Detecting circumventricular organ (CVO) toxicity

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POSTER ABSTRACTS--METHODS IN BEHAVIORAL TOXICOLOGY AND TERATOLOGY

course of the interval. Responding after administration of damphetamine (0.3-5.6 mg/kg), pentobarbital (3.0-17.8 mg/kg), or MK801 (0.03-0.32 mg/kg) was predominantly on the S key. Fentanyl was generalized to the morphine stimulus at doses of 0.032 mg/kg or greater with responding predominantly on the M key. Morphine, d-amphetamine, pentobarbital, and fentanyl produced decreases in response rate at the higher doses. MK801 produced response rate increases in three of the four subjects tested. The use of a fixed-interval schedule of reinforcement in a drug discrimination paradigm appears to provide a useful alternative for the study of the stimulus properties of drugs. Supported by NIDA grants DA-02251 and DA-04278. A NEW METHOD FOR MEASURING THE AIR-RIGHTING REFLEX IN DEVELOPING RATS. D. R. Minck, K. D. Acuff and C. V. Vorbees. Institute for Developmental Research, Children's Hospital Research Foundation and University of Cincinnati, Cincinnati, OH. The ability of an animal to right itself during a free fall from a supine starting position has been used for many years as a measure of the dynamic righting reflex. The apparent specificity of the response and the ease with which it can be performed have made it a widely used test to investigate the maturation of the nervous system. In most cases, the reflex is tested by suspending an animal in a "back down" position, either by hand or on a "cling bar", and then releasing it so that it has a free fall of a set distance in which it will right itself into a "prone" position in order to land on its feet. The ability of the animal to land on its feet is then assessed as successful, partially successful, or not successful, based on the judgment of the observer. A new technique for assessing the righting reflex has been devised and is reported here. In this technique a stop-action photographic system is used to stroboscopically record the righting process in rats at various stages of the response as they fall and land. This eliminates the judgment of previous methods and allows for more definitive ratings. Data comparing the observer and stroboscopic methods for measuring the righting reflex in control animals will be presented. PSYCHOPHARMACOLOGICAL STUDIES OF GESTATIONAL COCAINE EXPOSURE: EVIDENCE FOR ENHANCED D2 DOPAMINE RECEPTOR FUNCTION. C. A. Moody, N. A. Frambes and L. P. Spear. Department of Psychology and Center for Developmental Psychobiology, SUNY, Binghamton, NY. In an effort to assess the possible teratogenic effects of prenatal cocaine exposure, behaviors of weanling rats which have been previously exposed to cocaine in utero were observed after pharmacological challenge with the D2 agonist quinpirole. Sprague-Dawley rat dams were subcutaneously (SC) injected daily with cocaine hydrochloride from gestational days 8-20 (E8-20) at doses of 0 (saline control), or 40 mg/kg 3 cc. Control animals in these experiments consisted of dams allowed ad lib access to lab chow. On postnatal day 1 (P1), all litters were fostered to surrogate dams until time of testing. Weanling rats were SC injected with 0, 0.04, 0.08, 0.5 or 1.0 mg/kg 3 cc of quinpirole with only one pup per litter being placed into each drug group. Immediately following injection, pups were individually placed in a testing apparatus containing a food pellet and a wood block. At 30 and 60 min postinjection behaviors were recorded for 5 min every 20 sec via time sampling. Weanling rats prenatally exposed to cocaine exhibited a shift to the left in the quinpirole dose response curve for supported rear/wall climb and forward locomo-

tion. Cocaine-exposed offspring exhibited significant increases in these behaviors at 0.08 mg/kg quinpirole, whereas control offspring showed increases in these behaviors only at a dose of 0.5 mg/kg and greater. Cocaine-exposed offspring also exhibited more rearing, sniffing and chewing of pellet than control offspring. These data suggest that prenatal cocaine exposure increases sensitivity to the D2 agonist quinpirole. These psychopharmacological data are consistent with autoradiographic data collected in conjunction with Ron Hammer (U. Hawaii) demonstrating increased D2 binding in numerous brain regions of weanling animals exposed gestationally to cocaine. Thus, psychopharmacological techniques may prove useful in providing initial assessments of potential alterations in neural function induced by developmental toxicants; these findings can be confirrned and extended using neurobiological techniques. AUTOMATED DOSING AND WEIGHING SYSTEM WITH AUDIT-TRAILED DATA ACQUISITION AND MANAGEMENT. R. M. Parker, J. A. Crowell, P. A. Gosnell, T. J. Bucci. Pathology Associates Inc., NCTR, Jefferson, AR; J. Meehan. UNISYS, DRIMS, NCTR; J. C. Dacre. U.S. Army Biomedical Research and Development Laboratory, Fort Detrick, MD. The Inlife Dosing System is used to dose animals on studies at the National Center for Toxicological Research (NCTR). This program was developed to meet stringent chemical agent tracking requirements for DoD Studies. The program enforces a studyspecific protocol to set the experimental parameters and drive the menus for the study. To start the program, the technician logs on the VAX 780 Computer and identifies the dosing team, the study, the room and equipment that will be used and then proceeds to calibrate the equipment. The technician then adds the container with the chemical agent and primes the Micrometic Systems Automatic Pipette. When ready to begin dosing, the technician barcodes the animal ID and cage ID using an Intermec 9510 Barcode Reader, and weighs the animal on a Mettler PE 11 balance. The weight value is transmitted directly into NCTR Inlife Dosing program. The system uses the weight, along with dosing parameters taken from study specific files, to calculate the correct dose for the animals. The calculated volume information is sent to a Micromedic Pipette which draws up the required dose. The technician selects the proper site of administration and presses a foot pedal to dispense the dose. A time-stamped record of the dosing or any aberration to the dosing protocol (spills, regurgitation, blocked needles, etc.) is stored permanently as part of a comprehensive audit trail on the NCTR database along with other data relating to the study. The program will not allow an animal that has already received a dose to be accidentally redosed and the system prompts for animals that should have been dosed but were not and requires a technician comment for each case that remains not dosed. This program reduces errors by minimizing operator data entry, relying instead upon parameters read from files and instruments. Automatic calculation and highly accurate dispensing of the dose further ensures reliability. Data integrity has been validated and is maintained through conformance to FDA Good Laboratory Practice (GLP) standards for Automated Data Processing. This system is a cost-effective tool for dispensing and tracking the chemical agent and minimizes the time required for hand entry recordkeeping (especially in a GLP environment). DETECTING CIRCUMVENTRICULAR ORGAN (CVO) TOXICITY. A. C. Scallet, J. W. Bryan, IV, R. Rountree and A. Andrews. National Center for Toxicological Research, Jefferson, AR.

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The CVOs (arcuate nucleus, area postrema, and others) are preferentially exposed to blood-borne neurotoxicants since they lack the protection of a blood-brain barrier. Various chemicals produce necrosis of CVO cells, but monosodium glutamate (MSG) has most often been used experimentally. To compare methods to detect altered CVO function, male rats (n= 17-23) received subcutaneous MSG on postnatal days 2, 4, 6, 8, and 10 (4 mg/g/day, group SC4) or orally by gavage (4 mg/g, group PO4 or 2 mg/g, group PO2) according to the same schedule. Controls (Cs) received SC or PO saline. PO2 and PO4 rats showed a dose-related decrease in body weight through 3 months of age. SC4 rats weighed the least until 13-14 weeks, when their weight-gain accelerated markedly. At 8 months, the nose-to-anus length of PO4s was less than Cs (p<0.01), and SC4s were shorter than either PO4s or Cs (p<0.01). On a hotplate analgesia test, SC4s and, to a lesser extent, PO4s had longer baseline latencies and greater response to morphine than Cs. The results signify that oral dosing of neonates with MSG may have prolonged effects on their growth and development. Immunohistochemical evaluation of the CVOs of these animals is underway.

the presence of the drug vehicle (saline) in order to obtain a food reinforcer. A multiple schedule of reinforcement was used to control the conditions under which the subjects could earn the reinforcer. In one component of the multiple schedule the first response on the appropriate lever (pentobarbital or saline), after 180 seconds had elapsed since delivery of the last reinforcer, resulted in the delivery of the next reinforcer, i.e., a fixed interval 180-second schedule of reinforcement. In the other component the subjects were trained to emit 20 responses on the appropriate lever in order to obtain the food reinforcer, i.e., a fixed ratio 20 schedule of reinforcement. After the discrimination behavior of the subjects had become stable, a dose-response curve was determined for pentobarbital. The results were that the subjects emitted a greater proportion of drug-appropriate responses at low doses during the FI than during the FR schedule, but that the FR schedule produced a much steeper generalization gradient. This difference in slope produced a crossing of the curves at higher doses. Thus, the schedule of reinforcement determined the degree of behavioral control exerted by the presence or absence of the pentobarbital stimulus.

A DATA ACQUISITION SYSTEM FOR OPERANT PROCEDURES. J. B. Smith. Worcester Foundation for Experimental Biology, Shrewsbury, MA.

BEHAVIORAL AND NEUROCHEMICAL CONSEQUENCES OF PERINATAL EXPOSURE TO TYPE I AND TYPE II PYRETHROID FORMULATIONS. L. Sylianco-Wu, M. Kallman, M. Wilson, W. Slikker, Jr., A. Hikal, S. Ali and R. Holson. Departments of Psychology and Pharmacology, University of Mississippi, University, MS and Reproductive and Developmental Toxicology Division, NCTR, Jefferson, AR.

There is presently available from Princeton Economics, Inc. (PEI; P.O. Box 400, Princeton, MA 01517) a low-cost and flexible system for experimental control and data acquisition for operant procedures. The system offers plain-English selections of all schedule parameters from an extensive series of menus and requires no computer programming by the experimenter. In addition, content-sensitive "Help" information is available for all functions. The system offers simultaneous control of up to four inputs (manipulanda) and eight outputs (food, shock, cue-lights, noise generators, etc.). The PEI software offers easy experimental design with all standard individual schedules, as well as with compound schedules such as multiple, mixed, chained, tandem, concurrent, and conjoint. Each compound schedule can include compound schedules as components. Schedule values can be changed during experimental sessions, and additional reinforcers can be delivered by the experimenter whenever desired. As a result, the software permits training and probe sessions as well as steady-state experiments. The author presently controls multiple and conjoint schedules in six chambers using a single AT-type computer configured with a 2-MB ramdisk and additional system interface hardware. The PEI system provides summary data after each session for response rate, as well as for response duration, and interresponse time. It also provides summary cumulative response recordings and frequency distributions of response duration and interresponse time. All data can be extensively identified and stored in ASCII format for subsequent parsing and analysis with third-party statistical programs. PEI offers hardware and software installation, personal instruction, and unlimited telephone software support. PEI also offers software customization. EFFECTS OF SCHEDULE OF REINFORCEMENT ON A PENTOBARBITAL DISCRIMINATION. S. H. Snodgrass and D. E. McMillan. University of Arkansas for Medical Sciences, Department of Pharmacology and Toxicology, Little Rock, AR. The purpose of this experiment was to determine the influence of the schedule of reinforcement on drug discrimination behavior of rats. Five rats were trained to press one lever in the presence of 10.0 mg/kg of sodium pentobarbital and to press another lever in

This investigation explored the behavioral and neurochemical toxicity of perinatal oral exposure to Ambush (Type I) and Pydrin (Type II), two pyrethroid formulations. Thirty-six female rats were mated and exposed to various pyrethroid formulations by oral gavage from the first gestational day until their pups (culled to 8/litter) were 12 days old. Six mothers were exposed daily to one of the following treatments: corn oil control, corn oi1+96% xylene, 1.25 mg/kg Pydrin (pesticidal ingredient fenvalerate), 0.125 mg/kg Pydrin, 4.0 mg/kg Ambush (pesticidal ingredient permethrin), or 0.4 mg/kg Ambush. Behavioral evaluations of locomotor activity, muscular coordination and passive avoidance learning were conducted on half of the pups from each litter (N = 24 pups/treatment condition). The other pups were sacrificed, brains were removed and sectioned into frontal cortex, hippocampus, caudate, and cerebellum for neurochemical assessment. The monoamines DA, DOPAC, 5-HIAA, 5-HT and HVA levels were determined and the amino acids aspartate, glutamate, glutamine, glycine, GABA, and taurine were determined for each of the brain regions. Gestational duration was shortened by exposure to the high doses of Pydrin and Ambush but only pups from the 4.0 mg/kg Ambush group were significantly lighter. No physical malformations were observed in pups from any of the treatment conditions, although the high Pydrin exposure condition resulted in a 4% death rate. Behavioral changes were seen for both locomotor activity and muscular coordination. The shape of across-session habituation of locomotion was different for the xylene and corn oil and the high dose Ambush groups. Both groups were less active on day 1 and more active on days 2 and 3 than the other pups. The high doses of Ambush and Pydrin produced slower intrasession habituation. Muscular coordination was improved slightly following low dose exposure to both pesticides and reduced following high dose exposures. Regional brain weights were normal for the cortex, cerebellum and caudate but the hippocampus was 64% heavier for pups treated with 4.0 mg/kg Ambush. Amino acid determinations indicated that the