Evans Hooded Rats Research Articles

Long-term nitrogen dioxide exposure: effects on lung lipids and mechanical properties.

Male Long Evans hooded rats were chronically exposed to an average 2.9 ppm (±0.71 SD) of nitrogen dioxide 24 hours each day, five days a week for nine months. The major effects of NO2 were a significant 12.7% increase in lung wet weight, a 13.0% decrease in lung compliance, and a significant reduction in surface-active properties of the lung wash. The NO2-exposed lungs also revealed a significant 8.7% decrease in lung lipid content and a marked decrease in percentage of total saturated phospholipid fatty acids. This reduction in saturation was due almost entirely to a decrease in the percentage of palmitic acid. The suggestion is made that alterations in lung lipid metabolism may be the underlying mechanism which leads to some of the pulmonary effects following long-term exposure to subacute levels of NO2.

Apomorphine induced reinforcement

Under a 2 mg per kg intraperitoneal injection of apomorphine, four female Long Evans hooded rats were placed on continuous and fixed ratio reinforcement schedules using a gnawable pine block. Ss would learn to turn their heads away from the gnawable object in order to obtain 15 sec. of gnawing time. The rate of response increased from less than one response in 5 min. to over 3 responses per min. in 10 1½ hr. conditioning sessions. Rates of response stabilized during the last 5 experimental sessions and fixed ratio schedules of up to 5:1 were obtained in five additional 1½ hr. sessions.