Daily pattern of skin microcirculation in conscious laboratory rats

To study peripheral circulation without interference by anesthesia and surgical trauma, the analysis of red blood cell velocity (RBC; flying spot technique) and capillary diameters (diameter-cap; angiometer or ruler) in the depilated auricle of rats was proposed (Hertel, Microcirculation, Endothelium, and Lymphatics, 3, i.p., 1986). The rats were placed in plastic tubes and the right auricle was positioned on a transparent block with electronically controlled temperature using intravital microscopic techniques (transmitted light). For recording on video tape (U-matic), a video camera was mounted on top of the microscope. 8 Wistar Kyoto (WKY) and 8 spontaneously hypertensive (SHR) rats were analysed. RBC and diameter-cap were stored on video tapes in the course of 9 weeks from week 18 after birth every Monday during 8 am and noon and every Tuesday from noon to 4 pm; a second group of rats was treated vice versa. The experiments were performed from July to September 1986. In the animal h ousing facilities the photophase lasts from 7 am to 7 pm. The results were expressed as means +- SEM, the t-test for dependent samples (am/pm) was used. The data show that in conscious rats there is a statistically significant decrease in capillary diameters (WKY: p<0.005, SHR: p<0.10) and in RBC-velocity (WKY: p<0.01, SHR: p<0.05) in the afternoon compared to the values measured in the morning in the same animal. (ITA)