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To determine the neuronal connections in the periaqueductal gray (PAG) is important for studying modulation of neuronal activity of PAG to influence sympathetic responses. We had characterized projections from the left kidney to the midbrain PAG in adult male melanocortin-4 receptor (MC4R)-green fluorescent protein (GFP) transgenic mice by using retrograde tracing techniques of pseudorabies virus (PRV)-614 for direct visualization under two-photon immunofluorescence microscope. We found that injections of PRV-614 into the kidney resulted in retrograde infection of neurons in the ventrolateral sub-areas of PAG, and PRV-614/MC4R-GFP double-labeled neurons were detected in the ventrolateral sub-areas of PAG. These results indicated that a subpopulation of ventrolateral PAG neurons innervating renal tissues expressed MC4R, suggesting that deep brain stimulation of the ventrolateral PAG may influence renal function by melanocortinergic pathway.

OBJECTIVE: To measure relevant anatomical variables of lumbosacral nerve root and adjacent structures by magnetic resonance neurography (MRN) and analyze operative safety of transforaminal lumbar interbody fusion (TLIF) in Chinese subjects. METHODS: Twelve normal healthy volunteers (six men, six women) underwent MRN of lumbosacral nerve roots at 3.0 T. Three‐dimensional imaging was reconstructed with Osirix software and the following anatomic variables measured: (i) distance between nerve root and upper pedicle; (ii) distance between nerve root and lower pedicle; (iii) angle between nerve root and sagittal plane; (iv) distance between upper and lower nerve roots; and (v) distance between upper and lower pedicles. RESULTS: Good images of the L(1)‐L(5) nerve roots were obtained by MRN technology in all 12 volunteers. The distance between nerve root and upper pedicle and the angle between nerve roots and the sagittal plane gradually diminished from L(1) to L(5). However, there were no significant variations in the distance between nerve root and lower pedicle or between upper and lower pedicles. From L(1) (–2) to L(4) (–5), the distances between upper and lower pedicles, which are closely related to the operating space for TLIF in Chinese men and women, were less than 10 mm in most subjects and were significantly smaller in women than in men. The variables did not differ significantly between the left and right sides of the same segment. CONCLUSION: Based on the above anatomical study and measurement analysis, we believe that TLIF puts the upper nerve root at risk in some Chinese patients. However, this conclusion requires confirmation by anatomical study of large samples and clinical validation.