Mihoko Kudo

The relationship between salivary biomarkers and state-trait anxiety inventory score under mental arithmetic stress: a pilot study.

Measurement of stress hormones is a common objective method for assessment of mental stress. However, the stress of blood sampling alone may also increase stress hormone levels. In the present study, we sampled salivary biomarkers from healthy volunteers under noninvasive conditions and determined their efficacy to assess mental stress. Specifically, we examined the relationship between State Anxiety Inventory score (STAI-s) in subjects exposed to arithmetic stress and salivary chromogranin-A, &agr;-amylase, or cortisol. The STAI-s was significantly correlated to salivary &agr;-amylase (r = 0.589; P < 0.01) but not to salivary chromogranin-A or cortisol. Therefore, salivary &agr;-amylase is a useful indicator of psychosocial stress.

Orexinergic neurons and barbiturate anesthesia

Orexins (OXs) regulate sleep with possible interactions with brain noradrenergic neurons. In addition, noradrenergic activity affects barbiturate anesthesia. As we have also recently reported that OXs selectively evoke norepinephrine release from rat cerebrocortical slices we hypothesized that barbiturate anesthesia may result from of an interaction with central orexinergic systems. To test this hypothesis, we performed a series of in vivo and in vitro studies in rats. In vivo, the effects of i.c.v. OX A, B and SB-334867-A (OX1 receptor antagonist) on pentobarbital, thiopental or phenobarbital-induced anesthesia times (loss of righting reflex) was assessed. In vitro effects of barbiturates and SB-334867-A on OX-evoked norepinephrine release from cerebrocortical slice was examined. In Chinese hamster ovary cells expressing human OX1/OX2 receptors OX A- and B-evoked increases in intracellular Ca2+ were measured with and without barbiturates. OX A and B significantly decreased pentobarbital, thiopental and phenobarbital anesthesia times by 15-40%. SB-334867-A increased thiopental-induced anesthesia time by approximately by 40%, and reversed the decrease produced by OX A. In vitro, all anesthetic barbiturates inhibited OX-evoked norepinephrine release with clinically relevant IC50 values. A GABAA antagonist, bicuculline, did not modify the inhibitory effects of thiopental and the GABAA agonist, muscimol, did not inhibit norepinephrine release. In addition there was no interaction of barbiturates with either OX1 or OX2 receptors. Collectively our data suggest that orexinergic neurons may be an important target for barbiturates, and GABAA, OX1 and OX2 receptors may not be involved in this interaction.

Orexin A and B evoke noradrenaline release from rat cerebrocortical slices

Orexin A and B, recently identified in the rat hypothalamus are endogenous neuropeptide agonists for the G‐protein coupled orexin‐1 (OX1) and orexin‐2 (OX2) receptors. In the present study, we have examined the effects of orexin A, B and raised extracellular K+ on noradrenaline release from the rat cerebrocortical slice. We have compared this with other sleep – wake‐related (excitatory) neurotransmitters; dopamine, glutamate, serotonin and histamine. Neurotransmitter release studies were performed in rat cerebrocortical slices incubated in modified Krebs buffer (with and without Ca2++EGTA 1 mM) with various concentrations of orexin A, B and K+ for various times. Orexin A and B‐evoked (10−7 M) noradrenaline release was time‐dependent reaching a maximum some 10 min after stimulation. K+ (40 mM) evoked release was also time dependent but reached a maximum after 6 min. Orexin A, B and K+ stimulation of release was concentration dependent with pEC50 and Emax (% of basal) values of 8.74±0.32 (1.8 nM) and 263±14% and 8.61±0.38 (2.4 nM) and 173±7% and 1.43±0.02 (37 mM) and 1430±70%, respectively. Orexin‐evoked release was partially extracellular Ca2+ dependent. Of the other transmitters studied there was a weak orexin A and B stimulation of glutamate release. In contrast K+ evoked dopamine, glutamate, histamine and serotonin release with pEC50 and Emax (% of basal) values of 1.47±0.05 (34 mM) and 3430±410%, 1.38±0.04 (42 mM) and 1240±50%, 1.47±0.02 (34 mM) and 480±10% and 1.40±0.05 (40 mM) and 560±60% respectively. We conclude that the neuropeptides orexin A and B evoke noradrenaline release from rat cerebrocortical slices.

Effects of central hypocretin-1 administration on hemodynamic responses in young-adult and middle-aged rats.

The prevalence of hypertension in middle age correlates with impaired autonomic regulation and as norepinephrinergic neurons decline with increasing age, and this reduction may contribute to this impairment. Central hypocretin-activated norepinephrinergic neurons contribute to sympathetic regulation. In the present study we compared sympathoadrenal effects of intracerebroventricular (i.c.v.) hypocretin-1(5 nmol) between young-adult (12-14 weeks) and middle-aged (12-14 months) rats. Arterial blood pressure, heart rate and plasma catecholamines were assessed under pentobarbital anesthesia. In addition, we compared hypocretin-1 and K(+)-evoked norepinephrine release from the cerebrocortical slices prepared from young-adult and middle-aged rats. We also examined whether the novel hypocretin receptor-1 antagonist (SB-334867) could reverse these hypocretin-1 effects both in vivo and in vitro. I.c.v. hypocretin-1 significantly increased blood pressure by some 7%, heart rate by 9% and plasma norepinephrine concentrations by 100% in young-adult rats. In middle-aged rats these parameters did not change. Plasma epinephrine did not increase in either group. There was a significant correlation between changes in mean arterial pressure and plasma norepinephrine. Similarly, hypocretin-1 evoked norepinephrine release from cerebrocortical slices prepared from young-adult rats was significantly higher than that of middle-aged rats whilst K(+)-evoked release did not differ between the groups. SB-334867 significantly attenuated hypocretin-1-increased blood pressure and both in vivo and in vitro norepinephrine release. The present data suggest that hypocretinergic neurons may contribute to the regulation of central but not adrenal sympathetic activity. Moreover, sympathetic regulation by hypocretinergic neurones may disappear in middle-age in rats.

Effects of general anaesthesia and surgery on renal function and plasma adh levels

SummaryPlasma levels of antidiuretic hormone (ADH) were evaluated in 40 adult patients during and after various types of anaesthesia and surgery. The plasma level of ADH increased significantly 30 minutes after the start of anaesthesia with diethyl-ether (3.7 times) and after thiopentone (1.5 times), but it increased insignificantly in neuroleptanaesthesia (2.4 times) and with halothane (1.3 times). The surgical stress evoked marked increases in plasma ADH levels especially at ten minutes after the skin incision. A slight increase in plasma ADH level still continued into the early post-operative days.The effects of halothane anaesthesia on plasma levels of ADH and on both cortical and medullary renal blood flow (RBF) were investigated in dogs. RBF was measured by means of a heated thermocouple in two groups of eight dogs each. One group was given a high fluid load of 30 ml/kg/hr and the other a low load of 10 ml/kg/hr. The plasma level of ADH increased significantly with deepening halothane anaesthesia in the low fluid load group. However, in the high fluid load dogs it remained unchanged in spite of an increasing inspired halothane concentration. Both cortical and medullary RBF fell significantly as compared with the control values in the low fluid load group. However, in the high fluid load dogs no significant decrease was observed. These results would indicate that the anaesthetic agents investigated in the present study caused increases in plasma ADH levels, but that these antidiuretic effects of anaesthesia might be modified by the volume of fluid infused during anaesthesia and operation.RésuméPendant et après la chirurgie sous différents agents anesthésiques, on a déterminé la concentration plasmatique de ľhormone antidiurétique (ADH) chez 40 patients adultes opérés pour des pathologies abdominales variées. Une augmentation significative de ľADH a été notée après 30 minutes ďanesthésie à ľéther diéthylique (3.7 fois le contrôle) et le thiopentone (1.5 fois). Cette augmentation n’a pas été jugée significative après la neuroleptanesthésie (2.4 fois) et ľanesthésie à ľhalothane (1.3 fois). Le stress chirurgical a provoqué une augmentation importante, surtout à ta dixième minute après ľincision. Le niveau sanguin est demeuré légèrement élevé dans la période post-opératoire immédiate.Les effets de ľanesthésie à ľhalothane sur la concentration plasmatique de ľADH et sur le flux sanguin rénal cortical et médullaire ont aussi fait ľobjet ďune étude chez le chien. Dans deux groupes de huit chiens, on a mesuré au thermocouple le flux sanguin rénal. Le premier groupe a reçu une surcharge liquidienne de 30 ml/kg/hre alors que ľapport n’a été que de 10 ml/kg/hre pour le deuxième groupe. La concentration plasmatique ďADH s’est élevée de façon significative dans le deuxième groupe. Toutefois, dans le premier groupe qui avait reçu le plus grand volume liquidien, le niveau plasmatique ďADH n’a pas changé malgré les augmentations de concentration de ľhalothane. Dans le groupe où ľapport liquidien a été le moins élevé, le flux sanguin cortical et le flux médullaire ont diminué de façon significative par comparaison aux valeurs de contrôle de ce groupe. Cette diminution n’a pas été notée pour le groupe surchargé. Ces résultats suggèrent que les agents anesthésiques utilisés dans cette étude augmentent le niveau ďADH, mais que les effets antidiurétiques de ľanesthésie peuvent ïtre modifiés par la quantité de liquide perfusée pendant ľanesthésie et ľopération.

Orexin A decreases ketamine-induced anesthesia time in the rat: the relevance to brain noradrenergic neuronal activity.

BACKGROUND: Orexins (OXs) regulate wakefulness, and a lack of OX Type-I receptors cause narcolepsy. OX selectively increases norepinephrine (NE) release from rat cerebral cortical slices, and brain noradrenergic neurons are involved in the sleep-wakefulness cycle. Ketamine increases NE release from the rat cerebral cortex. We hypothesized that OX would affect ketamine anesthesia’s interactions with brain noradrenergic neuronal activity. METHODS: We used Sprague Dawley rats. We studied 1) in vivo effects of orexin A (OXA) and SB-334867-A (Orexin-1 receptor antagonist) on ketamine-induced anesthesia time, 2) in vivo effects of OXA on ketamine-induced increase in NE release from the frontal cortex assessed using microdialysis, and 3) in vitro effects of ketamine on OXA-evoked NE release from rat cerebrocortical slices. RESULTS: 1) Intracerebroventricular OXA 1 nmol significantly decreased ketamine anesthesia time by 20%–30% at 50, 100, and 125 mg/kg intraperitoneal (IP) ketamine. SB-334867-A fully reversed the decrease produced by OXA. 2) OXA also decreased the release of NE induced by ketamine even though OXA increased the release of NE in rat prefrontal cortex. Maximum NE release in Group OX + K (intracerebroventricular OXA 1 nmol + IP ketamine 100 mg/kg) was 271% and was significantly smaller than that in Group K (ketamine 100 mg/kg IP, 390% of baseline, P = 0.029). 3) Ketamine inhibited OX-evoked NE release with clinically relevant IC50 values. CONCLUSION: Orexinergic neurons may be an important target for ketamine. OXA antagonized ketamine anesthesia via Orexin-1 receptor with noradrenergic neurons.

Role of coerulean noradrenergic neurones in general anaesthesia in rats

BACKGROUND Central noradrenergic neurones have a role in alertness, analgesia, and thermoregulation; these neurones are also involved in the mechanism of anaesthesia. Locus coeruleus neurones innervate various central nervous regions including the cerebral cortex and hippocampus, and are responsible for wakefulness and analgesia. We hypothesized that these neurones are also involved in both activation of the γ-aminobutyric acid type A (GABA(A)) receptor and inhibition of N-methyl-d-aspartate (NMDA) receptor-mediated anaesthesia. METHODS Forty-seven male rats were used to compare duration of anaesthesia before and 10 days after noradrenergic neurone depletion after intraperitoneal (i.p.) administration of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4; 0, 5, and 50 mg kg(-1)). The animals received i.p. thiopental (GABA anaesthetic, 45 mg kg(-1)) or ketamine (NMDA anaesthetic, 100 mg kg(-1)). We also tested the effects of coerulean noradrenergic neurone depletion on i.p. ketamine analgesia (15 mg kg(-1)) using the hot-plate test in a further 21 male rats. At the end of each experiment, norepinephrine contents in the cerebral cortex and hippocampus were measured. RESULTS I.P. DSP-4 5 and 50 mg kg(-1) significantly decreased ketamine anaesthesia duration by 12.7% and 22.4%, increased thiopental anaesthesia duration by 10.8% and 24.5%, and reduced ketamine-increased hot-plate latency by 55.2% and 68.1%, respectively. In addition, i.p. DSP-4 5 and 50 mg kg(-1) significantly reduced norepinephrine contents in coerulean brain regions by ∼20% and ∼75%, respectively. There were significant correlations between norepinephrine contents in coerulean brain regions and anaesthesia durations and ketamine analgesia. CONCLUSIONS The present data indicate that coerulean noradrenergic neurones may be responsible for both GABA- and NMDA-mediated anaesthetic actions.

Isoflurane increases norepinephrine release in the rat preoptic area and the posterior hypothalamus in vivo and in vitro: Relevance to thermoregulation during anesthesia

General anesthetics modulate autonomic nervous system function including thermoregulatory control, which resides in the preoptic area of the anterior hypothalamus. However, the mechanism by which anesthetics modulate hypothalamic function remains unknown. We hypothesized that isoflurane increases norepinephrine release in the preoptic area and in the posterior hypothalamus causing hypothermia during anesthesia. To test this hypothesis, we performed a series of in vivo and in vitro studies in rats. In vivo studies: 1) Norepinephrine release was measured by microdialysis in the preoptic area or the posterior hypothalamus (n=9 each) before, during (30 min), and after (50 min) rats were anesthetized with 2% isoflurane. 2) In five rats, blood gases and arterial pressure were measured. 3) Body temperature changes (n=6 each) were measured after prazosin (0, 0.05, 0.5 microg), norepinephrine (0, 0.1, 1.0 microg), or 0.5 microg prazosin with 1.0 microg norepinephrine injection into the preoptic area. In vitro study: Norepinephrine release was measured from anterior or posterior hypothalamic slices (n=10 each) incubated with 0, 1, 2, or 4% isoflurane in Ca2+-containing buffer or with 4% isoflurane (n=10) in Ca2+-free buffer. Data were analyzed with repeated measures or factorial ANOVA and Student-Newman-Keuls tests. P<0.05 was significant. During anesthesia, norepinephrine release in the preoptic area was increased approximately 270%, whereas the release in the posterior hypothalamus remained unchanged. During emergence, posterior hypothalamic norepinephrine release increased by approximately 250% (P<0.05). Rectal temperature changes correlated with norepinephrine release from the preoptic area. Norepinephrine in the preoptic area enhanced isoflurane-induced hypothermia, while prazosin reversed it. Norepinephrine release from anterior hypothalamic slices increased at all isoflurane concentrations, but only at the highest concentration in posterior hypothalamic slices. Under Ca2+-free conditions, 4% isoflurane increased norepinephrine from both regions. These results suggest that augmentation of norepinephrine release in the preoptic area is responsible for hypothermia during general anesthesia.

Antinociceptive effects of neurotropin in a rat model of central neuropathic pain: DSP-4 induced noradrenergic lesion

Neurotropin is a nonprotein extract isolated from inflamed skin of rabbits inoculated with vaccinia virus, and used for treatment of neuropathic pain. In the present study, we have determined whether neurotropin could exert antinociceptive action using the central neuropathic pain model that we recently established. Rats were randomly allocated to 3 groups: Sham group (n=20), DSP-4 [N-(-2-chloroethyl)-N-ethyl-2-bromobenzylamine] group (50mg/kg ip, n=18), and DSP-4+5,7-DHT [5,7-dihydroxytryptamine] group (ip DSP-4 50mg/kg+icv 5,7-DHT 200μg, n=18). In Sham, DSP-4 and DSP-4+5,7-DHT groups, the effects of ip neurotropin (100NU/Kg) on hot-plate latency in rats with no lesion, noradrenergic neuron depletion and both noradrenergic and serotonergic neuronal depletion were studied, respectively. Rats in each group were subdivided equally to 2 subgroups: saline and neurotropin. After completion of the hot-plate tests, each rat was decapitated, the cerebral cortex was dissected from its internal structure for measurement of norepinephrine contents. Hot-plate latency significantly decreased by ∼40% 10 days after ip DSP-4 or after ip DSP-4 and 5,7-DHT. Norepinephrine contents in DSP-4 treated rats (55.6±6.3ng/ng tissue) and DSP-4+5,7-DHT treated rats (35.3±6.3ng/ng tissue) were significantly lower than those in intact rats (131.6±5.7ng/ng tissue, p<0.01). Neurotropin significantly increased the area under the curve (AUC) of the hot-plate latency in the DSP-4 and DSP-4+5,7-DHT groups but not in the Sham group. There was a significant correlation between AUC and norepinephrine contents in saline subgroup (p<0.01, r=0.597) but not in neurotropin subgroup in DSP-4 group. Neurotropin exerted an antinociceptive effect in DSP-4 induced central neuropathic pain. The present data suggest neuronal pathways other than descending inhibitory noradrenergic and serotonergic systems may be involved in neurotropin mediated antinociception.

Brief reports: plasma ropivacaine concentrations after ultrasound-guided rectus sheath block in patients undergoing lower abdominal surgery.

A rectus sheath block can provide postoperative analgesia for midline incisions. However, information regarding the pharmacokinetics of local anesthetics used in this block is lacking. In this study, we detail the time course of ropivacaine concentrations after this block. Thirty-nine patients undergoing elective lower abdominal surgery were assigned to 3 groups receiving rectus sheath block with 20 mL of different concentrations of ropivacaine. Peak plasma concentrations were dose dependent, and there were no significant differences in the times to peak plasma concentrations. The present data also suggested a slower absorption kinetics profile for ropivacaine after rectus sheath block than other compartment blocks.