Quantification of thyrotropin-releasing hormone changes and serotonin content changes following graded spinal cord injury.

Thyrotropin-releasing hormone (TRH) and serotonin (5-HT) are well known as neurotransmitters of descending bulbo-spinal tracts. 5-HT uptake caudal to (5-HT decreased) graded spinal lesions has been measured in rats and dogs and significantly correlated with the degree of cord injury. We studied 5-HT content via high-pressure liquid chromatography and radioimmunoassay measurements of TRH in dog spinal cord, both rostral and caudal, to 6 week T6 spinal transection (T) (n = 7) or T6 hemisections (H) (n = 7). Sham controls (n = 7) were used. Mean 5-HT content values were (pmole/mg): rostral sham 1.25 +/- 0.02, caudal sham 1.35 +/- 0.17, rostral T 2.65 +/- 0.36, caudal T 0.19 +/- 0.06, rostral H 2.1 +/- 0.22, and caudal H 1.0 +/- 0.31. A significant decrease in 5-HT caudal to transection versus control (P < 0.001) was seen. A trend for decreased 5-HT caudal to hemisection versus control (P < 0.1) was also seen. Mean TRH levels (pg/mg protein) were: rostral sham 40.02 +/- 18.47, caudal sham 30.61 +/- 10.03, brainstem sham 18.9 +/- 5.13, rostral T 52.4 +/- 21.34, caudal T 3.52 +/- 1.87, brainstem T 19.25 +/- 4.11, rostral H 43.45 +/- 18.61, caudal H 14.24 +/- 5.7, and brainstem H 21.89 +/- 1.23. Significant decreases for caudal TRH transection versus controls (P < 0.001) and for caudal TRH hemisection versus controls (P < 0.02) were seen. A significant difference between caudal hemisection and caudal transection TRH levels (P < 0.001) was seen.(ABSTRACT TRUNCATED AT 250 WORDS)