Developmental neurotoxicity study of styrene by inhalation in Crl‐CD rats

Abstract

This study was conducted to assess potential adverse functional and/or morphological effects of styrene on the neurological system in the F2 offspring following F0 and F1 generation whole-body inhalation exposures. Four groups of male and female Crl:CD (SD)IGS BR rats (25/sex/group) were exposed to 0, 50, 150, and 500 ppm styrene for 6 hr daily for at least 70 consecutive days prior to mating for the F0 and F1 generations. Inhalation exposure continued for the F0 and F1 females throughout mating and through gestation day 20. On lactation days 1 through 4, the F0 and F1 females received styrene in virgin olive oil via oral gavage at dose levels of 66, 117, and 300 mg/kg/day (divided into three equal doses, approximately 2 hr apart). Inhalation exposure of the F0 and F1 females was re-initiated on lactation day 5 and continued through weaning of the F1 or F2 pups on postnatal day (PND) 21. Developmental landmarks were assessed in F1 and F2 offspring. The neurological development of randomly selected pups from the F2 generation was assessed by functional observational battery, locomotor activity, acoustic startle response, learning and memory evaluations, brain weights and dimension measurements, and brain morphometric and histologic evaluation. Styrene exposure did not affect survival or the clinical condition of the animals. As expected from previous studies, slight body weight and histopathologic effects on the nasal olfactory epithelium were found in F0 and F1 rats exposed to 500 ppm and, to a lesser extent, 150 ppm. There were no indications of adverse effects on reproductive performance in either the F0 or F1 generation. There were exposure-related reductions in mean body weights of the F1 and F2 offspring from the mid and high-exposure groups and an overall pattern of slightly delayed development evident in the F2 offspring only from the 500-ppm group. This developmental delay included reduced body weight (which continued through day 70) and slightly delayed acquisition of some physical landmarks of development. Styrene exposure of the F0 and F1 animals had no effect on survival, the clinical condition or necropsy findings of the F2 animals. Functional observational battery evaluations conducted for all F1 dams during the gestation and lactation periods and for the F2 offspring were unaffected by styrene exposure. Swimming ability as determined by straight channel escape times measured on PND 24 were increased, and reduced grip strength values were evident for both sexes on PND 45 and 60 in the 500-ppm group compared to controls. There were no other parental exposure-related findings in the F2 pre-weaning and post-weaning functional observational battery assessments, the PND 20 and PND 60 auditory startle habituation parameters, in endpoints of learning and memory performance (escape times and errors) in the Biel water maze task at either testing age, or in activity levels measured on PND 61 in the 500-ppm group. Taken together, the exposure-related developmental and neuromotor changes identified in F2 pups f...

NTP‐CERHR Expert Panel Report on the reproductive and developmental toxicity of styrene

“…These kinds of non-specific developmental effects are often associated with maternal toxicity. Growth effects were observed in one generation of a multi-generation study in rats (Cruzan et al, 2005c) and mice (Ninomiya et al, 2000). These studies generally support the conclusions from the definitive studies that the developmental toxicity of styrene is minimal and only observed in the presence of maternal toxicity.…”

“…Four reports from one laboratory evaluated brain neurochemicals and offspring behavior in rats after gestational exposure to styrene (Kishi et al, 1992(Kishi et al, , 1995Katakura et al, 1999Katakura et al, , 2001, and another study compared styrene exposure during the gestational and lactation periods with regard to dopamine receptor binding and neonatal behaviors (Zaidi et al, 1985). A two-generation rat study included neurobehavioral assessments in F 2 offspring (Cruzan et al, 2005c). A study using pregnant hamsters and mice (Kankaanpää et al, 1980) included a single high dose in the mouse study and small numbers of animals in the hamster study and lacked information on maternal toxicity.…”

“…One of these studies was conducted by inhalation and the other via drinking water in rats according to regulatory guidelines in place at the time. The study by Cruzan et al (2005b) also included a developmental neurotoxicity component (Cruzan et al, 2005c) that was consistent with regulatory guidelines. One of these studies indicates growth effects at very high levels of exposure, but neither study demonstrated teratogenic or functional effects.…”

“…One of these studies indicates growth effects at very high levels of exposure, but neither study demonstrated teratogenic or functional effects. Cruzan et al (2005c) reported a developmental neurotoxicity study in Crl:CD s (SD)IGS BR rats that was part of a two-generation reproductive study (Cruzan et al, 2005b, summarized in Section 4.2.3). F 0 and F 1 males and females were exposed to styrene by inhalation at 0, 50, 150, or 500 ppm 6 hr/day, 7 days/week from at least 70 days before mating through GD 20.…”

“…Litters were culled to five male and five female pups on PND 4. Pups were monitored for growth and developmental landmarks, and the results are reported in the developmental neurotoxicity study (Cruzan et al, 2005c) discussed in Section 3.2.2.2. On PND 21, two F 1 pups/sex/group were randomly selected from each litter.…”