2015 Volume 50 Issue 1 Pages 48-53
Olfactory bulb (OB) is an attractive region for analyzing neural circuit in the brain. It has been so far well-examined by many researchers with special focus on interneurons in the OB. Recent progress in neuronal labeling and biological application by newly developed microscopes enable to reveal long-distance projection neuron from other brain regions to the OB as centrifugal input, which have not been analyzed for overall morphology becoming structural basis for understanding regulatory function to the OB neural circuit. By using combination of transgenic mice, genetic induction by viral vectors, multiple immuno-labeling, correlative laser and electron microscopies, digital tracing of a single neuron, and electron tomography, we have been analyzing centrifugal regulation to the OB neural circuit. In the review, we show our current and recent findings for serotonin neurons to the OB and discuss significance of presence of regulatory inputs to the OB from other brain regions. We further propose some possibilities in future analyses to be structural basis for neural circuit functions.