Seasonal Climate Simulation in Rat Study

Twenty male specific-pathogen free (SPF)-grade Sprague–Dawley (SD) rats (age: 6 weeks; weight: 200 ± 20 g) were purchased from SPF (Beijing) Biotechnology Co., Ltd. Number of animal license: SYXK (Beijing) 2019–0010. This study was approved by the Ethics Committee of Beijing University of Chinese Medicine (approval number: BUCM-4-2,021,032,603-1,059).
All rats were adaptability housed for 7 days and randomly divided into four groups (n = 5 rats each) according to the method of the random number table. All rats were fed sterilized feed and deionized water in an artificial climate simulator (NHRHG6, Chongqing Hongrui Experimental Instrument Co., Ltd).
The artificial climate simulator uses a Balanced Temperature and Humidity Control (BTHC) system to control temperature (T) and relative humidity (RH). One can also design the corresponding parameters according to the actual environmental and climatic characteristics of the area and simulate the local climate. By strictly controlling environmental variable factors, the interference of other factors in experimental results can be reduced. Referring to the data¹ displayed by the Spanish National Meteorological Institute (Agencia Estatal de Meteorología, AEMET), select the China-Beijing area, we established the environment temperature for the four seasons based on the information about the average monthly maximum temperature for 2020. The temperatures of the four seasons were 14.8°C in spring, 26.2°C in summer, 12.9°C in autumn, and − 2.3°C in winter. Then, the relative humidity was established with reference to the average humidity of the natural season in 2020. Accordingly, the humidity of the four seasons was 40.3% in spring, 64.3% in summer, 52.2% in autumn, and 41.2% in winter.