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neurotoxicity: sub-chronic inhalation
Type of information:
experimental study
Adequacy of study:
supporting study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Data on functional observation battery and motor activity after sub-chronic inhalation exposure in rats in GLP guideline study according to OECD TG422
Reason / purpose for cross-reference:
reference to same study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
other: OECD TG422
Principles of method if other than guideline:
Data on functional observation battery and motor activity after sub-chronic inhalation exposure in rats
GLP compliance:
BASF AG, Dept. of Toxicology
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
Isobutyl vinyl ether
EC Number:
EC Name:
Isobutyl vinyl ether
Cas Number:
Molecular formula:
isobutyl vinyl ether
Details on test material:
isobutyl vinyl ether (IBVE), purity >99.5% as determined by GC.
The stability under storage conditions over the exposure period was guaranteed.
Storage condition: refrigerator, stored under nitrogen.

Test animals

Details on test animals or test system and environmental conditions:
Wistar (CrlGlxBrlHan:WI) rats; female animals were nulliparous and non-pregnant
Source: Charles River, Germany
Housing: singly during the exposure period.
Free access to laboratory diet and tap water (analysed for contaminations) except during exposure and motor activity measurements.
Room: temperature 20-24°C
Relative air humidity 30-70%
Light/dark rhythm: 12 hrs.
Acclimatisation period: 6 or 13 days
Age st arrival: 4 or 5 weeks.

Administration / exposure

Route of administration:
other: air
Details on exposure:
Exposure to vapors of TS in an whole-body inhalation chamber (volume 1.4 m³) in individual cages in groups of 10 rats. For each concentration the test substance was supplied to a thermostated vapourizer at a constant rate by means of the metering pump; the vapour was generated with conditioned supply air (about 50% ± 20% relative humidity, 220 C ± 20 C) and passed into the inhalation system.
Analytical verification of doses or concentrations:
Details on analytical verification of doses or concentrations:
Concentration measurement by gas chromatography. At the beginning of the study, daily means were calculated based on 2 measured samples per concentration. Constancy in each inhalation system was continuously monitored by means of a total hydrocarbon analyzer. Correctness of hydrocarbon analyzer checked by GC. In the control group (test group 0) one sample per week was analyzed.
Duration of treatment / exposure:
13 weeks for males (93 days or 65 exposures and were sacrificed on the next workday after the last exposure)
15 weeks for females (67 to 72 exposures; sacrifice on study day 105)
13 weeks for satellite females (65 exposures in 92 days, sacrificed day 93)
Frequency of treatment:
5 days/week, 6 hrs/day
Doses / concentrationsopen allclose all
Doses / Concentrations:
0, 50, 500, 2000 ppm corresponding to 0, 208, 2080, 8300 mg/m³
nominal conc.
Doses / Concentrations:
0, 208+-9.8, 2095+-57, 8301+-58 mg/m³ (means +- SD)
analytical conc.
No. of animals per sex per dose:
10 male and 10 female rats per control and dose group but 5 males and 5 females for FOB and motor activity study.
5 females in satellite groups
Control animals:
yes, concurrent vehicle
Details on study design:
The males were treated for appr. 13 weeks (10 weeks premating, 3 weeks mating and post mating); females were treated during premating (10 weeks), mating and gestation through day 4 after delivery (approx. 15 weeks). Additionally a satellite group of female rats (5 animals per concentration, nuliparous and non-pregnant) were exposed 13 weeks.


Observations and clinical examinations performed and frequency:
OECD TG 422, including open field tests (functional observation battery and motor activity)
Specific biochemical examinations:
Details see Section 7.5.3
Neurobehavioural examinations performed and frequency:
A functional observational battery (FOB) and measurements of motor activity (MA) were carried out on study days 56 and 57 for males and females, respectively.

Home cage observations :
The animals were observed in their closed home cages ; any disturbing activities were avoided during these examinations in order not to influence the behavior of the animals. Attention was paid to:
1 . posture
2 . tremor
3 . convulsions
4 . abnormal movements
5 . impairment of gait
6 . other findings

Open field observations:
The animals were transferred to a standard arena (50 x 50 cm with sides of 25 cm high) and observed for at least 2 minutes. Following parameters were examined:
1 . behavior when removed from cage
2 . fur
3 . skin
4 . salivation
5. nose discharge
6. lacrimation
7. eyes/pupil size
8. posture
9. palpebral closure
10. respiration
11 . tremors
12. convulsions
13. abnormal movements
14. impairment of gait
15 . activity/arousal level
16. feces (number of fecal pellets/appearance/consistency) within two minutes
17. urine (appearance/quantity) within two minutes
18 . number of rearings within two minutes
19 . other findings

Sensorimotor Tests/Reflexes:
The animals were removed from the open field and subjected to following sensorimotor or
reflex tests :1 . approach response
2. touch response
3. vision ("visual placing response")
4. pupillary reflex
5. pinna reflex
6. audition ("startle response")
7. coordination of movements ("righting response")
8. behavior during "handling"
9. vocalization
10. pain perception ("tail pinch")
11 . grip strength of forelimbs
12. grip strength of hindlimbs
13. landing foot-splay test
14. other findings

Motor activity measurements (MA)
Motor activity was measured on the same day and with the same animals as FOB was performed . The measurement was performed in the dark using the Multi-Varimex-System with 4 infrared beams per cage. The numbers of beam interrupts were counted over 12 intervals, each lasting 5 minutes. Measurements ended exactly 60 minutes thereafter. During the measurements the animals received no food and no water.
Sacrifice and (histo)pathology:
Details see Section 7.5.3
KRUSKAL - WALLIS test (two-sided)
WILCOXON-test (two-sided)
level of significance p<=0.05

Results and discussion

Results of examinations

Details on results:
Neurofunctional tests: no biologically or statistically relevant findings noted in the FOB (Functional Observation Battery) and in motor activity test (MA) in any of the treatment groups compared with the control animal group.
Details on other endpoints are presented in Section 7.5.3.

Effect levels

Dose descriptor:
Effect level:
2 000 ppm
Basis for effect level:
other: (8300 mg/m³); highest dose level tested; NOAEC related to effects studied in FOB and motor activity; NOAEC local effects in the nasal cavity was 50 ppm (208 mg/m³)
Remarks on result:
other: Generation: other: - P (migrated information)

Applicant's summary and conclusion

Data on functional observation battery and motor activity after sub-chronic inhalation exposure in rats was given in a GLP guideline study according to OECD TG422. Even at the highest dose (2000 ppm or 8300 mg/m³) tested no effects were found concerning these parameters. However, the NOAEC for local effects in the nasal cavity was 50 ppm (208 mg/m³) and the LOAEC 500 ppm (2080 mg/m³).

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