1993 Volume 14 Issue Supplement Pages 561-564
Low power laser irradiation (LPLI) has been suggested to have various biological effects, but there are few reports about effects of direct LPLI to the brain. In the brain, cholinergic pathways are suggested to play a role in learning and memory functions. The medial septal nucleus and the vertical limb of diagonal band of Broca (septal complex) provide the major cholinergic projection to the hippocampus (Hpc), and the septal complex stimulation is reported to increase neural activities and local cerebral blood flow (LCBF) in the Hpc. The present study examined the effect of LPLI to the septal complex on the Hpc-LCBF. Adult male of Wistar strain rats were maintained under controlled lighting (lights on 5:00-19:00h) and temperature (24°C), and allowed free access to food and water. A 200-mm diameter polyurethane-coated platinum electrode with a 1-mm bare tip for measurement of LCBF and a stainless steel guide cannula for LPLI were introduced stereotaxically into the dorsal Hpc and the septal complex, respectively. The LCBF was measured by the hydrogen clearance method in freely moving rats. During LPLI, Hpc-LCBF increased by approximately 20% (p<0.01) as compared with the pretreatment control level, and kept an approximately 10% increase for 30 min after the LPLI. These results suggested that the LPLI enhanced the activity of cholinergic neurons in the septal complex and then caused an increase in the Hpc-LCBF.
