Axons of passage may be responsible for fastigial nucleus pressor response

Bilateral destruction of perikarya in the fastigial nucleus (FN) of the rat with the cytotoxic agent kainic acid (0.5 mg) did not alter the blood pressure (BP) increases observed during monopolar electrical stimulation (100 microA, 50 Hz, 0.5-ms pulse width) of this region. BP increases in control animals were 30 +/- 8 mm Hg, whereas BP increased 30 +/- 7 mmHg in kainic acid-lesioned rats. Furthermore, picrotoxin (100 ng) and muscimol (25 ng) microinjected unilaterally into the FN of conscious, unrestrained rats produced postural asymmetry but no change in BP or heart rate. These data suggest that the FN pressor response may be due, at least in part, to stimulation of axons of passage.