Adrenergic receptors in the forehead microcirculation

The aim of the current pilot study was to establish a procedure that would allow the investigation of microcirculatory changes in the oral cavity. The authors studied the effects of painful stimulation using dry ice (CO2). To investigate potential regional differences in the change of blood flow, recordings were made for the tongue and at the mucosa of the hard palate, lip, and oral vestibule. The authors investigated 26 patients divided into groups of younger subjects (10 men, 3 women; age range 21-31 y) and older patients (2 men, 11 women; age range 54-74 y). Mucosal blood flow (mBF) was obtained at the hard palate, at the tip of the tongue, on the midline of the oral vestibule, and at the lip. Measurements were made during rest and for 2 minutes after application of dry ice for a 10-second duration, using a pencil-shaped apparatus. Blood pressure, heart rate, cutaneous blood flow, transcutaneous partial pressure of carbon dioxiode (PCO2) and partial pressure of oxygen (PO2) were recorded. Mucosal blood flow increased at all sites in response to application of dry ice (p <0.001), with peak flow at 0.5 minute to 1.5 minutes after onset of stimulation. During the 1.5 minutes to 2 minutes, blood flow decreased at all measurement sites with a tendency to return to baseline. Heart rate, blood pressure, pCO2, PO2, and cutaneous blood flow did not show significant changes. Overall, responses in older patients showed more variance when compared with younger patients. Stimulation by dry ice appears to be an effective, noninvasive, and tolerable means to investigate mucosal blood flow at different mucosal sites. Preliminary data indicate different levels of responsiveness to painful cold stimulation at different sites on the oral and perioral mucosa; particularly, mucosal blood flow response at the tongue was least pronounced. Therefore, assessment of stimulated mucosal blood flow appears to be a promising tool to investigate the pathophysiology of a number of neurologic symptoms, eg, the burning mouth syndrome.

Section: Discussionmentioning

confidence: 99%

Oral mucosal blood flow following dry ice stimulation in humans

Heckmann

Hilz

Hummel³

et al. 2000

“…Noradrenaline was then iontophoresed (60s, 50#A) at the phentolamine and saline sites in counterbalanced order across subjects. In previous experiments, the 1-min iontophoresis of noradrenaline induced substantial vasoconstriction [6,13] and increased sensitivity to heat in capsaicintreated skin [6,8]. After monitoring blood flow for up to 10 min, sensitivity to heat was measured at experimental and control sites in the capsaicin-treated skin.…”

Section: Methodsmentioning

confidence: 99%

“…In previous experiments, the iontophoresis of phentolamine for 10 min blocked the normal vasoconstrictor response to noradrenaline in the skin of the forehead [13]. Starting 3 min after the iontophoresis, heat pain thresholds were measured at the iontophoresis site and at two control sites in the capsaicin-treated skin.…”

Section: Methodsmentioning

confidence: 99%

The effect of noradrenaline, angiotensin II and vasopressin on blood flow and sensitivity to heat in capsaicin-treated skin

Drummond

1998

The effect of iontophoretically applied noradrenaline, angiotensin II and vasopressin on blood flow and sensitivity to heat was investigated in the capsaicin-treated forearms of 52 healthy volunteers. Non-specific effects of a 4-min saline iontophoresis were investigated in another 19 subjects. Pretreatment with phentolamine inhibited vasoconstriction and thermal hyperalgesia to noradrenaline, indicating that alpha-adrenoceptors mediated these responses. The intensity of thermal hyperalgesia differed significantly across the following treatments: saline (heat pain threshold 1.1 degrees C lower than at control sites), angiotensin II (3.4 degrees C), noradrenaline (6.4 degrees C) and vasopressin (9.0 degrees C). Decreases in skin blood flow were significantly greater after the iontophoresis of noradrenaline (65% reduction from baseline) and vasopressin (68%) than after the iontophoresis of angiotensin II (45%). In contrast to the other two drugs, angiotensin II induced thermal hyperalgesia in proportion to the intensity of vasoconstriction. The findings suggest that iontophoretic currents induce minor non-specific thermal hyperalgesia. Angiotensin II appears to increase sensitivity to heat by an ischaemic mechanism, whereas an additional non-vascular influence contributes to thermal hyperalgesia induced by noradrenaline and vasopressin. These mechanisms could contribute to hyperalgesia in chronic inflammatory or neuropathic pain syndromes.

“…For example, in a previous study [1] in our laboratory, adrenergic agonists and antagonists were administered transcutaneously in the forehead by iontophoresis, and local vascular responses were monitored with laser Doppler flow probes. The findings showed opposing o~-and J3-adrenergic effects on skin blood flow, consistent with the presence of multiple sympathetic influences on facial blood flow during thermoregulation, emotional responses, and head pain [2].…”

Section: Received September 10 2000; Accepted As Revised May 4 2001mentioning

confidence: 99%

Facilitating laser Doppler measurements of cutaneous adrenergic vasoconstriction: a comparison of methods

Lipnicki

Drummond

2001

Detecting vasoconstriction in the skin of the human forearm is often difficult because cutaneous perfusion is usually low, even in the absence of vasoconstrictive agents. However, flow through "vasoconstricted" skin can be detected by increasing the background skin blood flow. The aim of the current study was to evaluate local warming and postocdusive reactive hyperemia as techniques for increasing background flow to facilitate laser Doppler measurements of cutaneous vasoconstriction in the forearm. Noradrenaline introduced by iontophoresis into the forearm of healthy volunteers initially reduced the peak hyperemic response (mean decrease in hyperemia 21 +/- 7%, p <0.01), compared with a saline control. However, vasoconstriction was unrelated to the dose of noradrenaline and was not detectable when the test was repeated, possibly because the peak of the normal hyperemic response decreased with repeated occlusions. When the forearm was warmed to 42 degrees C, noradrenaline introduced by iontophoresis produced dose-dependent vasoconstriction relative to saline control sites and skin not having undergone iontophoresis (greatest mean decrease 64 +/- 7%, p <0.001). Therefore, local warming is recommended over reactive hyperemia for facilitating laser Doppler recordings of cutaneous vasoconstriction in the human forearm.