Historically, many scientists have regarded itching as just a less intense version of pain. They have spent decades searching for itch-specific nerve cells to explain how the brain perceives itch differently from pain, but none have been found.

Now researchers at Washington University School of Medicine in St. Louis have discovered that those itch-specific neurons do exist in mice, and their studies suggest that itch and pain signals are transmitted along different pathways in the spinal cord. Reporting in the Aug. 6 issue of Science Express, the advance online publication of the journal Science, the researchers say they can knock out an animal's itch response without affecting its ability to sense and attempt to avoid pain. "This finding has very important therapeutic implications," says Zhou-Feng Chen, Ph.D., the study's principal investigator. "We've shown that particular neurons are critical for the itching sensation but not for pain, which means those cells may contain several itch-specific receptors or signaling molecules that can be explored or identified as targets for future treatment or management of chronic itching."

The new finding follows research by Chen and his team in 2007 that identified the first itch gene — gastrin-releasing peptide receptor (GRPR) — in the spinal cord. They also showed that when mice were exposed to things that make them itchy, those without a GRPR gene scratched less than their normal littermates. Chen's team also found GRPR in a group of spinal-cord cells called lamina 1 neurons that relay both itch and pain sensations to the brain. "But the identification of an itch receptor in spinal-cord neurons didn't mean those neurons were itch-specific because it was possible that they also could have pain-related genes," says Chen, associate professor of anesthesiology, of psychiatry and of developmental biology. "A key question was whether those GRPR neurons also were transmitting pain signals. We approached that question by injecting a toxic substance that binds to GRPR and then exposing mice to both itchy and painful stimuli."

Chen's team injected the spinal cords of mice with a neurotoxin called bombesin-saporin. It bound to GRPR and killed the neurons where the gene was expressed. When these mice then were exposed to things that caused itching, they didn't scratch. With an appropriate dose of the neurotoxin, their scratching could be reduced by more than 80 percent or completely eliminated in some instances. That finding proved that the neurons with GRPR were required for normal itch sensation.

There are two major types of itching that are classified according to the presence or absence of the chemical histamine. Histamine-dependent itching can be caused by bug bites or allergic reactions. It is treated with antihistamine drugs, such as Benadryl®. Most chronic, severe itching, however, is resistant to antihistamine treatment. But in this study, it made no difference whether mice were exposed to histamines or to other itch-inducing substances. Those mice whose GRPR-expressing neurons had been destroyed by the neurotoxin didn't scratch, regardless of what type of itchy agent they encountered. "However, the same mice continued to respond normally to pain," Chen says. "This is a very striking and unexpected result because it suggests there is an itch-specific neuronal pathway in the spinal cord." Further tests showed that other neurologic functions, such as motor control were not affected by the destruction of the GRPR-expressing neurons.

Whereas Chen's earlier work found that pain and itch are regulated through different molecular pathways, this study suggests they also are regulated through different cellular pathways. That, he says, could have important implications for treating itch because the neurons with GRPR may contain more itch-specific genes. "We've shown that these GRPR neurons are important for itching sensation and not for pain, but we really don't know much more about them," Chen says. "We still have a lot of questions, and we are very interested to find more answers."

Researchers say smoking, binge drinking need to be addressed together in adolescents

As teens head back to school, health teachers may want to revise their lesson plans. Temple researchers have found that kids who engage in heavy drinking will more than likely also engage in heavy smoking, and they say educators can help combat the trend by addressing both topics as one health risk. "These are important findings because they emphasize the need for education and intervention programs that target the co-occurrence of these two health risks," said Brian Daly, assistant professor of public health in the College of Health Professions and Social Work.

Daly and colleagues in the department of public health and psychology determined rates of smoking and binge drinking through the collection of anonymous survey data from 2,450 African-American, Hispanic and Caucasian students in grades 9-12 at Philadelphia public high schools. Students' responses were compiled from the 2007 Philadelphia Youth Behavioral Risk Survey (YRBS).

Respondents were asked how many cigarettes they'd had per day over 30 days, and how many days over a 30 day period they'd had 5 or more drinks in a row. Data was broken down by race/ethnicity and gender. Researchers found that while Caucasian adolescents were more likely than African-Americans to engage in either binge drinking or smoking, both groups were equally likely to engage in both at the same time.

"In the past 30 years or so, African Americans have traditionally had the lowest instance of smoking and binge drinking," said Daly, who presented his research at the American Psychological Association's annual meeting this week. "Those low numbers resulted in very few studies which looked at both smoking and binge drinking in a diverse sample; most focused only on instances of these in Caucasian or Hispanic adolescents." Daly says that the equal instances of smoking and binge drinking among both groups highlights the need for a multi-pronged approach to education and intervention. "We can't just focus on educating adolescents about the dangers of just smoking or drinking," he said. "We need to address both as one health risk, and we need to do that for all adolescents, not just one particular group." For example, Daly says that when health education teachers talk about the dangers of smoking, they should also touch on the dangers of binge drinking too, illustrating the connection.

The next phase of Daly's research will break down these rates by grade level to determine exactly when binge drinking and smoking start. "The difference in the mindset of a ninth grader versus a 12th grader is pretty vast," he said. "And if we can determine when kids start this behavior — whether it's the summer after 8th grade, or when they're a sophomore or a senior — it can help us tailor education and treatment plans even more."

Daly directs the YRBS in Philadelphia, a survey that focuses on six major areas, including unintentional injuries and violence, tobacco use, alcohol and other drug use, sexual behaviors, dietary behaviors, and physical inactivity, to determine health risk factors among young people.

Border collies are brightest

Although you wouldn't want one to balance your checkbook, dogs can count. They can also understand more than 150 words and intentionally deceive other dogs and people to get treats, according to psychologist and leading canine researcher Stanley Coren, PhD, of the University of British Columbia. He spoke Saturday on the topic "How Dogs Think" at the American Psychological Association's 117th Annual Convention.

Coren, author of more than a half-dozen popular books on dogs and dog behavior, has reviewed numerous studies to conclude that dogs have the ability to solve complex problems and are more like humans and other higher primates than previously thought. "We all want insight into how our furry companions think, and we want to understand the silly, quirky and apparently irrational behaviors [that] Lassie or Rover demonstrate," Coren said in an interview. "Their stunning flashes of brilliance and creativity are reminders that they may not be Einsteins but are sure closer to humans than we thought."

According to several behavioral measures, Coren says dogs' mental abilities are close to a human child age 2 to 2.5 years. The intelligence of various types of dogs does differ and the dog's breed determines some of these differences, Coren says. "There are three types of dog intelligence: instinctive (what the dog is bred to do), adaptive (how well the dog learns from its environment to solve problems) and working and obedience (the equivalent of 'school learning')."

Data from 208 dog obedience judges from the United States and Canada showed the differences in working and obedience intelligence of dog breeds, according to Coren. "Border collies are number one; poodles are second, followed by German shepherds. Fourth on the list is golden retrievers; fifth, dobermans; sixth, Shetland sheepdogs; and finally, Labrador retrievers," said Coren.

As for language, the average dog can learn 165 words, including signals, and the "super dogs" (those in the top 20 percent of dog intelligence) can learn 250 words, Coren says. "The upper limit of dogs' ability to learn language is partly based on a study of a border collie named Rico who showed knowledge of 200 spoken words and demonstrated 'fast-track learning,' which scientists believed to be found only in humans and language learning apes," Coren said. Dogs can also count up to four or five, said Coren. And they have a basic understanding of arithmetic and will notice errors in simple computations, such as 1+1=1 or 1+1=3.

Four studies he examined looked how dogs solve spatial problems by modeling human or other dogs' behavior using a barrier type problem. Through observation, Coren said, dogs can learn the location of valued items (treats), better routes in the environment (the fastest way to a favorite chair), how to operate mechanisms (such as latches and simple machines) and the meaning of words and symbolic concepts (sometimes by simply listening to people speak and watching their actions). During play, dogs are capable of deliberately trying to deceive other dogs and people in order to get rewards, said Coren. "And they are nearly as successful in deceiving humans as humans are in deceiving dogs."