Trigeminocardiac Reflex by Mandibular Extension on Rat Pial Microcirculation: Role of Nitric Oxide

Abstract

In the present study we have extended our previous findings about the effects of 10 minutes of passive mandibular extension in anesthetized Wistar rats. By prolonging the observation time to 3 hours, we showed that 10 minutes mandibular extension caused a significant reduction of the mean arterial blood pressure and heart rate respect to baseline values, which persisted up to 160 minutes after mandibular extension. These effects were accompanied by a characteristic biphasic response of pial arterioles: during mandibular extension, pial arterioles constricted and after mandibular extension dilated for the whole observation period. Interestingly, the administration of the opioid receptor antagonist naloxone abolished the vasoconstriction observed during mandibular extension, while the administration of Nω-Nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, abolished the vasodilation observed after mandibular extension. Either drug did not affect the reduction of mean arterial blood pressure and heart rate induced by mandibular extension. By qRT-PCR, we also showed that neuronal nitric oxide synthase gene expression was significantly increased compared with baseline conditions during and after mandibular extension and endothelial nitric oxide synthase gene expression markedly increased at 2 hours after mandibular extension. Finally, western blotting detected a significant increase in neuronal and endothelial nitric oxide synthase protein expression. In conclusion mandibular extension caused complex effects on pial microcirculation involving opioid receptor activation and nitric oxide release by both neurons and endothelial vascular cells at different times.

Repeated Mandibular Extension in Rat: A Procedure to Modulate the Cerebral Arteriolar Tone

“…Previous data, in normotensive rats, demonstrated that a single brief (10 min) and passive ME caused a significant and prolonged decrease of MABP and HR and, in pial arterioles, a decrease of the diameter concomitant to ME followed by an increase after removing ME. Interestingly, these arteriolar responses have been found to be mediated by different mechanisms (Lapi et al, 2013 , 2014 ).…”

“…Mandibular extension (ME) was induced as previously described (Lapi et al, 2014 ). Briefly, an appropriately U-shaped spring device was placed between the superior and inferior dental arches of the rat.…”

“…A single mandibular extension (ME), consisting in a submaximal mouth opening for 10 min induced with an ad hoc dilator, has been shown to cause an unusually prolonged reduction (of almost 3 h) of heart rate (HR) and mean arterial blood pressure (MABP) (Lapi et al, 2013 , 2014 ) in normotensive anesthetized rats. Similar results have been detected in young volunteers (Brunelli et al, 2012 ).…”

“…Moreover, the effects are depend on the ME duration, 10 min ME resulting the optimal stimulus (Lapi et al, 2013 ). The initial brief vasoconstrictory response involves an opioid receptor-mediated mechanism, and the subsequent prolonged vasodilation is related to NO intracellular signaling (Lapi et al, 2014 ).…”

Functional Outcome Changes in Surgery for Pituitary Adenomas After Intraoperative Occurrence of the Trigeminocardiac Reflex

“… 5 , 8 , 12 , 27 – 28 , 45 – 67 In another context, it could been shown that the gender has an important influence on pituitary adenomas; especially in frequency and in disease patterns. 26 , 32 – 34 , 36 , 39 , 46 But for the TCR nothing is known about a gender-dependence in pituitary adenoma function. However, the effects of such adverse events as induced by the TCR on postoperative pituitary function have never been explored as well.…”