Galanin, studied by Emory neuroscientist David Weinshenker’s lab, is not as flashy as other neuropeptides. While it is accumulating an intriguing track record, galanin appears to play subtly different roles depending on where it is expressed. It is tempting to call galanin the “keep calm and carry on” hormone, but the research on galanin is so complex it’s difficult to pin down.
Graduate student Rachel Tillage and colleagues have a paper this week in Journal of Neuroscience detailing how galanin’s production by one group of neurons in the brainstem confers stress resilience in mice.
The new paper shows that exercise increases galanin in the locus coeruleus, a region in the brainstem that produces norepinephrine (important for attention, alertness, anxiety and muscle tone). Galanin can provide protection against the anxiety-inducing effects of artificial but very specific locus coeruleus activation by optogenetics.
Neuroscientist and geneticist David Weinshenker makes a case that the locus coeruleus (LC), a small region of the brainstem and part of the pons, is among the earliest regions to show signs of degeneration in both Alzheimer’s and Parkinson’s disease. You can check it out in Trends in Neurosciences.
The LC is the main source of the neurotransmitter norepinephrine in the brain, and gets its name (Latin for “blue spot”) from the pigment neuromelanin, which is formed as a byproduct of the synthesis of norepinephrine and its related neurotransmitter dopamine. The LC has connections all over the brain, and is thought to be involved in arousal and attention, stress responses, learning and memory, and the sleep-wake cycle.
Cells in the locus coeruleus are lost in mild cognitive impairment and Alzheimer’s. From Kelly et al Acta Neuropath. Comm. (2017) via Creative Commons
The protein tau is one of the toxic proteins tied to Alzheimer’s, and it forms intracellular tangles. Pathologists have observed that precursors to tau tangles can be found in the LC in apparently healthy people before anywhere else in the brain, sometimes during the first few decades of life, Weinshenker writes. A similar bad actor in Parkinson’s, alpha-synuclein, can also be detected in the LC before other parts of the brain that are well known for damage in Parkinson’s, such as the dopamine neurons in the substantia nigra.
“The LC is the earliest site to show tau pathology in AD and one of the earliest (but not the earliest) site to show alpha-synuclein pathology in PD,” Weinshenker tells Lab Land. “The degeneration of the cells in both these diseases is more gradual. It probably starts in the terminals/fibers and eventually the cell bodies die.” Read more
The locus coeruleus is a part of the brain that has been getting a lot of attention recently from Emory neuroscienceÂ researchers.
The locus coeruleus is the biggest source of the neurotransmitter norepinephrine in the brain. Located deep in the brainstem, it has connections all over the brain, and is thought to be involved in arousal and attention, stress, memory, the sleep-wake cycle and balance.
Researchers interested in neurodegenerative disease want to look at the locus coeruleus because it may be one of the first structures to degenerate in diseases such as Alzheimerâ€™s and Parkinsonâ€™s. In particular, the influential studies of German neuro-anatomist Heiko Braak highlight the locus coeruleus as a key â€œcanary in the coal mineâ€ indicator of neurodegeneration.
Thatâ€™s why neurologist Dan Huddleston, working with biomedical imaging specialists Xiangchuan Chen and Xiaoping Hu and colleagues at Emory, hasÂ been developing a method for estimating the volume of the locus coeruleus by magnetic resonance imaging (MRI). Their procedure uses MRI tuned in such a way to detect the pigment neuromelanin (see panel), whichÂ accumulate in both theÂ locus coeruleus and in the substantia nigra. Read more