The TGR5 receptor mediates bile acid-induced itch and analgesia

The liver secretes bile acids to aid in the digestion of fats. Cholestasis is a condition in which the bile flow from the liver to the duodenum is impeded. Patients with the disease exhibit itchiness (pruritis) and cannot sense pain (analgesia). The molecular mechanisms mediating these effects are unknown. Carlos Corvera of UCSF and Nigel Bunnett of Monash University discuss their study demonstrating that bile acids cause itch and analgesia by activating the TGR5 receptor in neurons. Highlights:

• TGR5 is expressed in neurons in mouse dorsal root ganglia and spinal cord, which transmit itch and pain signals.
• Stimulation of TGR5 induced the release of itch and analgesia transmitting molecules, including gastrin-releasing peptide and leucine-enkephalin.
• Intradermal injection of bile acids stimulated scratching behavior that was TGR5-dependent.
• Bile acids activate TGR5 on sensory nerves to transmit itch and analgesia, suggesting that these mechanisms contribute to pruritus and analgesia during cholestatic liver diseases.

Increased brain uptake and oxidation of acetate in heavy drinkers

Increased brain uptake and oxidation of acetate in heavy drinkers Graeme Mason of Yale University discusses how heavy drinking influences metabolism and leads to alternate fuel use in the brain. Highlights:

• Brain acetate consumption is inducible by conditions that can occur with heavy alcohol use.
• Heavy drinking is associated with enhanced ability to import and oxidize acetate.
• Systemic acetate provides a potential metabolic reward for drinking, possibly specific to glia.
• Acetate oxidation provides a mechanism to generate adenosine, whose loss may contribute to withdrawal symptoms.

Spanish and Portuguese versions are also available.

Paul Greengard

If you, or someone you know, has Parkinson’s disease, mental health issues, or other neurological disorders, medication can often help. The bulk of these medications have been established based on the work of neuroscientist Paul Greengard from the Rockefeller University, who worked out just how the brain responds to neurotransmitters — the chemicals that help the brain signal. Most of what most neuroscientists know today about neurotransmission, and specifically the dynamics of slow synaptic transmission, is predicated on the work of Dr. Greengard. The interview features stories about his seminal research discoveries and his competitive streak in potato sack races.

Brain-wide pathway for waste clearance captured by contrast enhanced MRI

Helene Benveniste of Stony Brook University discusses the use of contrast-enhanced MRI to visualize the glymphatic system, a paravascular pathway that facilitates the clearance of waste and solutes from the cerebrospinal fluid and interstitial fluid of the brain. Highlights:

• Glymphatic pathway function can be measured using dynamic contrast-enhanced MRI.
• Benveniste and colleagues used whole brain imaging to identify /confirm key features of the glymphatic pathway in rats.
• Many degenerative brain diseases are associated with the accumulation of proteins that form plaques (ie. Alzheimer’s disease). Clearance of these proteins is mediated by the glymphatic system.
• Contrast-enhanced MRI could potentially be used to evaluate 

Jeffrey Friedman

Dr. Jeffrey Friedman, of Rockefeller University, has been at the center of discovery of the molecular determinants of why we eat what we eat and, more importantly, why we eat so much of what we eat. Over the last three decades, now almost daily in the media, alarm has been sounded about the growing obesity epidemic. Dr. Friedman has spent his research career engaged in the discovery and characterization of leptin, one of the most important hormones regulating appetite and hunger.