Parasympathetic reflex vasodilation in the cerebral hemodynamics of rats

• Published in: Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Biochemical, systemic, and environmental physiology, 2014-04, Vol.184 (3), p.385-399
• Main Authors: Ishii, Hisayoshi, Sato, Toshiya, Izumi, Hiroshi
• Format: Article
• Language: English
• Subjects: Anesthetics, Intravenous - pharmacology; Animal Physiology; Animals; Atropine - pharmacology; Biochemistry; Biomedical and Life Sciences; Biomedicine; Blood vessels; Carotid arteries; Carotid Artery, Internal - drug effects; Central nervous system; Cerebral Cortex - blood supply; Cerebral Cortex - physiology; Electric Stimulation; Ganglionic Blockers - pharmacology; Heart rate; Hemodynamics; Hexamethonium - pharmacology; Human Physiology; Intravenous administration; Life Sciences; Lingual Nerve - physiology; Male; Nervous system; Original Paper; Parasympatholytics - pharmacology; Rats; Rats, Wistar; Receptors, GABA - metabolism; Reflex - physiology; Regional Blood Flow - drug effects; Regional Blood Flow - physiology; Urethane - pharmacology; Vasodilation - drug effects; Veins & arteries; Zoology
• ISSN: 0174-1578; 1432-136X
• DOI: 10.1007/s00360-014-0807-2

We investigated the role of parasympathetic reflex vasodilation in the regulation of the cerebral hemodynamics, and whether GABA A 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 GABA A 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 GABA A 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.