Objective To study the protective effect of tetramethylpyrazine (TMP) on the respiratory inhibition induced by hypoxia. Methods Forty-four SD rats were used. The hypoxic rat model was established. The effects of TMP on the responses of respiratory activity and life time to hypoxia were observed. The Nissl's staining and immunohistochemical technique were used to investigate the effect of hypoxia on the Nissl's bodies and FOS expression in the brainstem and the antagonistic action of TMP. Results In contrast...