Duration of New-Onset Depressive Symptoms During Medical Residency.

Importance: The implications of new-onset depressive symptoms during residency, particularly for first-year physicians (ie, interns), on the long-term mental health of physicians are unknown. Objective: To examine the association between and persistence of new-onset and long-term depressive symptoms among interns. Design, Setting, and Participants: The ongoing Intern Health Study (IHS) is a prospective annual cohort study that assesses the mental health of incoming US-based resident physicians. The IHS began in 2007, and a total of 105 residency programs have been represented in this national study. Interns enrolled sequentially in annual cohorts and completed follow-up surveys to screen for depression using the 9-item Patient Health Questionnaire-9 (PHQ-9) throughout and after medical training. The data were analyzed from May 2023 to March 2024. Exposure: A positive screening result for depression, defined as an elevated PHQ-9 score of 10 or greater (indicating moderate to severe depression) at 1 or more time points during the first postgraduate year of medical training (ie, the intern year). Main Outcomes and Measures: The main outcomes assessed were mean PHQ-9 scores (continuous) and proportions of physicians with an elevated PHQ-9 score (≥10; categorical or binary) at the time of the annual follow-up survey. To account for repeated measures over time, a linear mixed model was used to analyze mean PHQ-9 scores and a generalized estimating equation (GEE) was used to analyze the binary indicator for a PHQ-9 score of 10 or greater. Results: This study included 858 physicians with a PHQ-9 score of less than 10 before the start of their internship. Their mean (SD) age was 27.4 (9.0) years, and more than half (53.0% [95% CI, 48.5%-57.5%]) were women. Over the follow-up period, mean PHQ-9 scores did not return to the baseline level assessed before the start of the internship in either group (those with a positive depression screen as interns and those without). Among interns who screened positive for depression (PHQ-9 score ≥10) during their internship, mean PHQ-9 scores were significantly higher at both 5 years (4.7 [95% CI, 4.4-5.0] vs 2.8 [95% CI, 2.5-3.0]; P < .001) and 10 years (5.1 [95% CI, 4.5-5.7] vs 3.5 [95% CI, 3.0-4.0]; P < .001) of follow-up. Furthermore, interns with an elevated PHQ-9 score (≥10) demonstrated a higher likelihood of meeting this threshold during each year of follow-up. Conclusions and Relevance: In this cohort study of IHS participants, a positive depression screening result during the intern year had long-term implications for physicians, including having persistently higher mean PHQ-9 scores and a higher likelihood of meeting this threshold again. These findings underscore the pressing need to address the mental health of physicians who experience depressive symptoms during their training and to emphasize the importance of interventions to sustain the health of physicians throughout their careers.

Impact of tetraplegia vs. paraplegia on venoarteriolar, myogenic and maximal cutaneous vasodilation responses of the microvasculature: Implications for cardiovascular disease.

Objective: Cardiovascular disease (CVD) is a leading cause of mortality in persons with SCI. While macrovascular remodeling and function after SCI is well documented, changes in the microvascular structure and function are comparably understudied, but importantly predict CVD risk. Specifically, the integrity of venoarteriolar (VAR), myogenic (MYO) and maximal vasodilation responses are largely unknown after SCI, especially in persons with tetraplegia (TP) at highest risk of CVD. This is the first to examine the differences in VAR (cuff inflation), MYO (limb dependency) and maximal vasodilation responses of the microvasculature between able bodied (AB) versus those with TP and paraplegia (PP).Design: Observational.Setting: Laboratory.Participants: Eight AB, 6 TP, and 8 PP persons.Interventions: One forearm and calf were treated topically with lidocaine 2.5%/prilocaine 2.5% while contralateral limb served as a control. Laser doppler flowmeters were applied over treated and control sites during limb dependency, cuff inflation and local skin heating (Tloc) up to 42°C.Outcome measures: Skin vascular resistance (SkVR) change with cuff inflation and limb dependency and maximal cutaneous vascular conductance (CVC) during local heating.Results: Change in SkVR was not significantly different between groups or extremity (upper vs. lower) during cuff inflation or limb dependency. However, CVC at Tloc 42°C was significantly different in the lower extremity (LE) of TP and PP (P = 0.007, 0.35) compared to AB.Conclusion: Increases in SkVR during cuff inflation (VAR) and limb dependency (VAR and MYO) are unaltered after SCI, however maximal vasodilation in the LE post-SCI is higher than AB persons.

Altitude and risk of depression and anxiety: findings from the intern health study.

Multiple studies suggest that the risks of depression and suicide increase with increasing altitude of residence, but no studies have assessed whether changing altitude changes these risks. To address this gap, this study used data from the Intern Health Study, which follows students from the end of medical school through the first year of residency, recording depression via the 9-item Patient Health Questionnaire (PHQ-9), anxiety via the 7-item Generalized Anxiety Disorder Questionnaire (GAD-7), and multiple risk factors for these symptoms. Data from 3764 medical students representing 46 schools and 282 residencies were available. Odds ratios (OR) representing the effects of altitude on psychiatric symptoms were estimated using generalized linear models. After excluding participants with missing altitude data, 3731 medical students were analyzed. High altitude residence (> 900 m) was significantly associated with PHQ-9 total score (OR = 1.32, 95% CI = 1.001-1.75, p < 0.05), and PHQ-9 suicidal ideation (OR = 1.79, 95% CI = 1.08-0.02, p = 0.02). Moving from low to high altitude was significantly associated with PHQ-9 total score (OR = 1.47, 95% CI = 1.087-1.98, p = 0.01), GAD-7 total score (OR = 1.40, 95% CI = 1.0040-1.95, p < 0.05), and PHQ-9 suicidal ideation (OR = 1.10, 95% CI = 1.01-1.19, p = 0.02). The data suggest that moving from low to high altitude is associated with increasing symptoms of depression, anxiety, and suicidal ideation.

Randomized, Double-Blind, Placebo-Controlled Trial Demonstrates the Efficacy and Safety of Oral Aripiprazole for the Treatment of Tourette's Disorder in Children and Adolescents.

OBJECTIVES: Aripiprazole modulates dopaminergic and serotonergic pathways that may play a role in the pathogenesis of Tourette's disorder (TD). This trial evaluated the efficacy and safety of oral aripiprazole in the suppression of tics in children and adolescents with TD. METHODS: This phase 3, randomized, double-blind, placebo-controlled trial ( ClinicalTrials.gov , NCT01727700) recruited patients who were 7-17 years old with a diagnosis of TD from hospitals, private practices, and research clinics at 76 sites in the United States, Canada, Hungary, and Italy. Patients were randomized in a 1:1:1 ratio by using an interactive voice/web-response system to low-dose aripiprazole (5 mg/day if <50 kg; 10 mg/day if ≥50 kg), high-dose aripiprazole (10 mg/day if <50 kg; 20 mg/day if ≥50 kg), or placebo for 8 weeks. Randomization was stratified by region (North America or Europe) and baseline body weight (<50 kg vs. ≥50 kg). The primary efficacy endpoint was mean change from baseline to week 8 in the Yale Global Tic Severity Scale Total Tic Score (YGTSS-TTS) for the intent-to-treat population. RESULTS: Between November 2012 and May 2013, 133 patients were recruited and randomized to low-dose aripiprazole (n = 44), high-dose aripiprazole (n = 45), or placebo (n = 44). Least-squares mean treatment differences versus placebo in change from baseline to week 8 in the YGTSS-TTS were statistically significant (high dose, -9.9 [95% confidence interval, CI, -13.8 to -5.9], low dose, -6.3 [95% CI, -10.2 to -2.3]). At week 8, 69% (29/42) of patients in the low-dose and 74% (26/35) of patients in the high-dose aripiprazole groups demonstrated a Clinical Global Impression-Tourette's Syndrome improvement score of 1 (very much improved) or 2 (much improved) compared with 38% (16/42) in the placebo group. The most common adverse events (AEs) were sedation (low dose, 8/44 [18.2%], high dose, 4/45 [8.9%], placebo, 1/44 [2.3%]), somnolence (low dose, 5/44 [11.4%], high dose, 7/45 [15.6%], placebo, 1/44 [2.3%]), and fatigue (low dose, 3/44 [6.8%], high dose, 7/45 [15.6%], placebo, 0). No serious AEs or deaths occurred. CONCLUSIONS: This study indicates that oral aripiprazole is a safe and effective treatment for tics in children and adolescents with TD.

Early antipsychotic response to aripiprazole in adolescents with schizophrenia: predictive value for clinical outcomes.

OBJECTIVE: In adults with chronic schizophrenia, most symptom decreases occur in the first few weeks of antipsychotic treatment, and nonresponse at week 2 predicts a later nonresponse. The trajectory of antipsychotic response and the predictive value of early antipsychotic effects were investigated for ultimate outcome in adolescent schizophrenia, where such data are still lacking. METHOD: This post hoc analysis of a 6-week, randomized, double-blinded trial of aripiprazole (n = 196) versus placebo (n = 98) evaluated if adolescents 13 to 17 years old with schizophrenia exhibited substantial symptomatic improvement to aripiprazole in the first few treatment weeks and whether early response (ER) versus early nonresponse (ENR) predicted clinically relevant outcomes. ER decreased at least 20% and ENR decreased less than 20% in Positive and Negative Syndrome Scale (PANSS) total score at week 2 (ER2/ENR2) or 3 (ER3/ENR3). Ultimate response decreased at least 40% in PANSS score. RESULTS: Nearly 50% of the PANSS decrease was achieved by week 2 and up to 75% by week 3. ER2/ER3 subjects showed significantly greater improvement than ENR subjects in PANSS total score, PANSS positive and negative subscale scores, and functionally relevant outcomes. In general, ER3 had better sensitivity, specificity, and positive and negative predictive values than ER2 for predicting ultimate response. ER2 subjects were 8.8 times (95% confidence interval 4.0-19.4) and ER3 subjects were 8.6 times (95% confidence interval 4.5-16.6) more likely to achieve remission at week 6 (p < .0001) than ENR2 and ENR3 subjects, respectively, although adverse events were similar. CONCLUSIONS: Like adults with chronic schizophrenia, adolescents with early-phase schizophrenia exhibited most symptomatic improvement early during aripiprazole treatment, with week 3 improvements having the best predictive power. Although requiring extension, these results may inform clinical decision making. Clinical trial registration information-Aripiprazole in Adolescents with Schizophrenia, http://clinicaltrials.gov/, NCT00102063.

Hospitalisation rates in patients switched from oral anti-psychotics to aripiprazole once-monthly for the management of schizophrenia.

OBJECTIVE: To report the design and preliminary results of a mirror-image study comparing total psychiatric hospitalisation rates pre- and post-switch to aripiprazole once-monthly, an extended release injectable solution. METHODS: A multi-center, open-label mirror-image study of patients (18-65 years) with schizophrenia to compare total psychiatric hospitalisation rates between retrospective treatment with oral standard-of-care (SOC) anti-psychotics and prospective treatment with aripiprazole once-monthly in a naturalistic community setting in North America. Total psychiatric hospitalisation rates were assessed between retrospective (Months -4 to -1) and prospective treatment periods (Months 4-6) for patients who completed ≥3 months aripiprazole once-monthly. RESULTS: One hundred and eighty-three patients entered the prospective phase. After switching to aripiprazole once-monthly, total psychiatric hospitalisation rates for the 3-month prospective period were significantly lower (p < 0.0001, Exact McNemar's test) compared with the retrospective 3-month period when the same patients received SOC anti-psychotics (6.6% [n = 8/121] vs 28.1% [n = 34/121], respectively; rate ratio = 0.24). Similarly, total psychiatric hospitalisation rates for all patients who entered the prospective treatment phase were significantly lower (p < 0.0001, Exact McNemar's test) for the prospective 6 months following switch to aripiprazole once-monthly, compared with the retrospective 6-month SOC period (14.2% [n = 26/183] vs 41.5% [n = 76/183], respectively; rate ratio = 0.34). Common treatment-emergent adverse events (occurring in ≥5% of patients) were psychotic disorder (7.7%), akathisia (7.2%), and insomnia (7.2%). Discontinuation (all causes) during the prospective phase was 44.8% (n = 82/183). LIMITATIONS: Mirror-image studies do not include a parallel active control; as each patient serves as their own control, it cannot be determined whether other treatments may have similar effects. Treatment and trial effects may be difficult to separate. Independent factors such as admission patterns, insurance coverage, availability of hospital beds, and community support may influence rates of hospitalisation. CONCLUSIONS: Switching to aripiprazole once-monthly substantially reduced total psychiatric hospitalisation rates compared with retrospective rates in the same patients taking oral SOC.

Clinical significance of treatment effects with aripiprazole versus placebo in a study of manic or mixed episodes associated with pediatric bipolar I disorder.

OBJECTIVE: Published studies in adult and pediatric bipolar disorder have used different definitions of treatment response. This analysis aimed to compare different definitions of response in a large sample of children and adolescents. METHODS: Anexploratory analysis of a 4-week, multicenter, placebo-controlled study assessed patients (n=296; ages, 10-17 years) with an acute manic/mixed episode associated with BIPOLAR I disorder who were randomized to aripiprazole (10 or 30 mg/day) or placebo. The primary efficacy endpoint was mean change from baseline to week 4 in young mania rating scale (YMRS) total score. Additional assessments included: clinical global impressions-bipolar disorder (CGI-BP) Overall and mania scales, child global assessment scale (CGAS), and parent and subject general behavior inventory. Response was compared across seven operational definitions. Cohen's κ and Spearman's correlation tested relationships between various response definitions or changes in outcome measures and clinically meaningful improvement (defined as a CGI-BP overall improvement score of 1 or 2). RESULTS: Response rates varied depending upon the operational definition, but were highest for 95% reliable change (statistical method used to determine individual change from previous assessment) and ≥33% reduction in YMRS total score. Response rate definitions with the highest validity in terms of predicting clinically meaningful improvement were: ≥50% reduction on YMRS (κ=0.64), a composite definition of response (YMRS <12.5, children's depression rating scale-revised (CDRS-R) ≤40, and CGAS ≥51; κ=0.59), and 95% reliable change on the CGAS or 33% reduction on YMRS (κ=0.56). Parent ratings of symptoms were generally better at detecting symptom improvement than were subject ratings (κ=∼0.4-0.5 vs. ∼0.2 when compared with CGI-BP overall improvement score). CONCLUSIONS: Clinically meaningful definitions of response in acute treatment of a manic/mixed episode in pediatric subjects include a 50% change in YMRS and a composite measure of response. Parent-reported measures of symptom improvement appear reliable for assessing symptom change.

Respondent and item level patterns of response of aripiprazole in the acute treatment of pediatric bipolar I disorder.

BACKGROUND: Few studies have evaluated the value of a parent- and subject-rated scale in detecting symptom change in response to pharmacologic treatment. METHODS: This was a post-hoc analysis of data from a 4-week, randomized, double-blind, placebo-controlled study to evaluate which informants detect response to treatment with aripiprazole in pediatric subjects experiencing a mixed or manic episode associated with bipolar I disorder. Efficacy assessments included clinician-rated scales and the parent- and subject-rated 10-item General Behavior Inventory Mania (GBI-M10) and Depression (GBI-D10) scales. Cohen's d quantified effect sizes for total scale scores and individual line items. RESULTS: Parent-GBI-M10 total, clinician-rated Young Mania Rating Scale (YMRS) total, and Clinical Global Impression-Bipolar Disorder (CGI-BP) Mania scores produced similar effect sizes, suggesting that the parent-GBI-M10 is sensitive to treatment-related improvements in manic symptoms. Aripiprazole improved a broad spectrum of parent-rated mania symptoms; six parent-GBI-M10 line item effect sizes were moderate (>0.5) in at least one of the two aripiprazole treatment arms (10 or 30 mg/day). Subject-completed GBI-M10 line item effect sizes were consistently smaller, indicating that the subjects' experience of treatment effects were less pronounced. LIMITATIONS: Study inclusion/exclusion criteria may limit generalizability of these findings. CONCLUSIONS: Parent ratings of mania severity were in agreement with clinician ratings, indicating that parent-rated assessments can be valuable in detecting symptom change over the course of treatment. These data support the use of the parent-GBI-M10 as an outcome measure in research and clinical settings.

Nitric oxide and receptors for VIP and PACAP in cutaneous active vasodilation during heat stress in humans.

VPAC2 receptors sensitive to vasoactive intestinal polypeptide (VIP) and pituitary adenylyl cyclase activating polypeptide (PACAP), PAC1 receptors sensitive to PACAP, and nitric oxide (NO) generation by NO synthase (NOS) are all implicated in cutaneous active vasodilation (AVD) through incompletely defined mechanisms. We hypothesized that VPAC2/PAC1 receptor activation and NO are synergistic and interdependent in AVD and tested our hypothesis by examining the effects of VPAC2/PAC1 receptor blockade with and without NOS inhibition during heat stress. The VPAC2/PAC1 antagonist, pituitary adenylate cyclase activating peptide 6-38 (PACAP6-38) and the NOS inhibitor, N(G)-nitro-l-arginine methyl ester (l-NAME) were administered by intradermal microdialysis. PACAP6-38, l-NAME, a combination of PACAP6-38 and l-NAME, or Ringer's solution alone were perfused at four separate sites. Skin blood flow was monitored by laser-Doppler flowmetry at each site. Body temperature was controlled with water-perfused suits. Blood pressure was monitored by Finapres, and cutaneous vascular conductance (CVC) calculated (CVC = laser-Doppler flowmetry/mean arterial pressure). The protocol began with a 5- to 10-min baseline period without antagonist perfusion, followed by perfusion of PACAP6-38, l-NAME, or combined PACAP6-38 and l-NAME at the different sites in normothermia (45 min), followed by 3 min of whole body cooling. Whole body heating was then performed to induce heat stress and activate AVD. Finally, 58 mM sodium nitroprusside were perfused at all sites to effect maximal vasodilation for normalization of blood flow data. No significant differences in CVC (normalized to maximum) were found among Ringer's PACAP6-38, l-NAME, or combined antagonist sites during normothermia (P > 0.05 among sites) or cold stress (P > 0.05 among sites). CVC responses at all treated sites were attenuated during AVD (P < 0.05 vs. Ringer's). Attenuation was greater at l-NAME and combined PACAP6-38- and l-NAME-treated sites than at PACAP6-38 sites (P > 0.05). Because responses did not differ between l-NAME and combined treatment sites (P > 0.05), we conclude that VPAC2/PAC1 receptors require NO in series to effect AVD.

Young mania rating scale line item analysis in pediatric subjects with bipolar I disorder treated with aripiprazole in a short-term, double-blind, randomized study.

OBJECTIVE: The aim of this study was to evaluate the effects of aripiprazole treatment on individual Young Mania Rating Scale (YMRS) line items in pediatric subjects with manic or mixed episodes associated with bipolar I disorder to better understand the discrete symptom improvements. METHODS: This was a post hoc analysis of the YMRS line item data from a 4-week, multicenter, randomized, double-blind, placebo-controlled study. Two hundred ninety-six eligible subjects were randomized to aripiprazole 10 mg/day (n = 98), aripiprazole 30 mg/day (n = 99), or placebo (n = 99). The primary endpoint was the mean change in YMRS total scores from baseline to week 4. Effect sizes and treatment effect on individual line items were calculated. RESULTS: Of the 296 subjects, 237 (80.1%) completed the 4-week study. Seven of the 11 YMRS line items showed a statistically significant improvement in both aripiprazole treatment groups versus placebo. Using the data for the pooled doses, the three YMRS line items with the greatest effect size at week 4 were irritability (effect size = 0.7; treatment effect = 1.43; p < 0.001), aggressive behavior (effect size = 0.7; treatment effect = 1.38; p < 0.001), and increased motor activity/energy (effect size = 0.6; treatment effect = 0.86; p < 0.001). CONCLUSION: Aripiprazole improved a broad spectrum of symptoms across the YMRS scale.

Antagonism of soluble guanylyl cyclase attenuates cutaneous vasodilation during whole body heat stress and local warming in humans.

We hypothesized that nitric oxide activation of soluble guanylyl cyclase (sGC) participates in cutaneous vasodilation during whole body heat stress and local skin warming. We examined the effects of the sGC inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), on reflex skin blood flow responses to whole body heat stress and on nonreflex responses to increased local skin temperature. Blood flow was monitored by laser-Doppler flowmetry, and blood pressure by Finapres to calculate cutaneous vascular conductance (CVC). Intradermal microdialysis was used to treat one site with 1 mM ODQ in 2% DMSO and Ringer, a second site with 2% DMSO in Ringer, and a third site received Ringer. In protocol 1, after a period of normothermia, whole body heat stress was induced. In protocol 2, local heating units warmed local skin temperature from 34 to 41°C to cause local vasodilation. In protocol 1, in normothermia, CVC did not differ among sites [ODQ, 15 ± 3% maximum CVC (CVC(max)); DMSO, 14 ± 3% CVC(max); Ringer, 17 ± 6% CVC(max); P > 0.05]. During heat stress, ODQ attenuated CVC increases (ODQ, 54 ± 4% CVC(max); DMSO, 64 ± 4% CVC(max); Ringer, 63 ± 4% CVC(max); P < 0.05, ODQ vs. DMSO or Ringer). In protocol 2, at 34°C local temperature, CVC did not differ among sites (ODQ, 17 ± 2% CVC(max); DMSO, 18 ± 4% CVC(max); Ringer, 18 ± 3% CVC(max); P > 0.05). ODQ attenuated CVC increases at 41°C local temperature (ODQ, 54 ± 5% CVC(max); DMSO, 86 ± 4% CVC(max); Ringer, 90 ± 2% CVC(max); P < 0.05 ODQ vs. DMSO or Ringer). sGC participates in neurogenic active vasodilation during heat stress and in the local response to direct skin warming.

VIP/PACAP receptor mediation of cutaneous active vasodilation during heat stress in humans.

Vasoactive intestinal peptide (VIP) is implicated in cutaneous active vasodilation in humans. VIP and the closely related pituitary adenylate cyclase activating peptide (PACAP) act through several receptor types: VIP through VPAC1 and VPAC2 receptors and PACAP through VPAC1, VPAC2, and PAC1 receptors. We examined participation of VPAC2 and/or PAC1 receptors in cutaneous vasodilation during heat stress by testing the effects of their specific blockade with PACAP6-38. PACAP6-38 dissolved in Ringer's was administered by intradermal microdialysis at one forearm site while a control site received Ringer's solution. Skin blood flow was monitored by laser-Doppler flowmetry (LDF). Blood pressure was monitored noninvasively and cutaneous vascular conductance (CVC) calculated. A 5- to 10-min baseline period was followed by approximately 70 min of PACAP6-38 (100 microM) perfusion at one site in normothermia and a 3-min period of body cooling. Whole body heating was then performed to engage cutaneous active vasodilation and was maintained until CVC had plateaued at an elevated level at all sites for 5-10 min. Finally, 58 mM sodium nitroprusside was perfused through both microdialysis sites to effect maximal vasodilation. No CVC differences were found between control and PACAP6-38-treated sites during normothermia (19 +/- 3%max untreated vs. 20 +/- 3%max, PACAP6-38 treated; P > 0.05 between sites) or cold stress (11 +/- 2%max untreated vs. 10 +/- 2%max, PACAP6-38 treated, P > 0.05 between sites). PACAP6-38 attenuated the increase in CVC during whole body heating when compared with untreated sites (59 +/- 3%max untreated vs. 46 +/- 3%max, PACAP6-38 treated, P < 0.05). We conclude that VPAC2 and/or PAC1 receptor activation is involved in cutaneous active vasodilation in humans.

Roles of nitric oxide synthase isoforms in cutaneous vasodilation induced by local warming of the skin and whole body heat stress in humans.

Nitric oxide (NO) participates in the cutaneous vasodilation caused by increased local skin temperature (Tloc) and whole body heat stress in humans. In forearm skin, endothelial NO synthase (eNOS) participates in vasodilation due to elevated Tloc and neuronal NO synthase (nNOS) participates in vasodilation due to heat stress. To explore the relative roles and interactions of these isoforms, we examined the effects of a relatively specific eNOS inhibitor, N(omega)-amino-l-arginine (LNAA), and a specific nNOS inhibitor, N(omega)-propyl-l-arginine (NPLA), both separately and in combination, on skin blood flow (SkBF) responses to increased Tloc and heat stress in two protocols. In each protocol, SkBF was monitored by laser-Doppler flowmetry (LDF) and mean arterial pressure (MAP) by Finapres. Cutaneous vascular conductance (CVC) was calculated (CVC = LDF/MAP). Intradermal microdialysis was used to treat one site with 5 mM LNAA, another with 5 mM NPLA, a third with combined 5 mM LNAA and 5 mM NPLA (Mix), and a fourth site with Ringer only. In protocol 1, Tloc was controlled with combined LDF/local heating units. Tloc was increased from 34 degrees C to 41.5 degrees C to cause local vasodilation. In protocol 2, after a period of normothermia, whole body heat stress was induced (water-perfused suits). At the end of each protocol, all sites were perfused with 58 mM nitroprusside to effect maximal vasodilation for data normalization. In protocol 1, at Tloc = 34 degrees C, CVC did not differ between sites (P > 0.05). LNAA and Mix attenuated CVC increases at Tloc = 41.5 degrees C to similar extents (P < 0.05, LNAA or Mix vs. untreated or NPLA). In protocol 2, in normothermia, CVC did not differ between sites (P > 0.05). During heat stress, NPLA and Mix attenuated CVC increases to similar extents, but no significant attenuation occurred with LNAA (P < 0.05, NPLA or Mix vs. untreated or LNAA). In forearm skin, eNOS mediates the vasodilator response to increased Tloc and nNOS mediates the vasodilator response to heat stress. The two isoforms do not appear to interact during either response.

Endothelial nitric oxide synthase control mechanisms in the cutaneous vasculature of humans in vivo.

Nitric oxide (NO) participates in locally mediated vasodilation induced by increased local skin temperature (T(loc)) and in sympathetically mediated vasodilation during whole body heat stress. We hypothesized that endothelial NOS (eNOS) participates in the former, but not the latter, response. We tested this hypothesis by examining the effects of the eNOS antagonist N(G)-amino-l-arginine (l-NAA) on skin blood flow (SkBF) responses to increased T(loc) and whole body heat stress. Microdialysis probes were inserted into forearm skin for drug delivery. One microdialysis site was perfused with l-NAA in Ringer solution and a second site with Ringer solution alone. SkBF [laser-Doppler flowmetry (LDF)] and blood pressure [mean arterial pressure (MAP)] were monitored, and cutaneous vascular conductance (CVC) was calculated (CVC = LDF / MAP). In protocol 1, T(loc) was controlled with LDF/local heating units. T(loc) initially was held at 34 degrees C and then increased to 41.5 degrees C. In protocol 2, after a normothermic period, whole body heat stress was induced (water-perfused suits). At the end of both protocols, 58 mM sodium nitroprusside was perfused at both microdialysis sites to cause maximal vasodilation for data normalization. In protocol 1, CVC at 34 degrees C T(loc) did not differ between l-NAA-treated and untreated sites (P > 0.05). Local skin warming to 41.5 degrees C T(loc) increased CVC at both sites. This response was attenuated at l-NAA-treated sites (P < 0.05). In protocol 2, during normothermia, CVC did not differ between l-NAA-treated and untreated sites (P > 0.05). During heat stress, CVC rose to similar levels at l-NAA-treated and untreated sites (P > 0.05). We conclude that eNOS is predominantly responsible for NO generation in skin during responses to increased T(loc), but not during reflex responses to whole body heat stress.

Neuronal nitric oxide synthase control mechanisms in the cutaneous vasculature of humans in vivo.

The physiological roles of constitutively expressed nitric oxide synthase (NOS) isoforms in humans, in vivo, are unknown. Cutaneous vasodilatation during both central nervous system-mediated, thermoregulatory reflex responses to whole-body heat stress and during peripheral axon reflex-mediated, local responses to skin warming in humans depend on nitric oxide (NO) generation by constitutively expressed NOS of uncertain isoform. We hypothesized that neuronal NOS (nNOS, NOS I) effects cutaneous vasodilatation during whole-body heat stress, but not during local skin warming. We examined the effects of the nNOS inhibitor 7-nitroindazole (7-NI) administered by intradermal microdialysis on vasodilatation induced by whole-body heat stress or local skin warming. Skin blood flow (SkBF) was monitored by laser-Doppler flowmetry (LDF). Blood pressure (MAP) was monitored and cutaneous vascular conductance calculated (CVC = LDF/MAP). In protocol 1, whole-body heat stress was induced with water-perfused suits. In protocol 2, local skin warming was induced through local warming units at LDF sites. At the end of each protocol, 56 mm sodium nitroprusside was perfused at microdialysis sites to raise SkBF to maximal levels for data normalization. 7-NI significantly attenuated CVC increases during whole-body heat stress (P < 0.05), but had no effect on CVC increases induced by local skin warming (P > 0.05). These diametrically opposite effects of 7-NI on two NO-dependent processes verify selective nNOS antagonism, thus proving that the nNOS isoform affects NO increases and hence vasodilatation during centrally mediated, reflex responses to whole-body heat stress, but not during locally mediated, axon reflex responses to local skin warming. We conclude that the constitutively expressed nNOS isoform has distinct physiological roles in cardiovascular control mechanisms in humans, in vivo.