Parasympathetic reflex vasodilation in the cerebral hemodynamics of rats

Abstract

We investigated the role of parasympathetic reflex vasodilation in the regulation of the cerebral hemodynamics, and whether GABAA receptors modulate the response. We examined the effects of activation of the parasympathetic fibers through trigeminal afferent inputs on blood flow in the internal carotid artery (ICABF) and the cerebral blood vessels (rCBF) in parietal cortex in urethane-anesthetized rats. Electrical stimulation of the central cut end of the lingual nerve (LN) elicited intensity- and frequency-dependent increases in ICABF that were independent of changes in external carotid artery blood flow. Increases in ICABF were elicited by LN stimulation regardless of the presence or absence of sympathetic innervation. The ICABF increases evoked by LN stimulation were almost abolished by the intravenous administration of hexamethonium (10 mg kg(-1)) and were reduced significantly by atropine administration (0.1 mg kg(-1)). Although the LN stimulation alone had no significant effect on rCBF, LN stimulation in combination with a blocker of the GABAA receptor pentylenetetrazole increased the rCBF markedly. This increase in rCBF was reduced significantly by the administration of hexamethonium and atropine. These observations indicate that the increases in both ICABF and rCBF are evoked by parasympathetic activation via the trigeminal-mediated reflex. The rCBF increase evoked by LN stimulation is thought to be limited by the GABAA receptors in the central nervous system. These results suggest that the parasympathetic reflex vasodilation and its modulation mediated by GABA receptors within synaptic transmission in the brainstem are involved in the regulation of the cerebral hemodynamics during trigeminal afferent inputs.

Neuroprotective Effects of Trigeminal Nerve Stimulation in Severe Traumatic Brain Injury

“…There is also evidence that the vasodilatory effect of the trigeminal nerve is mediated in part by the parasympathetic fibers from the sphenopalatine ganglion, with acetylcholine and vasoactive intestinal polypeptide (VIP) as mediators 51–53 . This pathway involves primarily V3 (mandibular nerve) as the afferent arm, and parasympathetic fibers via the sphenopalatine or otic ganglion as the efferent arm 51 .…”

“…This pathway involves primarily V3 (mandibular nerve) as the afferent arm, and parasympathetic fibers via the sphenopalatine or otic ganglion as the efferent arm 51 . It should be noted that this pathway was not specifically targeted in this study.…”

Differences in control of parasympathetic vasodilation between submandibular and sublingual glands in the rat

“…SMGBF and SLGBF on both sides were monitored using a laser speckle flow meter (Omegazone; Omegawave, Tokyo, Japan), which provides high-resolution twodimensional blood flow images in a matter of seconds, as described previously (8,18). As shown in Fig.…”

Effect of the parasympathetic vasodilation on temperature regulation via trigeminal afferents in the orofacial area

“…Changes in BF in the lower lip ( Fig. 1, iii) and skin of the dorsum of the foot on the left side were monitored using a laser speckle flowmeter (Omegazone; Omegawave, Tokyo, Japan), which obtains the high-resolution twodimensional images in seconds, as described previously [15,23,24]. A 780-nm semiconductor laser was used to illuminate the surface of the orofacial area.…”

“…For this purpose, the nerves were stimulated unilaterally under a binocular microscope. The LN was stimulated for 20 s using a supramaximal voltage (20 V) at various frequencies (1-20 Hz) for 2-ms pulse duration [15,17,24], either alone or in combination with CST stimulation (n = 6 in each group). Electrical stimulation of the CST was performed for periods of 2 min using a supramaximal voltage (10 V) and 2-ms pulse duration at various frequencies (0.5-5 Hz) [21].…”