Bombesin-like immunoreactivity in the central nervous system of capsaicin-treated rats: a radioimmunoassay and immunohistochemical study.

ABSTRACT

The neuroanatomical distribution of bombesin-like immunoreactivity (BLI) in the rat central nervous system was investigated using radioimmunoassay and immunohistochemistry. Whereas cross-reactivity of the bombesin antiserum with substance P was problematic in the immunohistochemical experiments, no significant cross-reactivity with substance P was apparent in the radioimmunoassay. Results from the radioimmunoassay studies reveal particularly high concentrations of BLI in the hypothalamus, thalamus, medulla and spinal cord. Adult rats treated neonatally with capsaicin displayed significant depletions of somatostatin-like and substance P-like immunoreactivity and a small, statistically significant, reduction of BLI in the cervical spinal cord. Capsaicin treatment significantly reduced substance P-like immunoreactivity, but not somatostatin-like immunoreactivity, in the medulla and resulted in a small BLI depletion of borderline statistical significance in this brain region. Neonatally administered capsaicin treatment had no effect on the thalamic concentration of any of these three neuropeptides and neurotensin-like immunoreactivity was unchanged in all brain regions studied. These results suggest that the source of some of the BLI found in the spinal cord may be capsaicin-sensitive dorsal root ganglion cells.