Effects Of The Chronic Cat Odor Exposure On The Behavior, Stress Hormone And The Expression Of Fos Of Norway Rats (Rattus Norvegicus)

This study was undertaken to confirm the effects of chronic cat odor exposure on the behavior, stress hormone and neurons activity of Norway rats breed in laboratory and Wistar rats which they have the same genetic background and different living environments by using the behavioral and physiological methods in laboratory, to analyze the effects of the environments on the adaptation ability of two types of rats, and to discuss the mechanism of rodents responding to the predator odor from behavior-hormone-neuron levels. The following results were obtained:1) The effects of chronic cat odor exposure on the behaviors of Norway rats and Wistar rats. For Norway rats breed in laboratory, acute cat odor exposure made their defensive behavior time and frequency (alert rearing time, alert rearing frequency, hiding time) significant increase and their non-defensive behavior time and frequency (exploring time, foraging frequency) significant decrease compared to the control group. The time and frequency of all behaviors became to the same as those of the control group with exposure time prolonged. The hiding time, grooming frequency and other behavior’time of female Norway rats were significantly higher than those of male, but the alert rearing time, exploring frequency and foraging frequency of female Norway rats were significantly lower than those of male. For Wistar rats, acute cat odor exposure made their defensive behavior time and frequency (alert rearing time, alert rearing frequency, hiding frequency) significant increase and their non-defensive behavior time and frequency (exploring time, foraging time, grooming time, other behavior’time, foraging frequency, grooming frequency, other behavior’frequency) significant decrease compared to the control group. The time and frequency of all behaviors also became to the same as those of the control group with exposure time prolonged. The alert rearing time, alert rearing frequency, hiding frequency of female Wistar rats were significantly higher than those of the male, but the hiding time, foraging frequency and other behavior’s frequency were lower than those of the male. The relative change rates of alert rearing time and grooming time for Norway rats were significantly higher than those for the Wistar rats, but the relative change rates of alert rearing frequency and foraging frequency for Norway rats were significantly lower than those for the Wistar rats.2) The effects of chronic cat odor exposure on the stress hormone of Norway rats and Wistar rats. Acute cat urine odor made the ACTH and CORT levels of both of Norway rats and Wistar rats in plasma significant increase compared to the control group. The ACTH and CORT levels of Norway rats and Wistar rats in plasma restored to the same as those of the control group with exposure time prolonged. The ACTH and CORT level of female Norway rats were significantly higher than those of the male. The relative change rate of ACTH for Norway rats was significantly lower than that for Wistar rats, but the relative change rate of CORT was significantly higher than that for Wistar rats.3) The effects of chronic cat odor exposure on the activity of Fos in four brain regions (AHP, VMHC, MeAD, BLA) of Norway rats and Wistar rats. For Norway rats, the activities of Fos in the four brain regions (AHP, VMHC, MeAD, BLA) under the cat odor exposure for different periods were significantly higher than those for the control group and they restored to the same as those of the control group with exposure time prolonged. The activity of Fos in MeAD for the female was significantly higher than that for the male. For Wistar rats, the activities of Fos in the four brain regions (AHP, VMHC, MeAD, BLA) under the cat odor exposure for different periods also were significantly higher than those for the control group. The relative change rate of the activity of Fos in AHP, VMHC, MeAD and BLA for Norway rats was significantly higher than that for Wistar rats.We concluded that both of Norway rats breed in laboratory and Wistar rats would produce responses from behavior, stress hormones and neuron activity when they were exposed to the acute predator odor. Norway rats failed to produce the adaptation of neuron activity, but Wistar rats produced the adaptation of neuron changes. The environment affected the sensitivity of behavioral, stress hormone and neuron activity response of Norway rats, reduced the relative change rate of the neuron activity of Wistar rats.