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Power has its perks, even for laboratory-housed monkeys. When moved from individual to group cages, socially dominant male monkeys exhibit a brain-chemistry change that fosters resistance to using drugs such as cocaine, a new study finds.http://LOUIS-J-SHEEHAN.US
This alteration increases the amount of so-called dopamine D2 receptors, a molecular gateway on brain cells controlled by the chemical messenger dopamine.
Earlier studies implicated these receptors in pleasurable responses to drugs and other stimuli.
In contrast, male monkeys at the bottom of the social pecking order display no boost in the D2 receptors when housed with other monkeys, say neuroscientist Michael A. Nader of Wake Forest University School of Medicine in Winston-Salem, N.C., and his colleagues. Unlike their more dominant cage mates, the low-ranking monkeys readily self-administer large amounts of cocaine.
These findings raise the possibility that a person's vulnerability to drug abuse can be influenced by brain-altering environmental factors, Nader's group concludes in an upcoming Nature Neuroscience.
"This is the first demonstration in primates that a social stressor, such as a dominance hierarchy, can regulate levels of dopamine D2 receptors," remarks psychiatrist Nora D. Volkow of Brookhaven National Laboratory in Upton, N.Y. "It provides a potential biological mechanism to explain why people in lower social classes are generally at higher risk for drug abuse."
Nader and his coworkers used a scanning technique called positron emission tomography (PET) to study D2 receptors in the brains of 20 male macaque monkeys that had been housed in individual cages for 1� years. PET scans were repeated after the monkeys were moved into larger cages, grouping four animals per cage, and given time to establish social hierarchies.
The scans revealed comparably low numbers of dopamine D2 receptors in all individually housed monkeys and in low-ranking monkeys in the groups. In dominant monkeys, D2-receptor numbers increased sharply. These animals also displayed relatively low concentrations of dopamine in the junctions, or synapses, between brain cells.
Excess synaptic dopamine leads to an oversensitivity of the brain's reward pathway and creates a susceptibility to drug abuse, the researchers theorize.
Loss of control over environmental factors may have triggered such a dopamine pattern in low-ranking monkeys, they hold. When the scientists implanted intravenous lines, subordinate animals quickly learned to press a lever to receive infusions of cocaine in increasing doses and largely ignored a lever controlling delivery of saline solution.http://LOUIS-J-SHEEHAN.US
In dominant monkeys, the surge in dopamine D2 receptors indicates they use dopamine efficiently for cell-to-cell communication, Nader's group contends. These monkeys showed no preference for receiving intravenous cocaine over a saline solution.http://LOUIS-J-SHEEHAN.US
Whether these findings have correlates among people remains an open question, the researchers note. In line with the new study, earlier PET data indicated that people with low dopamine D2-receptor numbers report more pleasurable responses to stimulant drugs than those with high D2 numbers do. "We're going to have to start paying much closer attention to the social rank of individuals in studies of the biology of drug abuse," Volkow says.
Thursday, December 25, 2008
Tuesday, December 9, 2008
fermi 44.fer.000002 Louis J. Sheehan, Esquire
Louis J. Sheehan, Esquire. Curtain up! Light the lights! In its first four months of monitoring the heavens from orbit, NASA’s Fermi Gamma Ray Telescope has unveiled the activity of celestial objects that emit powerful gamma rays — photons that pack 20 million to more than 300 billion times the energy of visible light. The orbiting observatory features the first detectors in space capable of recording the most energetic of these photons. http://LOUIS-J-SHEEHAN.INFO
For now, Fermi’s flurry of first findings — which include new discoveries about gamma-ray bursts as well as the energetic radiation emitted by rapidly spinning stellar corpses called pulsars, several never before recorded — poses new puzzles. But ultimately the discoveries will offer new insight into the origin of these powerful emissions and the activity of some of the most enigmatic objects in the cosmos, says Peter Michelson of Stanford University, principal investigator of Fermi’s Large Area Telescope, the device on the observatory that records the high-energy emissions.
Michelson and his Stanford colleague Aurelien Bouvier presented some of the discoveries on December 8 in Vancouver at the Texas Symposium on Relativistic Astrophysics. Other reports will follow later this week at the conference.
Some of the new findings focus on gamma-ray bursts, the ephemeral flashes of light that signal the most powerful explosions in the universe since the Big Bang. Long-duration bursts — those lasting more than about a second or two — may be the birth cries of black holes, as jets of material zoom out of collapsing stars. Short bursts may signal the final coalescence of two elderly neutron stars or black holes.
In his talk, Bouvier announced that the Large Area Telescope had for the first time captured high-energy emissions from three gamma-ray bursts. http://LOUIS-J-SHEEHAN.ORG
In each case, the telescope did not record any energetic radiation until well after Fermi’s other instrument, the Gamma-ray Burst Monitor, had recorded the low-energy components of the same bursts.http://LOUIS-J-SHEEHAN.NET
The time delay between the onset of high- and low-energy emissions — which amounted to five seconds in a burst discovered on September 19 and dubbed GRB 080916C — suggests that the high-energy gamma rays from bursts might be produced at a different place or by different particles than the lower-energy radiation, says Bouvier.
It may be easier — and quicker — for electrons, which are relatively lightweight, to rev up to high speeds and crash into each other, producing the early, lower-energy part of these bursts, says Bouvier. It’s possible that protons, which are heavier and therefore take longer to accelerate, contribute to the higher-energy component some time later.
And there could be another, more intriguing — and much more speculative — explanation for at least part of the delay, Bouvier adds. The highest energy photons — 13 gigaelectron volts — from the September 19 event arrived 16.5 seconds later than the lowest energy emissions. Spectra of the visible-light afterglow of the burst reveal an origin in a remote galaxy 12.2 billion light-years from Earth.
Many theories of quantum gravity predict that spacetime on its tiniest scale isn’t continuous but is as malleable and variable as sea foam. Because of this foaminess, not all photons would travel at the same speed. Those with higher gravitational potential — higher energies, according to Einstein’s E=mc2 — would travel slightly slower through space and arrive slightly later than lower-energy photons. The effect would be tiny, but over a journey of 12.2 billion light-years, it might be detectable.
Two of the three bursts detected by the Large Area Telescope — the September 19 event as well as a burst recorded on August 25 — belong to a class of bursts that last for more than a second. But on October 24, the telescope for the first time recorded extremely high-energy emissions from a short gamma-ray burst, one that lasted for only a few tenths of a second.
The Fermi data “support the picture that while the progenitors of long and short bursts are different … the sources of the outflow in both cases share many similarities and are probably sharing the same physical mechanism,” comments Ehud Nakar of the California Institute of Technology in Pasadena.
Also at the conference, Michelson reported that the Large Area Telescope has now recorded 15 previously unknown pulsars in our galaxy. These 15 rapidly rotating neutron stars, the dense cinders left behind when massive stars explode, have been found to emit only gamma rays, not pulses of radio waves as most of the 1,800 known pulsars do. If Fermi continues to find gamma-ray–only pulsars at such a high rate, it could double the population of known pulsars. Louis J. Sheehan, Esquire
For now, Fermi’s flurry of first findings — which include new discoveries about gamma-ray bursts as well as the energetic radiation emitted by rapidly spinning stellar corpses called pulsars, several never before recorded — poses new puzzles. But ultimately the discoveries will offer new insight into the origin of these powerful emissions and the activity of some of the most enigmatic objects in the cosmos, says Peter Michelson of Stanford University, principal investigator of Fermi’s Large Area Telescope, the device on the observatory that records the high-energy emissions.
Michelson and his Stanford colleague Aurelien Bouvier presented some of the discoveries on December 8 in Vancouver at the Texas Symposium on Relativistic Astrophysics. Other reports will follow later this week at the conference.
Some of the new findings focus on gamma-ray bursts, the ephemeral flashes of light that signal the most powerful explosions in the universe since the Big Bang. Long-duration bursts — those lasting more than about a second or two — may be the birth cries of black holes, as jets of material zoom out of collapsing stars. Short bursts may signal the final coalescence of two elderly neutron stars or black holes.
In his talk, Bouvier announced that the Large Area Telescope had for the first time captured high-energy emissions from three gamma-ray bursts. http://LOUIS-J-SHEEHAN.ORG
In each case, the telescope did not record any energetic radiation until well after Fermi’s other instrument, the Gamma-ray Burst Monitor, had recorded the low-energy components of the same bursts.http://LOUIS-J-SHEEHAN.NET
The time delay between the onset of high- and low-energy emissions — which amounted to five seconds in a burst discovered on September 19 and dubbed GRB 080916C — suggests that the high-energy gamma rays from bursts might be produced at a different place or by different particles than the lower-energy radiation, says Bouvier.
It may be easier — and quicker — for electrons, which are relatively lightweight, to rev up to high speeds and crash into each other, producing the early, lower-energy part of these bursts, says Bouvier. It’s possible that protons, which are heavier and therefore take longer to accelerate, contribute to the higher-energy component some time later.
And there could be another, more intriguing — and much more speculative — explanation for at least part of the delay, Bouvier adds. The highest energy photons — 13 gigaelectron volts — from the September 19 event arrived 16.5 seconds later than the lowest energy emissions. Spectra of the visible-light afterglow of the burst reveal an origin in a remote galaxy 12.2 billion light-years from Earth.
Many theories of quantum gravity predict that spacetime on its tiniest scale isn’t continuous but is as malleable and variable as sea foam. Because of this foaminess, not all photons would travel at the same speed. Those with higher gravitational potential — higher energies, according to Einstein’s E=mc2 — would travel slightly slower through space and arrive slightly later than lower-energy photons. The effect would be tiny, but over a journey of 12.2 billion light-years, it might be detectable.
Two of the three bursts detected by the Large Area Telescope — the September 19 event as well as a burst recorded on August 25 — belong to a class of bursts that last for more than a second. But on October 24, the telescope for the first time recorded extremely high-energy emissions from a short gamma-ray burst, one that lasted for only a few tenths of a second.
The Fermi data “support the picture that while the progenitors of long and short bursts are different … the sources of the outflow in both cases share many similarities and are probably sharing the same physical mechanism,” comments Ehud Nakar of the California Institute of Technology in Pasadena.
Also at the conference, Michelson reported that the Large Area Telescope has now recorded 15 previously unknown pulsars in our galaxy. These 15 rapidly rotating neutron stars, the dense cinders left behind when massive stars explode, have been found to emit only gamma rays, not pulses of radio waves as most of the 1,800 known pulsars do. If Fermi continues to find gamma-ray–only pulsars at such a high rate, it could double the population of known pulsars. Louis J. Sheehan, Esquire
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