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| Stimulus Control and Behavioral Toxicology |
| Sunday, May 29, 2005 |
| 9:00 AM–9:50 AM |
| Lake Ontario (8th floor) |
| Area: BPH |
| Chair: Miranda Reed (Auburn University) |
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| Effects of Gestational Methylmercury Exposure on Behavior Under External Stimulus Control Following Drug Challenges |
| Domain: Basic Research |
| MIRANDA REED (Auburn University), M. Christopher Newland (Auburn University) |
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| Abstract: Both the in vitro and in vivo literature suggests alterations of catecholamine functioning following gestational methylmercury (MeHg) exposure. The present experiment was designed to examine 1) the interaction between selenium and MeHg 2) the effects of MeHg on bringing lever-pressing behavior under external stimulus control and 3) the disruptive effects of cocaine on this behavior. Female Long-Evans rats were exposed to 0, 0.5, or 5 ppm MeHg via maternal drinking water during gestation as well as a diet either high or low in selenium that continued throughout their lifespan, creating a 2x3 factorial design. Upon reaching adulthood, forty-four female offspring were placed on a MULT FI 120 FIClock 120. The FIClock 120 component was divided into 5 24 second bins. Each of the 5 bins was associated with a different visual stimulus, thus providing the rats with a “clock.” After 42 sessions, the rats were exposed to acute doses of cocaine (1-30mg/kg). Increased sensitivity was found in mercury-exposed rats for both components following cocaine administration. There were only small differences between the FI 120 and FIClock 120 components following cocaine administration for any of the groups, suggesting that either behavior was not controlled by external stimuli or that rats are more sensitive to drug induced response disruptions than are pigeons. Current plans include: 1) modifying the clock to add an auditory component to determine modality specificity and 2) examining drugs that promote dopamine activity via different pharmacological mechanisms, particularly through calcium channels. Research supported by NIH ES 10865. |
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| A Discrimination Procedure for Determining Critical Fusion Frequency in Rats |
| Domain: Basic Research |
| JOHN C. HEATH (Auburn University), M. Christopher Newland (Auburn University) |
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| Abstract: Flicker fusion is the phenomenon of a flickering light appearing as a steady light. The critical fusion frequency (CFF) is the lowest frequency at which this occurs and is an established method of testing the visual system. The development of a reliable, technique to measure the CFF in rats over a long period could enhance research into toxicological assaults on the visual system and allow for longitudinal studies in this area using rats as subjects. A method has been developed for testing flicker fusion using positive reinforcement. Long Evans rats where trained in a discrimination procedure in which they learned to associate a particular lever with either steady or flickering LEDs. Responding on an FR7 schedule, reinforcement was delivered for pressing the left lever in the presence of steady illuminated LEDs, or pressing the right lever in the presence of flickering LEDs. Testing was achieved using a method of constant stimuli and the titration/staircase method. Initial data revealed that even with LEDs that had a peak wavelength of 585nm, and a luminous intensity of 7.3 mcd subjects responded on the correct levers > 80% of the time. Psychophysical functions were achieved giving critical fusion frequencies of 14.86Hz, 9.6Hz and 9.7Hz. |
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