future of biological science, centuries ahead by estimating the time it will take to reach a complete comprehensive understanding of odor. It may not seem a profound enough problem to dominate all the life sciences, but it contains, piece by piece, all the mysteries" (p. 732). http://www.nejm.o...73021307

Precision Medicine: Unlocking Biological Mysteries begins in one day.
LIVE WEBCAST DATE: August 13, 2015
LIVE WEBCAST TIME: 02:30 PM EDT

I am amazed by claims that link a single aspect of sex differences in cell types to something that today's researchers consider important because they have ignored the role that food odors and pheromones play in the life history transitions of species from microbes to man.

See also: Pheromones and the luteinizing hormone for inducing proliferation of neural stem cells and neurogenesis http://www.freshp...8009.php

Aug 12, 2015
title is kinda funny, in two ways.

Aug 13, 2015
Wow! Just as I always thought, women and men are different flavors of the same ice-cream.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more