Long-lasting cardiovascular depression induced by acupuncture-like stimulation of the sciatic nerve in unanaesthetized rats. Effects of arousal and type of hypertension.

Prolonged low frequency stimulation of the sciatic nerve in conscious spontaneously hypertensive rats (SHR), is reported to induce a naloxone-reversible long-lasting depressor response (Yao et al. 1982a). In the present study this depressor response was compared during daytime and night-time conditions to determine whether different degrees of arousal affect this response. In addition, the effect of sciatic nerve stimulation was examined in one-clip, two-kidney renal hypertensive rats (RHR); a type of secondary hypertension which lacks the central autonomic hyper-reactivity which characterizes the SHR variant of primary hypertension. A maximal fall in blood pressure of 20 mm Hg was observed 1 h after sciatic nerve stimulation in SHR examined in daytime. We also found a significant bradycardia that lasted for 2.5 h. Neither poststimulatory depression nor bradycardia were observed in RHR examined at daytime. A short-lasting, non-significant decrease in blood pressure and heart rate was found following sciatic stimulation in SHR examined at night.