Cre-mediated TrkB recombination in spinal cord motor neurons. (A) Lumbar spinal cord frozen sections from postnatal day 10, day 26 and 6-month ROSA 26 reporter mice expressing Cre under the control of the VAChT promoter were stained with X-gal and showed increased expression of Cre in adult ventral horn motor neurons. (B) Lumbar spinal cord frozen sections were stained with Neutral Red, and large neurons in the anterior horn were microdissected with PALM system (50×). (C) The same anterior horn was shown to indicate large spinal cord neurons before microdissection (200×). (D) The same anterior horn was shown after microdissection (200×). (E) Single-cell RT-PCR and nested PCR analyses of microdissected spinal cord neurons for TrkB (upper panel), Cre recombinase (middle panel) and ChAT (lower panel) expression. Cre-mediated recombination was seen in ChAT-positive (motor neuron) cells (lanes 1, 3, 12 and 15) as well as ChAT-negative cells (lanes 16, 17 and 19). (F) Summary of ChAT-positive specimens from RT-PCR/nested PCR.