Assessment of oral midazolam limited sampling strategies to predict area under the concentration time curve (AUC) during cytochrome P450 (CYP) 3A baseline, inhibition and induction or activation.

UNLABELLED: A previous study reported a 2- and 3-timepoint limited sampling strategy (LSS) model accurately predicted oral midazolam area under the concentration time curve (AUC), and thus cytochrome P450 (CYP) 3A activity. OBJECTIVE: This study evaluated whether the LSS models predict midazolam AUC during CYP3A baseline, inhibition and induction/activation. MATERIALS AND METHODS: Plasma midazolam concentrations from 106 healthy adults from 6 published studies were obtained where oral midazolam was co-administered alone or with ketoconazole, double-strength grapefruit juice, Ginkgo biloba extract, pleconaril, or rifampin. Observed and predicted midazolam AUCs were determined. Bias and precision of the LSS models were determined. RESULTS: Contrasting results were observed for the 2- and 3-timepoint LSS models in accurately predicting midazolam AUC during baseline CYP3A conditions. With the exception of 1 study (single dose, double-strength grapefruit juice), the 2- and 3-timepoint LSS models did not accurately predict midazolam AUC during conditions of CYP3A inhibition and induction/activation. CONCLUSION: The previously reported 2- and 3-timepoint oral midazolam LSS models are not applicable to the evaluated conditions of CYP3A baseline, inhibition, and induction/ activation.

Transgenic avian-derived recombinant human interferon-alpha2b (AVI-005) in healthy subjects: an open-label, single-dose, controlled study.

BACKGROUND/AIMS: This study characterized the safety and pharmacological properties of AVI-005, a novel glycosylated recombinant human interferon-alpha2b produced from the egg whites of chickens transfected with human cDNA. METHODS: 18 healthy volunteers received single subcutaneous rising doses (0.5, 1.66 or 5 million international units, MIU) of AVI-005. A randomized parallel comparator group of 10 subjects received 5 MIU of unglycosylated IFN-alpha2b (Intron A). The pharmacokinetic parameters t1/2, tmax, Cmax, AUC0-24h, Vd, and clearance were compared between AVI-005 and unglycosylated IFN-alpa2b. RESULTS: At equipotent doses, AVI-005 had a larger AUC0-24h than the control interferon. Pharmacodynamic markers ofneopterin and beta2-microglobulin for the two treatments were similar. These markers were increased by AVI-005 in a dose-dependent manner. Pharmacodynamic responses to treatment with AVI-005 were shown by the change in mRNA expression for interferon inducible protein kinase and 2'5'-oligoadenylate synthetase. Adverse events in the two groups were qualitatively and quantitatively similar. CONCLUSION: AVI-005 demonstrates biological activity and pharmaco-kinetic properties in humans that support further development.

Effect of chronic resistive loading on ventilatory control in a rat model.

Acute resistive loading of the airway has been shown to activate the endogenous opioid system, with subsequent depression of ventilation. The present investigation was designed to assess the effect of chronic airway loading on ventilation and CO2 sensitivity, and to determine whether the endogenous opioid system contributes to long-term modulation of ventilatory control in this setting. A flow-resistive ventilatory load was imposed in 2-mo-old rats by surgical implantation of a circumferential tracheal band that approximately tripled tracheal resistance. Respiration and CO2 sensitivity were serially and noninvasively assessed by barometric plethysmography over a period of 21 wk. Ventilatory output was assessed as minute inspiratory effort, which was defined as the product of plethysmograph signal amplitude, inspiratory time, and respiratory rate (RR). CO2 sensitivity was calculated as the percent change in minute inspiratory effort from room air to CO2 exposure. The effect of naloxone administration on these parameters was also determine. Arterial blood gases demonstrated hypercapnia with maintenance of normoxia in loaded rats; these findings persisted for the duration of the study. Two days after surgery, rats with tracheal obstruction demonstrated a lower RR than controls during room air breathing and during CO2 stimulation. CO2 sensitivity was significantly depressed in obstructed animals at this time. Escape from suppression of RR and CO2 sensitivity was evident by 14 to 21 d after obstruction; however, suppression of these parameters reappeared and was maintained from 56 to 147 d after obstruction. Naloxone augmented minute inspiratory effort during CO2 stimulation at 2 d after obstruction but not thereafter; naloxone had no effect in control rats. These data indicate that chronic airway loading suppresses RR and CO2 sensitivity in a triphasic manner. The early suppression is partially reversible by naloxone; late-appearing suppression is unaffected by naloxone and is presumably mediated by mechanisms that do not involve endogenous opioids.

In-vitro metabolism of celecoxib, a cyclooxygenase-2 inhibitor, by allelic variant forms of human liver microsomal cytochrome P450 2C9: correlation with CYP2C9 genotype and in-vivo pharmacokinetics.

In-vitro studies were conducted to assess the impact of CYP2C9 genotype on the metabolism (methyl hydroxylation) and pharmacokinetics of celecoxib, a novel cyclooxygenase-2 inhibitor and CYP2C9 substrate. When compared to cDNA-expressed wild-type CYP2C9 (CYP2C9*1), the Vmax/Km ratio for celecoxib methyl hydroxylation was reduced by 34% and 90% in the presence of recombinant CYP2C9*2 and CYP2C9*3, respectively. These data indicated that the amino acid substitution at position 359 (Ile to Leu) elicited a more pronounced effect on the metabolism of celecoxib than did a substitution at position 144 (Arg to Cys). The Vmax/Km ratio was also decreased in microsomes of livers genotyped CYP2C9*1/*2 (47% decrease, mean of two livers), or CYP2C9*1/*3 (59% decrease, one liver). In all cases, these changes were largely reflective of a decrease in Vmax, with a minimal change in Km. Based on simulations of the in-vitro data obtained with the recombinant CYP2C9 proteins, it was anticipated that the pharmacokinetics of celecoxib (as a much as a five-fold increase in plasma AUC) would be altered (versus CYP2C9*1/*1 subjects) in subjects genotyped heterozygous or homozygous for the CYP2C9*2 (Cys144) or CYP2C9*3 (Leu359) allele. In a subsequent clinical study, the AUC of celecoxib was increased (versus CYP2C9*1/*1 subjects) approximately 2.2-fold (range, 1.6-3-fold) in two CYP2C9*1/*3 subjects and one CYP2C9*3/*3 subject receiving a single oral dose (200 mg) of the drug. In contrast, there was no significant change in celecoxib AUC in two subjects genotyped CYP2C9*1/*2.

Differing effects of the anxiolytic agents buspirone and diazepam on control of breathing.

We compared ventilatory effects of the nonsedating anxiolytic buspirone with those of the sedating anxiolytic diazepam in nine normal men. Resting ventilatory parameters and ventilatory responses to CO2 rebreathing and inspiratory threshold loading were measured before and after placebo, diazepam, and buspirone. Placebo had no ventilatory effects. Diazepam had no effect on resting ventilation but depressed response to CO2. Buspirone had no effect on resting ventilation or CO2 response. During loading, buspirone did not alter the augmentation of mouth pressure; diazepam produced a trend toward less augmentation. Both anxiolytics altered the load compensation response for the group; in particular, an increase in ventilation during loading (seen in three of nine subjects) was suppressed by drug administration. Diazepam also markedly depressed one subject's loaded ventilation below unloaded ventilation. In summary, buspirone did not cause the depression of respiratory center chemosensitivity that was seen with diazepam and produced less depression of load compensation in normal subjects. This suggests that it may be a safer anxiolytic in patients with lung disease.

Comparison of methods for identifying early methotrexate-induced hepatotoxicity in patients with rheumatoid arthritis.

Hepatotoxicity may complicate therapy with methotrexate in patients with rheumatoid arthritis. Prevention of cirrhosis may depend upon early identification of liver damage, usually accomplished by serial biopsy. To determine the adequacy of noninvasive methods for identifying hepatotoxicity, 22 sets of data were obtained in patients undergoing therapy with methotrexate for rheumatoid arthritis. Comparisons were made between liver biopsy, hepatocellular enzymes and two noninvasive radioisotopic methods that have been shown to be abnormal in hepatocellular disease: the rate constant of excretion of the 14C-aminopyrine and the time from injection to peak hepatic activity of 99mTc-diisopropylimidodiacetic acid. The hepatocellular enzymes and the time-to-peak-activity of diisopropylimidodiacetic acid were not useful predictors of methotrexate-induced hepatotoxicity. The aminopyrine breath test was abnormal in approximately half the patients with hepatotoxicity but showed poor specificity. Noninvasive methods remain inferior to biopsy for the detection of mild to moderate methotrexate-induced hepatotoxicity in patients with rheumatoid arthritis.

Comparison of methods for calculating glomerular filtration rate: technetium-99m-DTPA scintigraphic analysis, protein-free and whole-plasma clearance of technetium-99m-DTPA and iodine-125-iothalamate clearance.

True glomerular filtration rate (GFR) was measured in normal volunteers and in patients with normal and impaired renal function by the iothalamate clearance (IC) method of Sigman. Within 24 hr, GFR was also determined by two other methods: technetium-99m- (99mTc) DTPA scintigraphic analysis (SA) utilizing a modification of the Gates computer program, and by measuring disappearance of 99mTc-DTPA from whole plasma (WPC) and from protein-free ultrafiltered plasma (PFPC). Determinations of GFR by IC and by PFPC methods were virtually identical (mean absolute error 5.36 ml/min, r = 0.99, p greater than 0.05). GFRs measured in protein-free, ultrafiltered plasma differed significantly from those obtained from whole plasma only in sicker patients and in those taking multiple medications (in whom alterations in protein-binding of DTPA may be seen). The SA method correlated less well with the iodine-125-(125I) IC method than did either the protein-free or whole-plasma clearance methods (mean absolute error 32.36 ml/min, r = 0.74, p less than 0.05). However, the SA method provided useful information with respect to differential (split) renal function.

Sleep quality in Lyme disease.

Complaints of chronic fatigue as well as sleep disturbances are prevalent in Lyme disease. We compared polysomnographic measures of sleep in patients with documented Lyme disease with those of a group of age-matched normal control subjects. Eleven patients meeting Centers for Disease Control criteria for late Lyme disease with serologic confirmation by enzyme-linked immunosorbent assay and Western blot without a history of other medical or psychiatric illness and 10 age-matched control subjects were studied. Lyme disease patients and controls underwent 2 nights of polysomnography. Multiple sleep latency testing (MSLT) was performed in the patients. Sleep was staged by standard criteria, and continuity of sleep was assessed for each stage of frequency analysis of consecutive epochs. All patients studied reported sleep-related complaints, including difficulty initiating sleep (27%), frequent nocturnal awakenings (27%), excessive daytime somnolence (73%) and restless legs/nocturnal leg jerking (9%). Greater sleep latency, decreased sleep efficiency and a greater arousal index were noted in Lyme patients. The median length of uninterrupted occurrences of stage 2 and stage 4 non-rapid eye movement (NREM) sleep was less in Lyme patients (6.3 +/- 3.0 epochs in patients vs. 11.4 +/- 4.4 epochs in controls for stage 2, p < 0.01, and 4.3 +/- 4.4 epochs in patients vs. 11.2 +/- 6.3 epochs in controls for stage 4, p < 0.01), indicating greater sleep fragmentation. Mean sleep onset latency during the MSLT was normal (12.7 +/- 5.6 minutes). Three patients demonstrated alpha-wave intrusion into NREM sleep. These sleep abnormalities may contribute to the fatigue and sleep complaints common in this disease.

Chronic intermittent hypoxia increases sympathetic responsiveness to hypoxia and hypercapnia.

We sought to determine whether chronic exposure to intermittent hypoxia (CIH) increases sympathetic responsiveness to subsequent chemoreflex stimulation. Sprague-Dawley rats were exposed to 30 days of CIH: exposure chamber %O2 [fractional concentration of chamber O2 (FcO2)] nadir 6.5-7% with return to 21% each minute for 8 h/day during the diurnal sleep period (Exp group). Sham controls (SC group) were similarly handled but kept at 21% FcO2 and compared with unhandled controls (UC group). Rats were then anesthetized with urethan, and preganglionic cervical sympathetic activity (CSA), diaphragm electromyogram, arterial pressure, and electrocardiogram were recorded while the rats were spontaneously breathing 100% O2, room air, 10% O2, 12% CO2, and 10% O2-12% CO2. CSA and heart rate were also recorded during phenylephrine infusion to assess baroreceptor function. Mean arterial pressure was significantly greater in Exp than in SC and UC rats during all conditions (P < 0. 05). A vasopressor response to 10% O2-12% CO2 was observed only in Exp rats. CSA was greater in Exp than in SC and UC rats during 10% O2, 12% CO2, and 10% O2-12% CO2 but not during room-air exposure. A significant increase in CSA compared with room air was noted during 10% O2, 12% CO2, and 10% O2-12% CO2 in Exp but not in SC or UC rats. No differences in baroreceptor function were observed among groups. We conclude that CIH leads to increased sympathetic responsiveness to chemoreflex stimulation.

Background ventilatory stimulus as a determinant of load compensation.

Compensation for inspiratory flow-resistive loading was compared during progressive hypercapnia and incremental exercise to determine the effect of changing the background ventilatory stimulus and to assess the influence of the interindividual variability of the unloaded CO2 response on evaluation of load compensation in normal subjects. During progressive hypercapnia, ventilatory response was incompletely defended with loading (mean unloaded delta VE/delta PCO2 = 3.02 +/- 2.29, loaded = 1.60 +/- 0.67 1.min-1.Torr-1 CO2, where VE is minute ventilation and PCO2 is CO2 partial pressure; P less than 0.01). Furthermore the degree of defense of ventilation with loading was inversely correlated with the magnitude of the unloaded CO2 response. During exercise, loading produced no depression in ventilatory response (mean delta VE/delta VCO2 unloaded = 20.5 +/- 1.9, loaded = 19.2 +/- 2.5 l.min-1.l-1.min-1 CO2 where VCO is CO2 production; P = NS), and no relationship was demonstrated between degree of defense of the exercise ventilatory response and the unloaded CO2 response. Differences in load compensation during CO2 rebreathing and exercise suggest the presence of independent ventilatory control mechanisms in these states. The type of background ventilatory stimulus should therefore be considered in load compensation assessment.

Effect of chronic resistive loading on hypoxic ventilatory responsiveness.

Depression of ventilation mediated by endogenous opioids has been observed acutely after resistive airway loading. We evaluated the effects of chronically increased airway resistance on hypoxic ventilatory responsiveness shortly after load imposition and 6 wk later. A circumferential tracheal band was placed in 200-g rats, tripling tracheal resistance. Sham surgery was performed in controls. Ventilation and the ventilatory response to hypoxia were measured by using barometric plethysmography at 2 days and 6 wk postsurgery in unanesthetized rats during exposure to room air and to 12% O2-5% CO2-balance N2. Trials were performed with and without naloxone (1 mg/kg i.p.). Room air arterial blood gases demonstrated hypercapnia with normoxia in obstructed rats at 2 days and 6 wk postsurgery. During hypoxia, a 30-Torr fall in PO2 occurred with no change in PCO2. Hypoxic ventilatory responsiveness was suppressed in obstructed rats at 2 days postloading. Naloxone partially reversed this suppression. However, hypoxic responsiveness at 6 wk was not different from control levels. Naloxone had a small effect on ventilatory pattern at this time with no overall effect on hypoxic responsiveness. This was in contrast to previously demonstrated long-term suppression of CO2 sensitivity in this model, which was partially reversible by naloxone only during the immediate period after load imposition. Endogenous opioids apparently modulate ventilatory control acutely after load imposition. Their effect wanes with time despite persistence of depressed CO2 sensitivity.

Paradoxical hypotension and bradycardia after intravenous arginine vasopressin.

Standard therapy for variceal bleeding includes endoscopic sclerotherapy and esophageal balloon tamponade. In addition, pharmacologic therapies, including arginine vasopressin (AVP), are frequently used in hemodynamically unstable patients or where sclerotherapy has been unsuccessful. A case is described herein of a 30-year-old woman with a history of ethanol abuse, hematemeisis, and biopsy-proven hepatic cirrhosis in which the addition of AVP to an antivariceal regimen of octreotide was associated with a paradoxical episode of hypotension, bradycardia, and hypoxia. Indeed, within 15 minutes after initiation of an AVP infusion, the patient exhibited hypotension with a systolic blood pressure of 80 mmHg, a relative bradycardia to 76 beats per minute, and a desaturation of blood oxygen to 84%. The AVP infusion was discontinued 2 hours later and blood pressure, heart rate, and oxygen saturation rapidly returned to baseline. This temporal correlation between the onset and termination of the physiologic effects and the initiation and discontinuation of the AVP infusion suggests a causal relationship. The paradoxical physiologic effects might reflect cardiac ischemia secondary to vasospasm and/or central suppression of the autonomic nervous system induced by AVP.

Time of peak drug concentration after a single dose and a dose at steady state.

The time of peak concentration after administration of oral drug is an often quoted and used pharmacokinetic parameter. It is not well appreciated, however, that the peak times after a single dose and a dose at steady state during a multiple administration regimen can differ significantly. This article derives the mathematical relationships that determine how a peak time at steady state differs from that after a single or first dose. These relationships are then evaluated using three different approaches: 1) graphic simulations of time courses of drug concentration for three hypothetical drugs; 2) comparisons of predicted and observed peak times using examples from the literature; and 3) comparisons of predicted and simulated peak times based on different sampling schedules for three hypothetical drugs. The key finding is that peak times after a dose at steady state can occur considerably earlier after administration than after a single dose. However, the manner by which peak times are usually determined, that is, the sampling time corresponding to the highest measured drug concentration, imposes significant limitations on the usefulness of this parameter.

A new cyclooxygenase-2 inhibitor, rofecoxib (VIOXX), did not alter the antiplatelet effects of low-dose aspirin in healthy volunteers.

The present study examined whether rofecoxib (VIOXX), a new specific inhibitor of cyclooxygenase-2 (COX-2), would interfere with the desired antiplatelet effects of aspirin. Thus, the effects of rofecoxib on inhibition of ex vivo serum-generated thromboxane B2 (TXB2) and platelet aggregation by low doses (81 mg) of aspirin were examined in healthy volunteers. This was a double-blind, randomized, placebo-controlled, parallel study of two treatment groups (n = 12 per group) in which subjects received 50 mg of rofecoxib or placebo for 10 days in a blinded fashion. Subjects also received 81 mg aspirin once on each of days 4 through 10 in an open-label fashion. Blood for measurement of serum TXB2 production and platelet aggregation studies was collected on day 1 (prior to rofecoxib/placebo), on day 4 (prior to aspirin), and on day 10 (before and 4 hours following the seventh dose of aspirin). Platelet-derived serum TXB2 (COX-1 assay) was measured in blood clotted for 1 hour at 37 degrees C. Platelet aggregation was independently induced employing 1 mM arachidonic acid and 1 microgram/mL collagen as agonists. Rofecoxib administered alone had no significant effect on serum TXB2 production or platelet aggregation (day 4). TXB2 production was inhibited 98.4% by aspirin coadministered with either rofecoxib or placebo (day 10). Similarly, platelet aggregation induced by arachidonic acid was inhibited 93.7% and 93.5% by aspirin coadministered with either rofecoxib or placebo, respectively (day 10). The comparable values for inhibition of collagen-induced platelet aggregation were 86.8% and 90.8%, respectively. No important clinical or laboratory adverse experiences were observed. In conclusion, rofecoxib alone (50 mg QD for 4 days) did not inhibit serum TXB2 production or platelet aggregation. In addition, rofecoxib (50 mg QD for 10 days) did not alter the antiplatelet effects of low-dose aspirin (inhibition of platelet aggregation and TXB2 production). Rofecoxib was generally well tolerated when administered alone or in combination with low-dose aspirin.

Antiplatelet effects of MK-852, a platelet fibrinogen receptor antagonist, in healthy volunteers.

MK-852, a cyclic heptapeptide, is a potent platelet fibrinogen receptor antagonist. When administered to normal healthy male subjects by 1- and 4-hour constant rate intravenous infusions, it provides a generally well-tolerated and reversible means of inhibition of platelet function. At infusion rates of 1 microgram/kg/min for 1 hour and 0.44 microgram/kg/min for 4 hours, respectively, MK-852 extended baseline bleeding time by greater than 2.2-fold and 2.6-fold, inhibited ADP-induced platelet aggregation by 76% and 69%, and inhibited collagen-induced platelet aggregation by 65% and 67%, respectively. The pharmacokinetics of MK-852 include an elimination half-life of approximately 2 hours, total clearance of about 150 ml/min, and volume of distribution of about 18 liters. Examination of the relationship between MK-852 whole-blood concentration in vitro and inhibition of platelet aggregation showed an EC50 of about 55 ng/ml and a Hill coefficient of 1.55. The infusions were generally well tolerated, with no study drug-related changes in blood counts or biochemical profiles.

Pharmacokinetics and safety of single intravenous infusions of the adenosine agonist, AMP 579, in patients with end-stage renal insufficiency.

The pharmacokinetics of an adenosine agonist (AMP 579) were characterized in patients with end-stage renal disease compared to sex- and age-matched healthy volunteers. All study participants were administered single AMP 579 doses of 50 micrograms/kg as a 6-hour, constant-rate intravenous infusion. Serial blood samples were obtained for measurement of plasma AMP 579 concentration, and predose samples were collected for determination of AMP 579 plasma protein binding. The safety of AMP 579 administration in renally impaired patients also was evaluated. AMP 579 was rapidly cleared from the systemic circulation in all subjects as plasma concentrations were below the limit of detection by 2 to 4 hours after terminating the infusion. Noncompartmental analysis yielded mean values for the plasma AMP 579 concentration at the end of the 6-hour infusion (C6 h) of 9.6 and 10.5 ng/mL and for systemic clearances (Cl) of 0.91 and 0.72 L/h/kg in renally impaired patients and healthy volunteers, respectively. Mean volumes of distribution (Vss) in the renally impaired and healthy volunteers were 0.92 and 0.84 L/kg, and terminal elimination half-life values (t1/2) were 1.61 and 1.33 hours, respectively. The extent to which AMP 579 is bound to plasma protein was not altered in renally impaired patients since the free fractions were 4.0% and 3.4% for renally impaired and healthy volunteers, respectively. It was concluded that the pharmacokinetic parameters of AMP 579 were similar in both groups. The 6-hour AMP 579 infusion was generally well tolerated by both renal patients and healthy volunteers. There were no serious adverse events, and there were only two mild adverse events in 1 renally impaired patient judged possibly related to the study drug that quickly resolved. There were no clinically significant changes in laboratory values or clinical evaluations during the study. There was a slight increase in heart rate during the infusion of similar magnitude for both the renal patients and healthy volunteers. These data suggest that AMP 579 may be administered to renally impaired patients with minimal cardiovascular effects and adverse events. These results in end-stage renal patients (worst-case scenario) indicate that dose adjustment in patients with renal insufficiency of any degree is not indicated in future studies of AMP 579.

Simvastatin does not affect CYP3A activity, quantified by the erythromycin breath test and oral midazolam pharmacokinetics, in healthy male subjects.

Potential for inhibition of CYP3A activity by simvastatin, an HMG-CoA reductase inhibitor, was evaluated in 12 healthy male subjects who received placebo or 80 mg of simvastatin, the maximal recommended dose, once daily for 7 consecutive days. On day 7, an intravenous injection of 3 microCi [14C N-methyl]erythromycin for the erythromycin breath test (EBT) was coadministered with a 2 mg oral solution of midazolam. The values for percent 14C exhaled during the first hour (for EBT) and the pharmacokinetic parameters of midazolam (AUC, Cmax, t1/2) were not affected following multiple once-daily oral doses of simvastatin 80 mg. The 95% confidence interval was 0.97 to 1.18 for EBT and 0.99 to 1.23 for midazolam AUC. In addition, the total urinary recoveries of midazolam and its 1'-hydroxy metabolites (free plus conjugate) obtained from both treatments were not statistically different (p > 0.200). These data demonstrate that multiple dosing of simvastatin, at the highest recommended clinical dose, does not significantly alter the in vivo hepatic or intestinal CYP3A4/5 activity as measured by the commonly used EBT and oral midazolam probes.

Chronic-intermittent hypoxia induces immediate early gene expression in the midline thalamus and epithalamus.

Chronic-intermittent hypoxia (CIH) was postulated to activate thalamic regions that are synaptically related to autonomic-related areas of the cerebral cortex. Animals exposed to CIH for 30 days exhibited c-fos labeling in paraventricular thalamic and lateral habenular nuclei. Our findings strongly suggest activation of a diencephalic network that participates in behavioral responses to chronic stress.

Immediate-early gene expression in cerebral cortex following exposure to chronic-intermittent hypoxia.

Chronic-intermittent hypoxia (CIH) was postulated to evoke c-fos expression in cortical regions that modulate sympathetic discharge. Animals exposed to CIH for 30 days exhibited c-fos labeling in medial prefrontal, cingulate, retrosplenial, and insular cortices. Our findings strongly suggest activation of cortical circuits that adaptively regulate sympathetic and cardiovascular activities.