Kainic acid injection in NTS evokes hypertension and c-fos expression in spinal cord

Kainic acid injected into rat nucleus tractus solitarius (NTS) caused a slowly developing hypertension, with a 2-fold increase in Fos-immunoreactive (Fos-IR) nuclei in the area of the presympathetic bulbospinal neurons in the rostral ventrolateral medulla (RVLM) and a widespread activation of sympathetic preganglionic neurons (SPN) in the spinal cord, particularly in the mid to lower thoracic cord. The highest segmental concentration of Fos-IR SPN was in T8, with Fos-IR nuclei increased 12-fold compared with the vehicle injected group. More than 60% of retro-gradely labelled sympathoadrenal neurons in T8 were Fos-IR after kainic acid injection, consistent with the 60-fold increases in plasma adrenaline levels observed in these rats.