An increase in cerebral blood flow elicited by electrical stimulation of the solitary nucleus in rats with cervical cordotomy and vagotomy.

Abstract

The effect of monopolar electrical stimulation of the intermediate portion of the solitary nucleus (SOL) on brain circulation was investigated in 48 anesthetized (N2O), artificially ventilated Wistar rats. The cervical spinal cord and bilateral vago-sympathetic trunks were severed to eliminate any change in arterial blood pressure mediated by the autonomic nervous systems on stimulating the SOL. Blood pressure was kept within the physiological range by intravenous phenylephrine infusion. Current intensity of the stimulus was set at 60+4uA (mean +S.E.; n=9), which was equivalent to 2.5 times threshold for vasopressin-induced pressor response. A sufficient dose of vasopressin-antagonist given to each rat shortly before determination of cerebral blood flow, prevented vasopressin-induced hypertension from stimulating the medulla. Stimulation elicited an increase in regional blood flow (14C-iodoantipyrine technique) by 72%, and 39 % on average in the frontal and occipital cortices, respectively, and 25% in the caudate-putamen (p<0.05; n=12 in control, and 9 in the stimulation studies). It was found that observed results included little detectable contribution from current spread of the stimulus toward the adjacent structures (dorsal medullary reticular formation and cuneate fasciculus) surrounding the SOL and from retrograde activation of the cerebellar fastigial nucleus. Overall, the present study suggests that a certain vasomotor mechanism, which is activated upon excitation of the intermediate portion of the SOL, regulates the blood vessels of the brain as a vasodilator.

The dynamics of physical exercise-induced increases in thalamic and abdominal temperatures are modified by central cholinergic stimulation

“…This hypothesis is supported by evidence that baroreflex stimulation modulates the activity of sympathetic fibers innervating the cerebral vessels [14,24] and that electrical stimulation of the nucleus of the solitary tract, the main area onto which baroafferents are projected, increases cerebral blood flow [14]. In addition, sinoaortic denervation, a surgical procedure that disrupts all afferents from the carotid and aortic baroreceptors, eliminates cerebral vasodilatation during acute hypertension induced by the infusion of phenylephrine in anesthetized rats [24].…”

“…Interestingly, the thermoregulatory effects mediated by Phy were consequent to the activation of aortic and carotid baroafferents [20], indicating that the increased cutaneous heat loss was not a "pure" thermoregulatory reflex triggered by central cholinergic stimulation. Because baroreflex activation also modulates blood flow in the brain [14,24], icv Phy is also expected to interfere with T brain regulation. However, the effects of Phy on brain thermal homeostasis are currently unknown.…”

Cerebral blood flow during exercise: mechanisms of regulation

“…Thus the arterial baroreflex mainly regulates arterial blood pressure such that it is maintained within the range of CA for cerebral circulation. However, anatomically, the autonomic nervous system via arterial baroreflex is directly linked to cerebral circulation (45,51,72,79,80). Several animal studies (45,51,72,79,80) have demonstrated close anatomical locations in the medulla acting as major control sites for both the cerebral and systemic circulation (i.e., the cardiovascular center).…”

“…However, anatomically, the autonomic nervous system via arterial baroreflex is directly linked to cerebral circulation (45,51,72,79,80). Several animal studies (45,51,72,79,80) have demonstrated close anatomical locations in the medulla acting as major control sites for both the cerebral and systemic circulation (i.e., the cardiovascular center). Unilateral electrical stimulation of the nucleus tractus solitarius increased CBF in rats with cervical cordotomy and vagotomy (79), whereas lesions within the nucleus tractus solitarius impaired CA (51).…”

Approach for quantifying the overall function of the ascending central neural integration to release vasopressin in rats.

“…Another test to exclude the possible current spreadding towards the fastigial nucleus was made by observing the vasopressin-induced pressor response when the nucleus was ablated. After ablation of the median one-third of the cerabellum (see NAKAI, 1985, for an illustration), electrical stimulation of 8 positions within the SOL still elicited the pressor response (see NAKAI, 1985, for a typical record). Vol.…”