Our results suggest that subtle autonomic dysfunction occurs even in PHD and EHD.

To investigate the role of sympathetic neurovascular reactivity in the gender differences of cutaneous, cold-induced vasomotor response, we compared direct (at the site of cooling) and indirect (at a site remote from the cooling site) response measured by laser Doppler (LD) flowmetry in 12 healthy males and 12 healthy females. The females underwent testing twice, once in the follicular and once in the luteal phase of the menstrual cycle. We measured LD flow before and during local cooling of one hand at 15°C. We found that local cooling evokes a significantly greater decrease in cutaneous LD flow in females than in males in direct as well as in indirect response conditions (p < 0.05). Comparing the response in females in the different phases of menstrual cycle, we obtained a significantly greater direct response to local cooling in the luteal phase than in the follicular phase (p < 0.05). In contrast, there was no menstrual-cycle-dependent difference in the indirect response to cold. The results of our study strongly indicate that sympathetic neural reactivity, as assessed by way of an indirect response to a cold stimulus, significantly contributes to gender differences in the response to local cooling. In contrast, the variation in microvascular responsiveness to cold exposure due to the menstrual cycle is most probably caused by local vascular mechanisms rather than by variation in sympathetic neural reactivity to local cooling.

K(ATP) channels play an important role in human cutaneous vasodilatation induced by ACh and SNP.

Altered autonomic nervous system (ANS) functioning in early stages of Huntington's disease (HD) has been suggested, presumably due to distorted high-order autonomic control. ANS functioning in the early stages of HD was further investigated. Laser-Doppler (LD) flux in the skin of the fingertips, heart rate (HR), HR variability, systolic and diastolic blood pressure were measured during rest and during a 6 min cooling of one hand at 15°C. Data of 15 presymptomatic gene mutation carriers (PHD), 15 early symptomatic HD patients (EHD), and two groups of 15 age- and sex-matched controls were compared. The area under the low frequency (LF) and high frequency (HF) bands of the HR variability spectrum were calculated. An augmented reduction of cutaneous LD flux was found in response to the direct cooling in the PHD group (37.5 ± 8.5% of resting value) compared to the PHD controls (67.27 ± 8.4%) (p < 0.05). In addition, the PHD group had higher (LF/(LF + HF) index of primary sympathetic modulation of the HR at rest (53.6 ± 3.3) compared to the EHD patients (39.7 ± 4.2) (p < 0.05). In the EHD group, a significantly smaller change of HR during cooling (100.26 ± 1.2%) was found compared to the EHD controls (95.9 ± 1.0%) (p < 0.05). The results are in line with the hypothesis that ANS dysfunction occurs even in PHD subjects. Further, they support the hypothesis that dysfunction of the high-order autonomic centres are involved in HD.

Our results confirm a local vasodilatory effect of applied CO2 therapy. This finding indicates its potential clinical use.