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Inhibitory effect of deep peroneal nerve input on the ventricular extrasystoles induced by stimulation of the defence area in the rabbit

Guo Xueqin, Li Peng

Department of Physiology, Shanghai Medical University. Shanghai, China

Abstract

Experiments were carried out on rabbits anesthetized with urethane and chloralose. The animals were immobilized with gallamine triethiodide and maintained by artificial ventilation. Stimulation of the perifornix area of hypothalamus, the dorsal part of midbrain periaqueductal gray and the ventral portion of medulla evoked a pressor response, an increase in the femoral blood flow, pupillary dilatation, and other components of the defence reaction as well as ventricular extrasystoles (ventricular extrasystoles induced by stimulation of the hypothalamus, midbrain periaqueductal gray and ventral portion of the medulla are abbreviated by HVE, PVE and MVE respectively). If the hypothalamic and midbrain defence areas were stimulated simultaneously with subthreshold current, a significant pressor effect and ventricular extrasystoles could be induced. After electrolytic lesion of bilateral ventral medullary areas, blood pressure dropped, the pressor response induced by defence areas stimulation was attenuated and the HVE and PVE were abolished. These results suggest that the ventral medullary area receives convergentinputs from the hypothalamic and midbrain defence areas and may be an essential link in the efferent pathway for HVE and PVE. Ventricular extrasystoles induced by stimulating unilateral hypothalamic, midbrain and ventral medullary defence areas or induced by stimulating bilateral hypothalamic and midbrain defence areas could be inhibited by deep peroneal nerve (DPN) stimulation. The inhibitory effect of DPN stimulation on extrasystoles induced by unilateral stimulation of the ventral medullary area could be abolished by destroying the contralateral ventral medullary area. The inhibitory effect of DPN stimulation on PVE or MVE persisted after an oblique transection of the brain stem from the anterior border of the superior colliculi to the preoptic chiasma, but could be abolished by a transection from the anterior border of the superior colliculi to the anterior border of the pons. The inhibitory effect of DPN stimulation on HVE, PVE or MVE still existed after electrolytic lesion of the pituitary. It is suggested that the inhibitory effect of DPN stimulation on HVE, PVE and MVE does not depend upon the integrity of pituitary, but does depend upon the brain structures rostral to the midbrain. The ventral portion of the medulla also plays a part in the inhibitory effect of DNP stimulation.

Key words: Defence reaction;Ventricular extrasystole;Ventral medullary area;Hypothalamus;Midbrain periaqueduct gray

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Citing This Article：

Guo Xueqin, Li Peng. Inhibitory effect of deep peroneal nerve input on the ventricular extrasystoles induced by stimulation of the defence area in the rabbit. Acta Physiol Sin 1986; 38 (3): (in Chinese with English abstract).