N-cyclopropyl-1,3,5-triazine-2,4,6-triamine

Neurotoxicity

Administrative data

Endpoint:

neurotoxicity: acute oral

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2012/10/2 to 2013/04/17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 424 (Neurotoxicity Study in Rodents)

Version / remarks:

1997

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.6200 (Neurotoxicity Screening Battery)

Version / remarks:

1998

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

N-cyclopropyl-1,3,5-triazine-2,4,6-triamine

EC Number:

266-257-8

EC Name:

N-cyclopropyl-1,3,5-triazine-2,4,6-triamine

Cas Number:

66215-27-8

Molecular formula:

C6H10N6

IUPAC Name:

N2-cyclopropyl-1,3,5-triazine-2,4,6-triamine

Test material form:

solid: particulate/powder

Remarks:

off-white crystalline

Test animals

Species:

rat

Strain:

Sprague-Dawley

Remarks:

Crl:CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, NC.
- Age at study initiation: approximately 6 weeks old
- Weight at study initiation: 193-263 g for males and 139-193 g for females
- Fasting period before study: Animals were not fasted prior to dose administration to avoid potential confounding effects of inanition on behavior.
- Housing: Upon arrival, all animals were housed 2-3 per cage by sex for approximately 6 days. Thereafter, all animals were housed individually in clean, stainless steel, wire-mesh cages suspended above cage-board. The cage-board was changed at least 3 times per week. Animals were maintained in accordance with the Guide for the Care and Use of Laboratory Animals (National Research Council, 1996).
- Diet: PMI Nutrition International, LLC Certified Rodent LabDiet® 5002 was provided ad libitum throughout the study.
- Water: Reverse osmosis-treated (on-site) drinking water, delivered by an automatic watering system was provided ad libitum throughout the study.
- Acclimation period: minimum of 13 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22°C ± 3°C
- Humidity (%): 50% ± 20%
- Air changes (per hr): minimum of 10 fresh air changes per hour
- Photoperiod (hrs dark / hrs light): 12-hour light (0600 hours to 1800 hours)/12-hour dark photoperiod

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

CMC (carboxymethyl cellulose)

Details on exposure:

TEST SUBSTANCE FORMULATIONS PREPARATION:
The test substance formulations used for dose administration were prepared once as single formulations for each dose level, divided into aliquots for dispensation, and stored refrigerated, protected from light. The test substance formulations were stirred continuously throughout preparation, sampling, and dose administration.

VEHICLE:
The vehicle used in preparation of the test substance formulations and for administration to the control group was 0.5% carboxymethylcellulose (CMC) in sterile water. The vehicle suspension was prepared once for administration to the control group (Group 1) and for the preparation of test substance formulations; aliquots were dispensed to the control group and stored refrigerated, protected from light. The vehicle was mixed throughout preparation, sampling, and dose administration.

Dose volume: 10 mL/kg bw.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Prior to the initiation of dosing, quadruplicate samples for homogeneity and concentration analyses were collected from the top, middle, and bottom strata of each test substance formulation used for dose administration and from the middle stratum of the control formulation. One set of samples was subjected to the appropriate analyses. The remaining set of samples was stored refrigerated as back-up. All analyses were conducted using a validated high performance liquid chromatography method using ultraviolet absorbance detection.

Duration of treatment / exposure:

Single dose

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

2 000 mg/kg bw/day (actual dose received)

Remarks:

High dose group

Doses / concentrations 2

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

Remarks:

Mid dose group

Doses / concentrations 3

Dose / conc.:

500 mg/kg bw/day (actual dose received)

Remarks:

Low dose group

No. of animals per sex per dose:

10 animals/sex/dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Dose levels were selected based on the findings of a previous acute toxicity study (Merkel, 2004) and a preliminary acute neurotoxicity study (Herberth, Draft, WIL-639196).
- Rationale for animal assignment: A printout containing the animal numbers, corresponding body weights, and individual group assignments was generated based on body weight stratification in a block design. The animals were then arranged into groups according to the printout. Individual body weights at randomization were within ± 20% of the mean for each sex.

Examinations

Observations and clinical examinations performed and frequency:

All animals were observed twice daily, once in the morning and once in the afternoon, for mortality and moribundity. Clinical examinations were performed once daily on all animals. The absence or presence of findings was recorded for all animals. Individual body weights were recorded prior to dosing (on study day -7) and on study days 0-7 (daily), 14, and 15.
Individual food consumption was recorded prior to dosing (study day -7), on study days 0-7 (daily), and study day 14. FOB findings were recorded for all animals prior to the initiation of dosing (study day -6), at the time of peak effect (approximately 3 hours post-dosing) on study day 0, and on study days 7 and 14.
Locomotor activity (LMA) was assessed for all animals prior to the initiation of dose administration (study day -6), at the time of peak effect (approximately 3 hours post-dosing) on study day 0, and on study days 7 and 14.

Sacrifice and (histo)pathology:

On study day 15, 5-7 rats/sex/group were deeply anesthetized by an intraperitoneal injection of sodium pentobarbital and then perfused in situ with a 4.0% paraformaldehyde/0.1M phosphate-buffered solution; replacement animals were used, as needed. The central and peripheral nervous system tissues were dissected and preserved. Fixed brain weight and brain dimensions (length [excluding olfactory bulbs] and width) were recorded. Any observable gross changes and abnormal coloration or lesions of the brain and spinal cord were recorded. All remaining (nonselected) rats were euthanized by carbon dioxide inhalation following successful perfusion of the selected rats (except as necessary to replace any of the rats selected for in situ perfusion fixation), and discarded without macroscopic examination.

Many nerve tissues (brain, spinal cord, sural nerves, eyes etc.) were collected from all animals and were perfused in situ.

Statistics:

Each mean was presented with the standard deviation (S.D.) and the number of animals (N) used to calculate the mean. In addition, standard error (S.E.) was presented for body weight, food consumption, brain measurements, and locomotor activity data.
Statistics Conducted by WIL Research:
All statistical tests were performed using WTDMS™ unless otherwise noted. Analyses were conducted using two-tailed tests (except as noted otherwise) for minimum significance levels of 1% and 5%, comparing each test substance-treated group to the control group by sex. Body weight, body weight change, food consumption, continuous FOB, and brain weight and measurement data were subjected to a parametric one-way ANOVA (Snedecor and Cochran, 1980) to determine intergroup differences. If the ANOVA revealed significant (p<0.05) intergroup variance, Dunnett's test (Dunnett, 1964) was used to compare the test substance-treated groups to the control group. FOB parameters that yielded scalar or descriptive data and non-graded histopathologic findings were analyzed using Fisher’s Exact Test (Steel and Torrie, 1980).
Statistics Conducted by BioSTAT Consultants, Inc.:
All statistical analyses were conducted using SAS® version 9.2 (SAS Institute, Inc.,2002-2008), or higher.
All repeated measures analysis of variance (RANOVA) statistical analyses for total and ambulatory locomotor activity counts recorded during pretest and after dosing were conducted as follows. Each analysis endpoint was analyzed, by sex and session, with a RANOVA. The covariance structure across time was selected by comparing Akaike’s Information Criterion (AIC).
The monotonic dose-response relationship was evaluated using sequential linear trend tests based on ordinal spacing of dose levels. Nonmonotonic dose responses were evaluated whenever no significant linear trends were
detected but TRT and/or TRT*TIME interaction was significant at the 0.01 level.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Cyromazine-related clinical findings were limited to the high dose group. An increased incidence of red material around the nose was noted for the 2000 mg/kg bw males generally during study days 3-8 and on the day of euthanasia (study day 15). An increased incidence of decreased defecation and/or small feces were noted for the 2000 mg/kg bw females primarily during the first few days following dosing (study days 1 and/or 2); this finding correlated with the lower mean food consumption noted for these females during the same interval.
No test substance-related clinical observations were noted for the 250 and 1000 mg/kg bw males and females. Observations for the 250 and 1000 mg/kg bw animals occurred with similar incidence as in the control group, were limited to single animals, occurred in a non-dose-related manner, and/or were common findings for laboratory rats of this age and strain.

Mortality:

no mortality observed

Description (incidence):

All animals survived to the scheduled euthanasia on study day 15.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Test substance-related mean body weight losses were noted for the 1000 and 2000 mg/kg males and females during study day 0-1; differences from the control group were statistically significant. Lower mean body weight gains continued for the 1000 and 2000 mg/kg males during study day 1-2; the difference was statistically significant only at 2000 mg/kg. There was an absence of a body weight gain (0 g) noted for the 250 mg/kg males during study day 0-1 compared to a mean body weight gain in the control group (5 g); however, the difference was not statistically significant. Mean body weight gain for the 250 mg/kg males became equal to that of the control group on the second day following dosing (study day 1-2). Mean body weight changes for males and females in all dose groups were similar to controls throughout the remainder of the study (i.e., subsequent to study day 2), except for a statistically significantly higher mean body weight gain for 2000 mg/kg females during study day 3-4 that was considered transient. The initial
mean body weight losses and lower mean body weight gains noted for the 1000 and 2000 mg/kg males resulted in lower mean body weight gains in these groups for the cumulative intervals (study days 0-7 and 0-15); differences were statistically significant at 2000 mg/kg. However, mean body weight losses and lower mean body weight gains for the 250 and 1000 mg/kg groups were mostly limited to the first 2 days of the study and closely
correlated with lower dietary intake during the same period. In addition, lower mean absolute body weights (up to 5.8% and 10.6%, respectively) were noted for the 1000 and 2000 mg/kg males, as compared to the control group, throughout the study; differences were statistically significant for the 2000 mg/kg males during study days 2-6. Therefore, the body weight effects noted for the 1000 and 2000 mg/kg males were
considered adverse.
The initial mean body weight changes (during study days 0-1) for the 250 mg/kg males and the 1000 and 2000 mg/kg males and females were not of sufficient magnitude to affect cumulative mean body weight gains (study days 0-7 and 0-15) or mean absolute body weights (study days 7 and 15) in these groups beyond the second day of the study. Therefore, the initial mean body weight losses and/or lower mean body weight gains noted for these groups were not considered adverse.
Mean body weights and body weight gains for the 250 mg/kg females were unaffected by cyromazine administration. Differences from the control group were slight and not statistically significant.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Lower mean food consumption values were noted for the 1000 and 2000 mg/kg males and females during the first 2 days following dosing; differences from the control group were generally statistically significant. Lower mean food consumption was still evident in the rats of the highest dose of 2000 mg/kg 3 days following dosing; the difference was significant for males only. The mean food consumption for the 1000 mg/kg males and females were similar to or higher than the control group during study days 2-3. The initial lower mean food consumption noted for males in these groups correlated with the mean body weight losses and/or lower mean body weight gains noted during the same intervals. The initial reduction for the 2000 mg/kg males resulted in statistically significantly lower mean food consumption over the cumulative study days 0-7 interval, as shown in the text table below. The effects on mean food consumption noted for the 2000 mg/kg males were considered adverse. Mean food consumption for the 1000 and 2000 mg/kg males was similar to the control group from the third day following dosing to the end of the study. Food consumption for the 1000 and 2000 mg/kg females was similar to the control group over the study days 0-7 and 7-14 cumulative intervals.
Statistically significantly lower mean food consumption was noted for the 250 mg/kg males during study days 0-1 and was considered test substance-related. However, this change was not of sufficient magnitude to affect the cumulative food consumption interval over study days 0-7, and there were no corresponding effects on mean body weight gains following the first day of dosing. Therefore, the initial reduction in mean food consumption for the 250 mg/kg males was considered non-adverse. Mean food consumption for the 250 mg/kg females was unaffected by cyromazine administration. Differences from the control group were slight and not statistically significant.

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

Brain weights and measurements were unaffected by the administration of cyromazine at 250, 1000, and 2000 mg/kg bw. There were no statistically significant differences between the control and test substance-treated groups.

Gross pathological findings:

no effects observed

Description (incidence and severity):

No macroscopic changes were observed for animals at the scheduled necropsy on study day 15.

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

No test substance-related microscopic lesions were observed in any of the central or peripheral nervous system tissues examined from 5 animals/sex in the 2000 mg/kg bw group. All findings observed were consistent with normal background lesions in clinically normal rats of the age and strain used in this study and were considered spontaneous and/or incidental in nature and unrelated to test substance administration.
There were instances of axonal degeneration in the peripheral nerves and in the spinal nerves and spinal nerve roots. This axonal degeneration was of minimal severity, typically with only a single ‘digestion chamber’, and consistent with incidental alterations. Minimal axonal degeneration in the peripheral nerves and spinal nerve roots is a common background lesion (Eisenbrandt, et al., 1990).

Other effects:

effects observed, treatment-related

Description (incidence and severity):

Home cage parameters were unaffected by test substance administration. There were no statistically significant differences for the test substance-treated males and females when compared to the control group at the time of peak effect on study day 0, and on study days 7 and 14.
Handling parameters were unaffected by test substance administration. There were no statistically significant differences for the test substance-treated males and females when compared to the control group at the time of peak effect on study day 0, and on study days 7 and 14.
Open field parameters were unaffected by test substance administration.
Statistically significantly higher mean numbers of rears (10.1) were noted for the 2000 mg/kg females compared to the control group (5.0) on study day 7. However, the mean number of rears for the 2000 mg/kg females was within the range of values in the WIL historical control data (8.1 to 10.3) and similar to the number observed in the 250 mg/kg females on study day 7, while the mean number of rears in the concurrent control group was below the minimum mean value in the WIL historical control data. In addition, the mean number of rears for the 2000 mg/kg females was similar to the control group on study day 0. Therefore, the difference for the 2000 mg/kg females on study day 7 was not considered test substance-related.
There were no other statistically significant differences for the test substance-treated males and females when compared to the control group at the time of peak effect on study day 0, and on study days 7 and 14. For the 2000 mg/kg males, a higher (not statistically significant) mean time to first step (1.7 seconds) was noted compared to the control group (0.5 seconds) at the time of peak effect on study day 0. However, this was attributed to a single male in the 2000 mg/kg group with a time to first step of 10.3 seconds, and therefore was not considered test substance-related.
Sensory parameters were unaffected by test substance administration. There were no statistically significant differences for the test substance-treated males and females when compared to the control group at the time of peak effect on study day 0, and on study days 7 and 14.
Neuromuscular Observations: A test substance-related, statistically significantly lower mean hindlimb footsplay was noted for the 2000 mg/kg males (39.5 mm) compared to the control group (63.3 mm) at the time of
peak effect (approximately 3 hours following dose administration) on study day 0. In the absence of a persistent effect on this parameter (i.e., there were no test substance-related effects on mean hindlimb footsplay for males on study days 7 and 14) and because no neurohistopathologic lesions were noted, this finding was attributed to generalized systemic toxicity (as reflected by the marked body weight loss that was noted over the first day following dosing in this group).
No other test substance-related effects on neuromuscular parameters were noted for males in the 2000 mg/kg group. Although a statistically significantly lower mean hindlimb grip strength was noted for the 2000 mg/kg males (554.7 g) on study day 14, this difference was not considered test substance-related, but rather a reflection of a spuriously high mean control value on study day 14 (697.7 g). It should also be noted that the mean pre-test
hindlimb grip strength value for the 2000 mg/kg males was lower than the control value, there was no evidence of an effect on study day 7 (488.1 g in the control group compared to 475.8 g in the 2000 mg/kg males), and there were no corresponding neurohistopathologic findings.
Neuromuscular parameters were unaffected by test substance administration for the 250 and 1000 mg/kg males and the 250, 1000, and 2000 mg/kg females. There were no statistically significant differences for these groups when compared to the control group at the time of peak effect on study day 0, and on study days 7 and 14.
Physiological Observations: A statistically significantly lower mean body temperature was noted for the 2000 mg/kg males (36.2°C), as compared to the control group (37.2°C), at the time of peak effect (approximately 3 hours following dose administration) on study day 0, and was attributed to treatment. The mean body temperature value for the 2000 mg/kg males at the time of peak effect on study day 0 was also lower than the value in this group during the pretest period (36.7°C). In the absence of a persistent effect on this parameter (i.e., no test substance-related effects on mean body temperature for the 2000 mg/kg males on study days 7 and 14) and because no neurohistopathologic lesions were noted, this finding was attributed to generalized systemic toxicity (as reflected by the marked body weight loss that was noted over the first day following dosing in this group).
Lower mean body weights (not statistically significant) were noted for the 2000 mg/kg males on study day 7 (253.5 g) compared to the control group (273.1) and corresponded to the effects noted in this group at the weekly body weight intervals.
No other test substance-related effects on physiological observations were noted for the 2000 mg/kg males at the time of peak effect on study day 0. There were no physiological observational findings for the 2000 mg/kg males on study days 7 and 14.
Physiological parameters were unaffected by test substance administration for the 250 and 1000 mg/kg males and the 250, 1000, and 2000 mg/kg females. There were no statistically significant differences for these groups when compared to the control group at the time of peak effect on study day 0, and on study days 7 and 14.
Locomotor Activity: Test substance-related effects on locomotor activity (LMA) were observed in the 250, 1000, and 2000 mg/kg males and females at the time of peak effect on study day 0. Statistically significantly lower mean total and ambulatory LMA counts were noted for the 250, 1000, and 2000 mg/kg males, as compared to the control group, during the first LMA
subinterval (0-10 minutes) at the time of peak effect on study day 0. The mean cumulative total and ambulatory LMA counts (0-60 minutes) at the time of peak effect on study day 0 were statistically significantly lower for the 1000 and 2000 mg/kg males compared to the control group. The mean cumulative ambulatory LMA counts, but not total LMA counts, at the time of peak effect on study day 0 were statistically significantly lower for the 250 mg/kg
group males compared to the control group.
Statistically significantly lower mean total and ambulatory LMA counts were noted for the 250, 1000, and 2000 mg/kg females, as compared to the control group, during the first LMA subinterval (0-10 minutes) at the time of peak effect on study day 0. The mean cumulative total and ambulatory LMA counts (0-60 minutes) at the time of peak effect on study day 0 were statistically significantly lower for the 1000 and 2000 mg/kg females compared to the
control group. The mean cumulative total and ambulatory counts at the time of peak effect were not statistically significantly different for the 250 mg/kg females compared to the control group.
No cyromazine-related changes in mean total and ambulatory LMA counts were noted for males and females at any dose level on study days 7 and 14. Although statistically significantly lower mean cumulative total and/or ambulatory LMA counts were noted for females in the 250, 1000, and 2000 mg/kg groups on study day 7 and in the 1000 and 2000 mg/kg groups on study day 14, these changes did not occur in a dose-related manner and/or the mean values in the control group exceeded the maximum mean values in the WIL historical control data. Furthermore, the lower cumulative values noted in these groups were due to greater habituation of test substance-treated females, as activity in the treated groups was similar to the control group during the first 10-minute subinterval. Therefore, the lower mean cumulative total and ambulatory LMA counts noted for females on study days 7 and 14 were not considered test substance-related.
No remarkable shifts in the pattern of habituation occurred in any of the test
substance-treated groups when the animals were evaluated on study days 0, 7, and 14.

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

250 mg/kg diet

Based on:

test mat.

Sex:

male

Basis for effect level:

body weight and weight gain

food consumption and compound intake

other:

Target system / organ toxicity

Key result

Critical effects observed:

no

Any other information on results incl. tables

Results are provided in the overall remarks section below.

Applicant's summary and conclusion

Conclusions:

Following a single oral dose of cyromazine to male and female Crl:CD(SD) rats at 250,
1000, or 2000 mg/kg, the no-observed-effect level (NOEL) could not be determined based on the lower mean body weight gain and decreased food consumption that occurred over the first day of treatment, and the decreased cumulative ambulatory locomotor activity observed at time of peak effect for the 250 mg/kg males. The treatment-related findings for the 250 mg/kg males are not considered adverse; therefore the no-observed-adverse-effect level (NOAEL) is considered to be 250 mg/kg.
Statistically significant mean body weight losses and lower mean food consumption over the first day following treatment were noted for the 1000 and 2000 mg/kg males and females, as compared to controls. Test substance-related FOB and/or LMA findings were noted at the time of peak effect (approximately 3 hours postdose) for the 1000 and 2000 mg/kg males and females. Lower mean hindlimb footsplay and lower mean body temperature were noted for the 2000 mg/kg males, and lower cumulative total and ambulatory LMA counts were noted for the 1000 and 2000 mg/kg males and females.
The treatment-related FOB and LMA findings were transient (noted only at time of peak
effect) and were attributed to generalized systemic toxicity, as reflected by the lower mean body weight gains and lower food consumption over the first day(s) following treatment. No treatment-related FOB or LMA findings were observed on study days 7 and 14, and there were no treatment-related histopathology findings observed in the nervous system tissues of the 2000 mg/kg animals.

Executive summary:

Study Design:
The purpose of this study was to evaluate the acute neurotoxicity of cyromazine following a single oral dose to rats. Cyromazine was administered orally by gavage to groups of Crl:CD(SD) rats at dose levels of 250, 1000, or 2000 mg/kg. A concurrent control group received the vehicle (0.5% carboxymethylcellulose in water) on a comparable regimen. Animals were approximately 6 weeks old at the initiation of dosing. Each group consisted of 10 rats/sex. The dose volume was 10 mL/kg for all groups.
All animals were observed twice daily for mortality and moribundity. Clinical examinations were performed daily, except on days of functional observational battery (FOB) assessments. Individual body weights were recorded prior to dosing (study day -7) and on study days 0-7 (daily), 14, and 15; individual food consumption was recorded prior to dosing (study day -7), during study days 0-7 (daily), and study day 14. FOB and locomotor activity (LMA) data were recorded for all animals prior to dosing, at the time of peak effect (approximately 3 hours following dose administration) on study day 0, and on study days 7 and 14. On study day 15, five to seven surviving rats/sex/group were deeply anesthetized and perfused in situ; brain weights and brain dimensions (excluding olfactory bulbs) were recorded. A neuropathological evaluation of selected tissues from the central and peripheral nervous systems was performed on 5 animals/sex in the control and 2000 mg/kg groups. The remaining rats were euthanized and discarded without macroscopic examination following successful perfusion of the selected rats.

Results:
Administration of a single oral dose of cyromazine to rats at dose levels up to 2000 mg/kg (the limit dose for acute neurotoxicity testing) did not produce any mortality.
Test substance-related findings noted at 2000 mg/kg included clinical observations (red material around the nose for males and decreased defecation and small feces for females), mean body weight losses and decreases in mean body weight gains, and lower mean food consumption. The extent of the reduced body weight gain for the 2000 mg/kg males over the
first few days following dosing resulted in a statistically significantly lower mean body weight gain over the 2-week postdose observation period, relative to control. Test substance-related FOB and/or LMA findings were noted for the 2000 mg/kg animals at the time of peak effect (approximately 3 hours following dose administration) on study day 0. Statistically significantly lower mean hindlimb footsplay and lower mean body temperature were noted for the 2000 mg/kg males, as compared to the control group, at the time of peak effect on study day 0. Lower mean cumulative total and ambulatory LMA counts were noted for the 2000 mg/kg males and females at the time of peak effect on study day 0. There were no FOB or LMA findings for the 2000 mg/kg animals on study days 7 and 14. In the absence of any treatment-related neurohistopathologic findings at 2000 mg/kg, these transient FOB and LMA findings are likely a reflection of generalized systemic toxicity as evidenced by the marked body weight loss and decreased food consumption noted at 2000 mg/kg over the first day following treatment.
Test substance-related findings noted at 1000 mg/kg included mean body weight losses and decreased mean body weight gains and lower mean food consumption, primarily over the first 1 or 2 days following dosing. The extent of the reduced mean body weight gain for the 1000 mg/kg males and females over the first 1 or 2 days following dosing did not result in statistically significantly lower mean body weight gains over the 2-week postdose observation period. There were no treatment-related FOB findings. Test substance-related lower mean cumulative total and/or ambulatory LMA counts were noted at time of peak effect on study day 0 for the 1000 mg/kg males and females. There were no test substance-related LMA findings for males and females at 1000 mg/kg on study days 7 and 14. The transient LMA findings are likely a reflection of generalized systemic toxicity as evidenced by the body weight loss and decreased food consumption noted at 1000 mg/kg over the first day following treatment.
There were no test substance-related findings noted for the 250 mg/kg females. Test substance-related findings noted at 250 mg/kg were limited to males, and included a slight decrease in mean body weight gain (not statistically significant) and lower mean food consumption (statistically significant), relative to controls, over the first day following dosing. These slight, transient decreases in mean body weight gain and food consumption did not impact mean absolute body weights, and are not considered adverse. There were no test substance-related FOB findings. Lower mean cumulative ambulatory LMA counts were noted at time of peak effect on study day 0 for the 250 mg/kg males. However, mean cumulative total LMA counts were not affected by treatment at 250 mg/kg. There were no test substance-related LMA findings for males on study days 7 and 14. Since mean cumulative total LMA counts were not affected by treatment, the transient decrease in cumulative ambulatory LMA counts were not considered adverse, and is likely a reflection of generalized systemic toxicity as evidenced by the lower mean body weight gain and decreased food consumption noted for the 250 mg/kg males over the first day following treatment.
There were no test substance-related macroscopic or microscopic findings of the neural tissues or effects on mean brain weights or brain measurements.