Vasoactive intestinal polypeptide nullifies cytochrome reduction response to afferent activation of the perfused...

Redox states of cytochromes a(a3), b and c+c1 were continuously measured on the surface of the cerebral hemisphere of the perfused bullfrog brain with the aid of a scanning organ spectrophotometer. To correlate with changes of the redox state, electrical activity of the brain was simultaneously recorded in the vicinity of the tip of the light guide of the spectrophotometer. Electrical stimulation of the third dorsal root of the spinal cord induced parallel reduction of the cytochromes and burst activity in the brain. Intracerebroventricular (i.c.v.) infusion of vasoactive intestinal polypeptide (VIP; 30 pmol/100 g body weight) nullified the cytochrome reduction induced by the electrical stimulation of the dorsal root, but did not attenuate the burst activity. The i.c.v. infusion of VIP (30 pmol/100 g b.wt.) per se had little if any influence upon both redox state and burst activity. The infusion of 1 nM VIP into the internal carotid arteries also nullified the cytochrome reduction response to the afferent electrical activation. The present results provide evidence that one of the physiological roles of the VIPergic neurons in the brain may be to balance the redox states of electron transfer systems in neurons.