Niacin biological challenge: A paradigm to evaluate social concerns.

BACKGROUND AND OBJECTIVES: Anxiety sensitivity (AS) social concerns, the fear of observable anxiety symptoms is posited as a risk factor for social anxiety by increasing fear reactivity in social situations when observable anxiety symptoms are present. Experimental evaluation of AS social concerns is limited. The current study utilized several manipulations designed to be relevant to AS social concerns or fear of negative evaluation (FNE), a distinct social anxiety risk factor. The effects of these manipulations on fear reactivity to a speech were examined. METHODS: Participants (N = 124 students; M age = 19.44, SD = 2.45; 64.5% female) were randomized to one of four conditions in a 2 (100 mg niacin vs 100 mg sugar pill) X 2 (instructional set) design. For the instructional set manipulation, participants were told their speech performance would be evaluated by a judge based on their performance (i.e., FNE-relevant) or their observable anxiety symptoms (i.e., AS social concerns-relevant). RESULTS: There was a main effect for vitamin condition with participants in the niacin condition reporting higher panic symptoms post-speech relative to those in the placebo condition. There was no main effect for speech instructions. As hypothesized, these effects were qualified by an interaction indicating that AS social concerns significantly predicted panic symptoms for those receiving niacin. LIMITATIONS: Limitations include the reliance on self-reports of outcome variables and the use of an undergraduate student sample. CONCLUSIONS: These findings highlight a distinct role of AS social concerns in fear responding to socially evaluative situations in the context of physically observable arousal.

Loratadine augments emotional blushing.

The aim of this study was to determine whether loratadine, a selective inverse agonist of peripheral histamine H1 receptors, would reduce emotional blushing. Loratadine (10 mg) or placebo was administered orally one hour before 31 healthy participants sang a children's nursery rhyme to evoke embarrassment and blushing. Skin blood flow was monitored via a laser Doppler probe attached to the cheek. Increases in facial blood flow while participants sang were greater in the loratadine than the placebo group (mean increase ±â€¯standard deviation 71 ±â€¯52% in the loratadine group versus 35 ±â€¯37%, p = .036). However, perceptions of blushing were similar in both groups. These findings suggest that loratadine augmented blushing rather than inhibiting it. Thus, histamine released during blushing may inhibit acute increases in facial blood flow by evoking H1 receptor-mediated vasoconstriction.

Topical ibuprofen inhibits blushing during embarrassment and facial flushing during aerobic exercise in people with a fear of blushing.

The flush that develops during whole-body heat stress depends partly on prostaglandins production in the skin. Variations in the strength of this local mechanism may contribute to individual differences in susceptibility to blushing and associated anxiety. To investigate this in the present study, the anti-inflammatory agent ibuprofen (which blocks prostaglandins formation) was applied topically to a small area of the cheek in 16 participants with a fear of blushing and in another 14 without this fear. Changes in skin blood flow were monitored at the ibuprofen-treated site and at a mirror image control site while participants sang (to induce embarrassment and blushing) and during aerobic exercise (to induce flushing). The topical ibuprofen treatment inhibited increases in cheek blood flow in both groups during both of these tasks. However, increases in cheek blood flow were greater in participants with high than low fear of blushing immediately after exercise. These findings suggest that prostaglandins contribute to dilatation of facial blood vessels both during emotional arousal (embarrassment) and aerobic exercise. Furthermore, fear of blushing may be associated with mechanisms that delay the resumption of normal vascular tone after a period of vasodilatation. Whether topical ibuprofen gel is suitable for intermittent or long-term use as an aid for blushing control requires further investigation.

The effect of niacin on facial blood flow in people with an elevated fear of negative evaluation.

The vasodilator niacin may provoke greater facial flushing and other symptoms of anxiety in patients with social anxiety disorder than in non-anxious controls. To determine whether this also applies in non-clinical samples, niacin (100mg) or placebo was administered double-blind to 33 young adults and flushing was investigated in relation to fear of negative evaluation (a cardinal feature of social anxiety). Increases in facial blood flow were greater in people with high than low fear of negative evaluation in the niacin condition, but were similar in both groups in the placebo condition. However, changes in pulse rate and ratings of embarrassment, anxiety, blushing and facial heat were similar in both groups in both drug conditions. These findings suggest that the facial vessels of people with a heightened fear of negative evaluation are particularly responsive to niacin under conditions of low anxiety and embarrassment.

The effect of adrenergic blockade on blushing and facial flushing.

The effect of adrenergic blockade on vascular responses in the forehead was assessed during stressful mental arithmetic, singing, and moderate exercise in 21 frequent blushers and 21 infrequent blushers. Adrenergic antagonists were introduced into a small site on the forehead by iontophoresis, and vascular responses were monitored bilaterally with laser Doppler flowmetry. Beta blockade prevented increases in blood flow in infrequent blushers during mental arithmetic and partially inhibited vasodilatation during singing, indicating minor participation of beta-adrenoceptors in blushing. Alpha blockade did not affect blushing but augmented vasodilatation during exercise. Despite higher ratings of self-consciousness in frequent than in infrequent blushers, vascular responses were similar in both groups. Thus, blushing propensity does not appear to be related to the density of alpha- or beta-adrenoceptors in facial vessels and may have a psychological basis.

Epoprostenol (prostacyclin,PGI2) increases apparent liver blood flow in man.

When epoprostenol (prostacyclin, PGI2) is given by infusion to man, cardiac output is increased, and it appears that the gastrointestinal tract may receive a disproportionate share of this. We have used the clearance of indocyanine green dye to estimate liver blood flow in 8 healthy subjects. During an infusion of PGI2 at a dose of 5 ng/kg/min, apparent liver blood flow increased from 925 +/- 220 ml/min (Mean +/- s.d) to 1320 +/- 453 ml/min, an average increase of 41.1%. Significant changes in heart rate, headache, facial flushing, systolic blood pressure, and pulse pressure were noticed. We suggest that endogenous epoprostenol (PGI2) may be of importance in the physiological regulation of liver blood flow in man. As this dose of epoprostenol could be tolerated readily, epoprostenol therapy could prove a therapeutic advance in some liver disorders, particularly liver transplantation, and possibly in the therapy of certain drug overdoses.

Chlorpropamide-alcohol flushing is not useful for individual genetic counseling of diabetic patients.

The presence or absence of chlorpropamide-alcohol flushing (CPAF) was not correlated with the classification of diabetes. Five out of twelve patients with juvenile-onset diabetes (JOD) flushed and three out of four patients with maturity-onset diabetes in young people (MODY) did not flush. Consequently, CPAF cannot be used for individual genetic counseling in diabetes mellitus.