Sept. 8, 2003
Lead Fallout: Study of lead (Pb) contamination in stream sediment near a clay target shooting range in Fletcher, North Carolina
Mentors: Dr. Mark Brenner and Dr. John Brock
Abstract: Lead poisoning has received recent media attention because of the serious health effects on humans. Common sources of lead are in old paint, pipes, and batteries. Lead (Pb) is a heavy metal that over time settles out into air, water and soils. Identifying the sources of Pb in soils has brought attention to the use of Pb ammunition at outdoor shooting ranges. Previous research theorizes that Pb in soils may be absorbed into the roots of crops and can potentially be prohibited from washing away. The US Fish and Wildlife Service in their Best Management Practices booklet recommends the use of steel or bismuth as alternatives to Pb shot. However, the alternatives to Pb shot are expensive and inferior in performance. The objective of this study was to determine if Pb from Pb shot at the Buncombe County Wildlife and Skeet Club migrates into nearby streambeds. The methods used were based on the previous studies of lead levels in soils. Samples were collected from two upstream locations and four locations downstream of the shooting range. The analytical procedures measured levels of Pb in 10.0 grams of soil by extracting the Pb anion from the soil sample using ethylenediaminetetraacetate (EDTA). An Inductively Coupled Plasma Spectrometer (ICP) was used to measure the concentration of Pb. An ANOVA test was used to compare the means statistically. The statistical analysis showed that there was a significant difference (p < 0.001) between the control sites and the site closest to the shooting range. There was also a significant difference between the control site and second closest sampling site (p < 0.01). These results suggest that Pb migrates off the site of the shooting range. The concentration of the lead ranges from 3.0 ppm Pb to 29.2 ppm Pb, which is less then the EPA’s Pb soil concentration standard (400 ppm).
Sept. 15, 2003
The Effective Pollinators of Japanese Honeysuckle (Lonicera japonica) on Warren Wilson College Campus
Mentor: Dr. Amy Boyd
Abstract: The impacts of invasive species are expected to eventually become severe throughout all ecosystems, as increasing numbers of exotic species become established in new locations. The nonindigenous invasive, Japanese Honeysuckle (Lonicera japonica), is a woody vine with a well-documented capacity for invading and dominating a variety of habitats. Japanese Honeysuckle is completely dependant on pollinators to sexually reproduce. The objective of this study was to determine which pollinators are transferring the most pollen to the stigmas of the Japanese Honeysuckle flowers on Warren Wilson College campus. At 12 sample sites, mesh bags were used to cover the L. japonica flowers 24-48 hours prior to their opening. After the flowers had opened the mesh bags were removed. Once a pollinator visited, the pollinator type was noted and the stigma was preserved on a microscope slide. In the lab, the pollen grains on each stigma were counted. 10 virgin stigmas were collected to serve as a control group, and 20 stigmas were collected for each of the 5 pollinator groups. The pollinator groups were 1) order Hymenoptera, family Apidae, Apis spp. 2) order Hymenoptera, family Apidae, Bombus spp. 3) order Diptera 4) order Lepidoptera 5) order Hymenoptera, family Vespidae. The Kruskal-Wallis Test a nonparametric ANOVA statistical test was performed on the data. The result was a P value that is less than 0.0001 which indicates that the difference between the means of the five pollinator groups and the control group is extremely significant. The Bumble Bees (Bombus spp.) successfully transferred the largest percentage of pollen grains to the Japanese Honeysuckle stigmas and are therefore the most effective pollinators of Japanese Honeysuckle on Warren Wilson College campus. In further research, to improve this study the amount of pollen being removed by the pollinators should be included when comparing the data statistically. Also, the knowledge of the most successful pollinator of Japanese Honeysuckle could lead to a more effective conservation tool for limiting the abundance of Japanese Honeysuckle, by effectively limiting pollination.
Sept. 22, 2003
TumorInhibiting Properties of Poke Weed, Phytolacca americana.
Mentor: Dr. Dean C. Kahl
Abstract The tumors produced by Agrobacterium tumefaciens can be used as a crude model for human tumors (Galsky et al.). Substances that inhibit the growth of Agrobacterium tumefaciens might also inhibit the growth of human tumors and might merit further studies. In this study 15 different pokeweed root extracts were used to determine whether ethanol extracts of pokeweed have tumor inhibiting properties. The extracts were prepared by grinding the dried roots and mixing 20g of root powder with 100mL of 95%ethanol. After sitting for 6 weeks this extract, or tincture was applied to tumors initiated by Agrobacterium tumefaciens. The other treatments included a positive control of DMSO and three negative controls consisting of water, alcohol and lack of treatment. The data was analyzed by a conservative Mann Whitney non-parametric test because the data was not normally distributed even when transformed. The results showed potatoes treated with the ethanol and the ethanol extract of pokeweed roots had statistically significantly less tumors than the negative water control, which suggests that ethanol killed the bacterium before potatoes were fully infected by tumors. DMSO failed as a positive control because the number of tumors were not significantly reduced. Ethanol failed as a negative control because it appears to reduce the number of tumors. Thus, future studies need to investigate whether it was the ethanol or the pokeweed extract that eradicated the tumors. More sophisticated procedures using animals should follow this study to provide more information about the tumor inhibiting properties of poke. Also a water extract should be used for further research on Crown Gall Tumor inhibition by pokeweed.
September 29, 2003
Computer Analysis of Photochemical Smog
Mentor: Dr. Dean C. Kahl
Abstract: Photochemical smog forms when volatile organic compounds (VOC) and nitrogen oxides (NO and NO2) react in the presence of light to form ozone (O3). Theoretical models of photochemical smog formation can explain the formation of smog, and smog chamber data is used to test the validity of these models. Photochemical smog models are used to predict the effects of lowering concentrations of VOCs and NO, a situation that occurs with catalytic converters in automobiles. The objectives of this research were to create a simple Mathcad program to model smog formation for Introduction to Environmental Studies and General Chemistry II, compare the results to smog chamber data, and simulate the effect of a catalytic converter. Mathcad is a powerful calculation software that solves just about any math problem. The seven-reaction mechanism developed by Friedlander and Seinfeld (1969) was implemented using Mathcad and numerical integration. This mechanism was chosen because it is very simple. The result was a graph of pollutant concentration versus time. The graphs were similar to smog chamber data. The mechanism works for HC, NO, and NO2 but could not predict O3 concentration. The program was used to simulate the effect of a catalytic converter in an automobile. When the concentration of HC was lowered, the concentration of NO2 remained low. When the concentration of NO was lowered, the concentration of NO2 remained low. The program has potential to be used in the classroom, but the failure to predict O3 concentration will limit the use of this model. The major weakness of the mechanism is that it has many approximations and in particular it ignores the effect of the OH radical.
September 29, 2003
Demographics of the Common Snapping Turtle (Chelydra serpentina serpentina) in the Warren Wilson College Pig Pond
Mentor: Dr. Lou Weber
Abstract: Turtles of all species are facing a global conservation crisis. Common snapping turtle (Chelydra serpentina) populations are facing increased pressures. These pressures include unknown causes of adult mortality, habitat degradation and commercial over-harvesting. The global demand for turtles in the Asian turtle markets has led to unsustainable harvesting of many turtle species, including the common snapping turtle. The objectives of my research were to determine the demographics (age, gender, and number) of the common snapping turtle in the Warren Wilson College Pig Pond and to use those demographics to look at conservation issues and management implications. To do this I conducted a mark-recapture study in the spring of 2003. I determined the carapace length, gender, and minimum age of each turtle caught. The demographic study resulted in a population estimate of 27 common snapping turtles. The average age of the common snapping turtles was 14 years with seven out of the nine females being above the reproductive age of 12. The average size of the carapace was 25 cm by 24 cm and the sex ratio was ten males to nine females. The common snapping turtle population in the Warren Wilson College Pig Pond has little juvenile recruitment. To increase this I suggest that along with the protection of adults, there needs to be management strategies that will increase juvenile recruitment. These would include creating turtle corridors that are free from agricultural development and to create appropriate nesting sites within close proximity to the Pig Pond.
October 6, 2003
Effective production of Biodiesel
Mentor: Dr. Dean Kahl
Abstract: Biodiesel is produced by the reaction of vegetable oils, methanol and a base such as sodium hydroxide (NaOH). The biodiesel fuel is a mixture of methyl esters that can function in diesel engines like diesel fuel. As diesel fuel is a non-renewable fuel biodiesel could help our current fuel situation. My objective was to determine the optimum conditions for producing biodiesel fuel, finding the optimum concentration of alcohol and catalyst. To make the biodiesel, methanol and sodium hydroxide in varying amounts were added to oil in 350 mL Mason jars. The viscosity of these solutions was then measured to determine the quality of the fuel. Using a 2 way ANOVA I was unable to prove any significant difference (p=0.27) and as such no interaction term. However an interaction must exist because one of the treatment groups I, the low methanol, high base group failed; while the other low methanol, and other high sodium hydroxide groups succeeded. All my treatments groups had a lower viscosity than the standard of 7.5 Cst at 20° C. In conclusion, Biodiesel can be made to good quality if an approximate 6/1 mole ratio of alcohol to oil, and an approximate 0.5% NaOH are used.
October 6, 2003
The Effects of Poultry Husbandry on Carotenoid levels in Egg Yolks
Mentor: Dr. Victoria P. Collins
Abstract: Carotenoids are yellow and orange pigments found in all photosynthetic plants and some animal tissues including eggs. Animal studies have shown an inverse correlation between common degenerative diseases and serum carotenoid levels in animals. The objectives of this study were 1) to develop a method using the HPLC to determine the carotenoid concentrations within eggs, 2) compare carotenoid levels of pastured vs. conventional eggs and 3) to see if their was a correlation between yolk color measured with the Roche color fan, and carotenoid concentrations. The method developed used ether as the solvent to extract the carotenoids from the yolk. The carotenoids were separated and quantified by reverse phase HPLC with a mobile phase of 5% tetrahydrafuran and 95% acetonitrile. Carotenoids were detected by absorbance at 450 nm. There were two treatments for this study 1) conventional eggs- produced by chickens without access to pasture and, 2) pastured eggs- produced by chickens with access to pasture. With in each treatment there were six replicates. Beta-carotene, cryptoxanthin, zeaxanthin and lutein were the four carotenoids observed in the study. The method was capable of identifying and quantifying all four compounds; however beta-carotene and cryptoxanthin were found in trace amounts in a few of the brands. Lutein and zeaxanthin concentrations of the two treatments differed with a p-value < 0.02. The conventional eggs had a combined lutein and zeaxanthin concentration of 1.75 ppm and the pastured eggs had a combined lutein and zeaxanthin concentration of 4.82 ppm. There was no correlation between yolk color and lutein concentrations within the yolks. The average pastured brand contained 1 mg of lutein per egg. In conclusion justification for the premium paid for pastured eggs should not primarly be based on health benefits associated with the eggs, but the humane methods in which they are raised.
Marta Gwynne Eckert-Mills
October 13, 2003
Carapace color change in aquacultured blue crabs (Callinectes sapidus) and effect of color on predation
Mentor: Dr. Amy Boyd
Abstract: As part of a blue crab stock enhancement project in the upper Chesapeake Bay, the ability of juvenile blue crabs, Callinectes sapidus, to change carapace color to match substrate color was studied. Carapace color is a characteristic that potentially affects the survival of hatchery-raised individuals once released into the wild. Color differences were noticed between hatchery-raised and wild blue crabs, as were differences in survivorship. My objectives were to determine the ability of hatchery-raised juvenile blue crabs to change carapace color in response to habitat color and to examine the potential link between color difference and survivorship. Hatchery-raised juvenile crabs were exposed to differing substrates (white, tank liner, or sand) and were monitored for change in carapace color over a one to two week period. Color hue, saturation, and brightness were affected by substrate color after one day of exposure to treatments. Crabs placed on white substrate were significantly bluer (as opposed to greener) and were higher in color saturation and brightness than those placed on sand substrate. The overall spottiness (variation in color) of carapace color did not appear to be affected by substrate color. No consistent significant difference was found between the color of crabs on the tank liner and those on either the white or sand treatments. This study shows that juvenile blue crabs do have the ability to alter their carapace color to match substrate color. The mechanism of this color change was not determined, although crabs did not need to molt in order to alter carapace color, nor was gender a factor in color-changing abilities. I also determined the effect of carapace color on predation rates. Crabs were tethered in a tributary of the Rhode River and exposed to juvenile striped bass predators in lab trials. Crabs that had been on sand substrate had slightly, but not significantly, lower predation rates than crabs that had been on white substrate. My results indicate that carapace color change of juvenile blue crabs is easily induced by environmental cues and hatchery-raised individuals can be conditioned to look more like wild crabs. Further study may focus on the impact of color on overall survivorship of blue crabs in the wild and the biological effects of this morphological difference.
November 10, 2003
Free Radical Scavenging Capacity of Grapeseed Products:
Mentor: Dr. Victoria P. Collins
Abstract: Free radicals are atoms or molecules with an unpaired electron; though they are electrically neutral, the unpaired electron causes them to act as if they were electron deficient. Free radicals become stable via oxidation; they strip electrons from other compounds. In body tissues, membrane fatty acids are the main source of these electrons. Products made from grapeseeds have antioxidant properties; grapeseed antioxidants scavenge free radicals from the body. In this study the %Radical Scavenging Capacity (RSC) of three grape seed product groups, oils, tablets and extracts, was studied spectrophotometerically using the stable free radical DPPH· (Diphenylpircylhydrazyl radical). Samples (equal weight concentration with 100uM vitamin E) and DPPH· (50uM) were dissolved in MeOH and the removal of DPPH· radical was monitored by the change in absorbance at 517nm. 100uM vitamin E was the positive control and %RSC was calculated as the % change in absorbance after 150sec. The RSC values were as follows: oils, 59.53%RSC, tablets, 41.34%RSC, extracts, 19.41% RSC. The product groups differed in RSC (P=0.0439). Within product groups, there was very little variation of RSC between brands (Oils, P=0.586), (Extracts, P=0.100), (Tablets, P=0.051). On an equal weight basis, oils were 78% as effective as vitamin E, tablets were 54%, and extracts were 25% as effective. This study showed grapeseed products to be extremely powerful antioxidants, and indicated a possible use for the primary waste product of grape farming.
November 17, 2003
Non-Native, Invasive Plant Species Monitoring at Warren Wilson College
Mentor: Dr. Lou Weber
Abstract: Non-native plant species have been introduced to natural areas by human activity both accidentally and deliberately. Non-native species growing in an ecosystem which they did not evolve in, may become invasive. Biological invasions, as a cause of species extinction is second only to habitat destruction. Invasions of non-native plant species threaten native species by causing changes in species composition through competition, suppression, and displacement. Theses non-native species not only compete with native species, but may alter atmospheric composition, local hydrology and climate by altering ecosystem conditions and changing local resource availability. Jones Mountain at Warren Wilson College is the site for biological invasions of at least seven non-native plant species. The Natural Resources Crew (NRC) has been using prescribed burning, herbicides, and mechanical control methods for seven years to control the growth of non-native species on Jones Mountain. There has been no monitoring plan or record keeping system for the Natural Resources Crew’s management activities on Jones Mountain. My objectives were to create a monitoring system for non-native populations in managed areas on Jones Mountain, to create a record-keeping system for management activities, and to implement these systems into the Natural Resources Crew framework through teaching. I established six permanent plots in areas where NRC is actively managing to control non-native species. I estimated the population size and density of thirteen non-native species within each plot by sampling. The sample plots, called sub plots, were regularly distributed on a on a 20-meter by 20-meter grid. I counted the total number of stems of each species in every sub-plot. I have created a record keeping system for prescribed burns, herbicide use, and mechanical controls, and the crew has begun to use the system. I have trained members of NRC to identify the non-native species, establish and monitor permanent plots and sub plots, and fill out the treatment forms. The sampling will be done by crew members annually, and the number of permanent plots will increase as NRC continues to manage the non-native populations in new areas. As data are collected by the crew, a body of information will be created which will be statistically analyzed to determine changes in non-native populations, the causal agents, and what effect our management practices are having on existing conditions. This information is essential for making management decisions.
November 24, 2003
Chemotaxis in the True Slime Mold Physarum polycephalum
Mentor: Dr. Jeffrey Holmes
Abstract: Physarum polycephalum is a plasmodial slime mold of the class Myxomycetes that exhibits chemotactic responses to a variety of chemical compounds. This study sought to compare the attractiveness of substances when these substances were competing to direct the motion of the plasmodium. Chemotaxis was assayed by the methods developed by Kincaid and Mansour (1978b). The attractiveness of each chemical tested was compared to a deionized water control using an unpaired two-tailed t-test. The Welch correction was used to compensate for unequal standard deviations. D-glucose, at concentrations of 0.001M, 0.010M, 1.0M and 5.00M, showed no significant difference in the direction of movement than a deionized water control. No significant difference was also shown for 1.0M L-glycine or 0.05M L-asparagine as attractants. There was a significant difference between movement towards control and test strips on assays using D-galactose, at a concentration of 0.010M, however the migration was away from the galactose rather than towards it. Previously published literature suggested that 0.010M D-galactose would act as an attractant. I conclude that under the conditions used in this study, the tested P. polycephalum culture exhibited no chemotaxis. This has not been previously reported. A hypothesis is proposed that the culture used in this study has undergone a mutation in some component of the chemotactic pathway.
December 1, 2003
The Effect of a Pasture Environment on Piglet Weight Gain and Internal Parasite Burden.
Mentor: Dr. Jeff Holmes
Abstract: The movement of swine operations from traditional systems to more modern and intensive production has led to a decrease in the number of worm species and burdens in domestic pigs. The effect of moving the domestic pig back to pasture rearing was examined in this study through measures of the productivity factors weight gain and internal parasite burden. For July through August of 2003, ten sows were divided into two farrowing groups: outdoor and indoor. The piglets were born and reared to weaning in the established environments. Stool samples were attempted to be collected from each piglet born into the study, numbering 52 indoor and 48 outdoor, at 10 days of age and at weaning. The average numbers of eggs counted per sample per litter per treatment, with a sample total of 29 indoor and 36 outdoor, were analyzed using the Mann-Whitney non-parametric test resulting in a p-value of 0.02, suggesting that there were significantly more eggs observed in the outdoor reared piglets. The piglets were weighed at birth, 10 days of age, and at weaning. The mean average daily gain of the treatments were calculated and analyzed using One-Way ANOVA, resulting in a p-value of 0.115, suggesting that the gain of the outdoor and indoor reared piglets was comparable. A correlation of the average number of eggs counted per litter and that litter’s calculated average daily gain suggested that as the number of eggs counted increased, the average daily gain decreased, with a correlation factor of –0.70. While the gain of the treatments was comparable, the study demonstrated that the increased parasite egg counts possibly could have a notable effect on gain.
Feb. 2, 2004
Road Mortality on the Blue Ridge Parkway
Mentor: Dr. Lou Weber
Abstract: The Blue Ridge Parkway is a 469-mile recreational motor road that connects the Shenandoah and Great Smoky Mountains National Parks. It is the most visited of all the National Parks and is unique because of its constant speed, diverse habitats, and varying road conditions. This observational study was conducted on the Blue Ridge Parkway with the help of the National Park Service to document road mortality and the factors influencing road mortality, such as weather condition, temperature, lunar phase, land use, mile point, road type and location, and scavenging frequency. This eight-month study began in April 2003 and ended in November of 2003. Three surveyors conducted a 20-mile survey once a week. Each surveyor was assigned a 100-mile survey area, and each week a 20-mile survey section was randomly selected within the 100-mile survey area. A one-mile walking survey was randomly selected within the 20-mile survey section. Species located while driving to and from a 20-mile survey section were also recorded. Most species found on the Parkway were typical woodland wild life species, and most mortality occurred during the months of June and September. Species mortality seemed to be affected by temperature, animal behavior, and traffic density. Most species were found in the middle or outer ¼ of the road, and on roads types that were curving and straight. Mortalities occurred more often after nights of steady rain, clouds, and clear skies. The first and last quarter of the lunar cycle documented higher mortality numbers.
This study resulted in a base knowledge of what species were being killed on the Parkway, where they were being killed, and gave some indication of why they were being hit. Further research that focuses on specific factors affecting road mortality is needed to conclude if they are significantly affecting road mortality on the Blue Ridge Parkway.
Feb. 9, 2004
Agricultural Effects on the Water Quality of Bull and Shope Creek, North Carolina
Mentor: Dr. Mark Brenner
Abstract: Agriculture can negatively impact water quality, especially when surface water from farms enters nearby waterways. This runoff can have an effect on total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD) and fecal coliform levels. These four indicators were surveyed at five different sampling sites over a period of three months. Repeated measures ANOVA (α = 0.05) was used to determine the effects of agriculture on Bull Creek. The p-values of all of the indicators were above 0.05, suggesting agriculture has no significant effect on these measures of water quality at this site. However, samples taken after storm events may better account for the effects of runoff. Preliminary testing indicates sampling for fecal coliform should be limited to warmer months.
Matthew K. Moerschbaecher
Feb. 16, 2004
A Survey of Road-Kill Along the Blue Ridge Parkway
Mentor: Dr. Lou Weber
Abstract: The Blue Ridge Parkway is a
administered by the National Park Service (NPS), which stretches 469
miles from Shenandoah National Park in Virginia to the Great Smokey
Mountains National Park in North Carolina. The NPS has the
primary responsibility of conserving all of the park’s
resources for the enjoyment of visitors. One of these resources
is wildlife. This study is an attempt to better understand
which species of wildlife are being directly affected by vehicular
traffic along a specific road segment as well as what might be the
cause of the high road-kill rate. Driving surveys were
conducted twice a day for twenty days between mid-October and
mid-November along the Parkway between the Folk Art Center (m.m.
382.2) and the intersection of N.C. Hwy 191 (m.m. 393.6). Each
survey consisted of locating and identifying those individuals, which
had died as a result of being hit by a motor vehicle. The first
survey occurred between 4 p.m. and 5 p.m. and the second survey took
place between 8 p.m. and 9p.m. There was a significantly higher
frequency of road-kill from 5 p.m. – 8 p.m. than expected by
chance (Chi-square P < 0.025). The Eastern Gray squirrel (Sciurus
carolinensis) was the species found most often followed by the
opossum (Didelphis marsupialis). The results suggest that
road-kill is occurring at an unusually high rate between the hours of
5 p.m. and 8 p.m. The causes for this increase in
road-kills may be due to commuter traffic from the nearby city of
Asheville. Traffic counts at the four intersections in the
study section are higher than at any other point along the
A number of different mitigation techniques are suggested to try and
reduce the amount of road-kill in an effort to better conserve
wildlife as a resource.
March 1, 2004
Phthalate Analysis in Household Air Fresheners
Mentor: Dr. John Brock
Abstract: Used in numerous products ranging from personal care products to plastic products, phthalates are ubiquitous in the environment and in humans. Research suggests that exposure to phthalates can cause reproductive and respiratory health effects. The sources of excessive phthalate exposure to humans is still fairly unknown, and air fresheners have been a proposed source of concern due to phthalate use in products that are scented. The objective of this study was to identify and quantify any phthalates found in three different brands of “plug-in” air fresheners using GC/MS. Selective ion monitoring and the use of an internal standard increased the sensitivity of the analysis. Dimethyl phthalate (DMP) was found in all of the products, with the most significant concentration found in Glade Vanilla Breeze at 11.1 ppm. Diethyl phthalate (DEP) was found in two of the products, Renuzit After the Rain and Airwick Plumeria and Wild Rose at concentrations of 6.0 and 18.2 ppm respectively. Diethylhexyl phthalate (DEHP) was found only in the Renuzit product at a concentration of 17.0 ppm. Dioctyl phthalate (DOP) was only found in the Airwick product at a concentration of 2.4 ppm. Not only did the concentration of particular phthalates vary among products but also between different lot numbers of the same product, with the exception of Glade. The variation between lot numbers may mean that the product manufacturers tend to use compounds that are most readily available as opposed to a consistent recipe. This research displays another route of exposure of phthalates to humans through indoor air.
Abstract: Norepinephrine (NE) is found in many regions of the brain including the medial prefrontal cortex (mPFC). Dysfunction of the mPFC results in schizophrenia, depression and bipolar disorder. Furthermore, one potential function of NE is to facilitate an anxiety-like behavioral responses to stress. The purpose of this project was to ask how this function might contribute to the behavioral effects of antidepressants that block NE re-uptake and alleviate the symptoms of depression, including anxiety. To explore this, a change in behavior in the novel open field after chronic, or long term, treatment with the antidepressant drug desipramine (DMI), a NE re-uptake blocker, was examined. A second question was asked to determine if any such change in behavior after DMI treatment could be attributed to a change in NE transmission specifically in the mPFC. Sixty-two male Sprague-Dawley rats were subjected to two drug treatments; the first was a chronic, or long term, drug treatment with either a control or the antidepressant DMI, administered through an osmotic minipump inserted under the skin. After three weeks, either a control, an a1 receptor blocker benoxathian, or a cocktail of b1 and b2 receptor blocker were administered by acute bilateral microinjection into the mPFC. Following microinjection into the mPFC, the rats were placed in a novel open field for 5 minutes, and their behavior video taped for off-line analysis. Measures included center line crossings, total line crossings, and center time. Then, the ratio of center to total line crossings (CTR) was calculated as a measure of center exploration independent of locomotion. There was a significant chronic treatment interaction and acute treatment interaction for center time by ANOVA (F(2,56) = 4.398, p < 0.05). However, the post hoc analysis Newman-Keuls revealed that no individual comparisons were significant. No significant changes in total line crossings could be detected with ANOVA. The antidepressant, DMI, increased CTR (F(2,56) = 6.325, p < 0.05). This individual comparison was found to be significant with the post-hoc test Newman-Keuls. The a1 receptor antagonist did not change CTR in control treated animals, but the a1 receptor antagonist did decrease CTR in DMI treated animals back to baseline control levels. This interaction between the long term pretreatment and the acute pretreatment was found to be significant by ANOVA (F(2,56) = 7.039, p< 0.05). Furthermore, Newman-Keuls confirms that the CTR in chronically treated DMI rats was higher than the CTR in rats chronically treated with a control. Newman-Keuls, also, confirmed that animals receiving DMI treatment and the a1 receptor blocker had a lower CTR than animals receiving just the DMI treatment. From these data, we can conclude that DMI decreased what we believe is an acute stress-induced anxiety in the rats, and this effect can be attributed at least in part to a change in NE binding on the µ1 receptors in the medial prefrontal cortex.
NOTE: All animal procedures were reviewed and approved by the Institutional Animal Care and Use Committee of the University of Texas Health Science Center at San Antonio, and were conducted in accordance with National Institutes of Health guidelines.