Regulation of regional cerebral blood flow by cholinergic fibers originating in the basal forebrain

Ninjin'yoeito Modulates Baseline and Reperfusion-Induced Changes in the Arteriole Diameter and Blood Flow in the Cerebral Cortex of Anesthetized Mice

OBJECTIVE

Intragastric administration of ninjin'yoeito (NYT), a traditional Japanese herbal medicine, reportedly prevents the decrease in baseline cerebral blood flow (CBF) in the cortex following gastric administration of water. We investigated the effect of NYT on baseline and dynamic changes in cerebral cortical arteriole diameter.

METHODS

Urethane-anesthetized mice were intragastrically administered 1 g/kg NYT or distilled water (DW). The artery in the left parietal cortex was imaged using two-photon microscopy. The baseline diameter of penetrating arterioles was measured before and 50-60 min after administration. Dynamic CBF and arteriole diameter changes before, during, and after transient occlusion of the left common carotid artery were measured approximately 10 min after administration.

RESULTS

DW decreased the baseline diameter of the penetrating arterioles, whereas NYT did not. During occlusion, the increase in penetrating arteriole diameter was comparable for DW and NYT; however, during reperfusion, the return to preocclusion diameter was slower for NYT than DW. Laser-speckle contrast imaging confirmed that CBF, although comparable during occlusion, was higher during reperfusion for NYT than DW.

CONCLUSIONS

These results suggest that NYT attenuates vasoconstriction in penetrating arterioles after intragastric administration and during cerebral reperfusion, contributing to CBF regulation.

Optogenetic stimulation of vagal nerves for enhanced glucose-stimulated insulin secretion and β cell proliferation

The enhancement of insulin secretion and of the proliferation of pancreatic β cells are promising therapeutic options for diabetes. Signals from the vagal nerve regulate both processes, yet the effectiveness of stimulating the nerve is unclear, owing to a lack of techniques for doing it so selectively and prolongedly. Here we report two optogenetic methods for vagal-nerve stimulation that led to enhanced glucose-stimulated insulin secretion and to β cell proliferation in mice expressing choline acetyltransferase-channelrhodopsin 2. One method involves subdiaphragmatic implantation of an optical fibre for the photostimulation of cholinergic neurons expressing a blue-light-sensitive opsin. The other method, which suppressed streptozotocin-induced hyperglycaemia in the mice, involves the selective activation of vagal fibres by placing blue-light-emitting lanthanide microparticles in the pancreatic ducts of opsin-expressing mice, followed by near-infrared illumination. The two methods show that signals from the vagal nerve, especially from nerve fibres innervating the pancreas, are sufficient to regulate insulin secretion and β cell proliferation.

Influence of age on nicotinic cholinergic regulation of blood flow in rat's olfactory bulb and neocortex

The olfactory bulb receives cholinergic basal forebrain inputs as does the neocortex. With a focus on nicotinic acetylcholine receptors (nAChRs), this review article provides an overview and discussion of the following findings: (1) the nAChRs-mediated regulation of regional blood flow in the neocortex and olfactory bulb, (2) the nAChR subtypes that mediate their responses, and (3) their activity in old rats. The activation of the α4β2-like subtype of nAChRs produces vasodilation in the neocortex, and potentiates olfactory bulb vasodilation induced by olfactory stimulation. The nAChR activity producing neocortical vasodilation was similarly maintained in 2-year-old rats as in adult rats, but was clearly reduced in 3-year-old rats. In contrast, nAChR activity in the olfactory bulb was reduced already in 2-year-old rats. Thus, age-related impairment of α4β2-like nAChR function may occur earlier in the olfactory bulb than in the neocortex. Given the findings, the vasodilation induced by α4β2-like nAChR activation may be beneficial for neuroprotection in the neocortex and the olfactory bulb.

Blood pressure pulsations modulate central neuronal activity via mechanosensitive ion channels

The transmission of the heartbeat through the cerebral vascular system causes intracranial pressure pulsations. We discovered that arterial pressure pulsations can directly modulate central neuronal activity. In a semi-intact rat brain preparation, vascular pressure pulsations elicited correlated local field oscillations in the olfactory bulb mitral cell layer. These oscillations did not require synaptic transmission but reflected baroreceptive transduction in mitral cells. This transduction was mediated by a fast excitatory mechanosensitive ion channel and modulated neuronal spiking activity. In awake animals, the heartbeat entrained the activity of a subset of olfactory bulb neurons within ~20 milliseconds. Thus, we propose that this fast, intrinsic interoceptive mechanism can modulate perception-for example, during arousal-within the olfactory bulb and possibly across various other brain areas.

Nicotinic cholinergic regulation of olfactory bulb blood flow response in aged rats

In our previous research, we had demonstrated the crucial role of neuronal nicotinic acetylcholine receptors (nAChRs) in potentiation of the olfactory bulb blood flow response to olfactory stimulation in adult rats. The present study examined the effects of nAChR activation on the olfactory bulb blood flow response in rats aged 24-27 months. We found that, under urethane anesthesia, unilateral olfactory nerve stimulation (300 μA, 20 Hz, 5 s) increased blood flow within the ipsilateral olfactory bulb, without changes in the systemic arterial pressure. The increase in blood flow was dependent upon the current and frequency of the stimulus. Intravenous administration of nicotine (30 μg/kg) had little effect on the olfactory bulb blood flow response to nerve stimulation at either 2 Hz or 20 Hz. These results suggest a reduction in nAChR-mediated potentiation of the olfactory bulb blood flow response in aged rats.

Deep brain stimulation of the nucleus basalis of Meynert in an experimental rat model of dementia: Stimulation parameters and mechanisms

BACKGROUND/OBJECTIVE

Deep brain stimulation (DBS) of the nucleus basalis of Meynert (NBM) has gained interest as a potential therapy for treatment-resistant dementia. However, optimal stimulation parameters and mechanisms of action are yet to be elucidated.

METHODS

First, we assessed NBM DBS at different stimulation parameters in a scopolamine-induced rat model of dementia. Rats were tested in the object location task with the following conditions: (i) low and high frequency (20 Hz or 120 Hz), (ii) monophasic or biphasic pulse shape (iii) continuous or intermittent DBS (20s on, 40s off) and 100 μA amplitude. Thereafter, rats were stimulated with the most effective parameter followed by 5-bromo-2'-deoxyuridine (BrdU) administration and perfused 4 weeks later. We then evaluated the effects of NBM DBS on hippocampal neurogenesis, synaptic plasticity, and on cholinergic fibres in the perirhinal and cingulate cortex using immunohistochemistry. We also performed in-vivo microdialysis to assess circuit-wide effects of NBM DBS on hippocampal acetylcholine levels during on and off stimulation.

RESULTS

Biphasic, low frequency and intermittent NBM DBS reversed the memory impairing effects of scopolamine when compared to sham rats. We found that acute stimulation promoted proliferation in the dentate gyrus, increased synaptic plasticity in the CA1 and CA3 subregion of the hippocampus, and increased length of cholinergic fibres in the cingulate gyrus. There was no difference regarding hippocampal acetylcholine levels between the groups.

CONCLUSION

These findings suggest that the potential mechanism of action of the induced memory enhancement through NBM DBS might be due to selective neuroplastic and neurochemical changes.

Olfactory function and discrimination ability in the elderly: a pilot study

We recently reported that subjects with a higher olfactory identification threshold for rose odor declined more in attentional ability in the elderly. This study focuses on discrimination ability and olfactory identification threshold in twelve elderly subjects living in a community (age: 80.9 ± 1.6). Olfactory function was assessed by the rose odor identification threshold. We assessed the discrimination ability by distinguishing 5 similar odor pairs. Our results showed that the subjects with a higher olfactory identification threshold (≥ 5) declined more in discrimination ability (14% ± 14%, p = 0.03) compared to those with a lower threshold (≤ 4) (averaged value set at 100%). As discrimination ability is related to the basal forebrain cholinergic system, our results suggest that olfactory impairment links to the decline in cognitive function relating the cholinergic system.

Impaired cerebral microcirculation in isolated REM sleep behaviour disorder

During the prodromal period of Parkinson's disease and other α-synucleinopathy-related parkinsonisms, neurodegeneration is thought to progressively affect deep brain nuclei, such as the locus coeruleus, caudal raphe nucleus, substantia nigra, and the forebrain nucleus basalis of Meynert. Besides their involvement in the regulation of mood, sleep, behaviour, and memory functions, these nuclei also innervate parenchymal arterioles and capillaries throughout the cortex, possibly to ensure that oxygen supplies are adjusted according to the needs of neural activity. The aim of this study was to examine whether patients with isolated REM sleep behaviour disorder, a parasomnia considered to be a prodromal phenotype of α-synucleinopathies, reveal microvascular flow disturbances consistent with disrupted central blood flow control. We applied dynamic susceptibility contrast MRI to characterize the microscopic distribution of cerebral blood flow in the cortex of 20 polysomnographic-confirmed patients with isolated REM sleep behaviour disorder (17 males, age range: 54-77 years) and 25 healthy matched controls (25 males, age range: 58-76 years). Patients and controls were cognitively tested by Montreal Cognitive Assessment and Mini Mental State Examination. Results revealed profound hypoperfusion and microvascular flow disturbances throughout the cortex in patients compared to controls. In patients, the microvascular flow disturbances were seen in cortical areas associated with language comprehension, visual processing and recognition and were associated with impaired cognitive performance. We conclude that cortical blood flow abnormalities, possibly related to impaired neurogenic control, are present in patients with isolated REM sleep behaviour disorder and associated with cognitive dysfunction. We hypothesize that pharmacological restoration of perivascular neurotransmitter levels could help maintain cognitive function in patients with this prodromal phenotype of parkinsonism.

Deep Brain Stimulation in Alzheimer's Disease: Targeting the Nucleus Basalis of Meynert

Alzheimer's disease (AD) is becoming a prevalent disease in the elderly population. Past decades have witnessed the development of drug therapies with varying targets. However, all drugs with a single molecular target fail to reverse or ameliorate AD progression, which ultimately results in cortical and subcortical network dysregulation. Deep brain stimulation (DBS) has been proven effective for the treatment of Parkinson's disease, essential tremor, and other neurological diseases. As such, DBS has also been gradually acknowledged as a potential therapy for AD. The current review focuses on DBS of the nucleus basalis of Meynert (NBM). As a critical component of the cerebral cholinergic system and the Papez circuit in the basal ganglia, the NBM plays an indispensable role in the subcortical regulation of memory, attention, and arousal state, which makes the NBM a promising target for modulation of neural network dysfunction and AD treatment. We summarized the intricate projection relations and functionality of the NBM, current approaches for stereotactic localization and evaluation of the NBM, and the therapeutic effects of NBM-DBS both in patients and animal models. Furthermore, the current shortcomings of NBM-DBS, such as variations in cortical blood flow, increased temperature in the target area, and stimulation-related neural damage, were presented.

The relationship between olfaction and cognitive function in the elderly

This study investigated the relationship between olfaction and cognitive function in 12 elderly people (age: 80.9 ± 1.6) living in the community. Olfactory function was assessed by the identification threshold for rose odor. Four cognitive measures consisting general cognitive ability assessed by Mini-Mental State Examination (MMSE), its sub-domains, and attentional ability assessed by drawing a line to connect the numbers consecutively (trail-making test part A; TMT-A), were assessed. Subjects with a higher olfactory threshold (≥ 5) declined more in the performance speed of TMT-A (73% ± 7%, p = 0.05) compared with those subjects with a lower threshold (≤ 4) (averaged value was set at 100%). Other cognitive statuses assessed by MMSE tended to decline in subjects with higher thresholds. Because attentional function relates to the basal forebrain cholinergic system, our results suggest that olfactory impairment links to the decline in cognitive function, particularly of attention-relating cholinergic function.

Lesions of the nucleus basalis magnocellularis (Meynert) induce enhanced somatosensory responses and tactile hypersensitivity in rats

We used the immunotoxin 192 immunoglobulin G-saporin to produce a selective cholinergic lesion in the nucleus basalis of Meynert (NBM) of rats and investigated whether the NBM lesion led to tactile hypersensitivity in the forepaw. The paw mechanical threshold test showed that the lesioned rats had a decreased threshold compared to the control. Surprisingly, there was a significant positive correlation between mechanical threshold and survival rate of NBM cholinergic neurons. Furthermore, using local field potential (LFP) recordings and voltage-sensitive dye (VSD) imaging, we found that the forepaw-evoked response in the primary somatosensory cortex (S1) was significantly enhanced in both amplitude and spatial extent in the NBM-lesioned rats. The neurophysiological measures of S1 response, such as LFP amplitude and maximal activated cortical area depicted by VSD, were also correlated with withdrawal behavior. Additional pharmacological experiments demonstrated that forepaw-evoked responses were increased in naive rats by blocking S1 cholinergic receptors with mecamylamine and scopolamine, while the response decreased in NBM-lesioned rats with the cholinergic agonist carbachol. In addition, NBM burst stimulation, which facilitates acetylcholine release in the S1, suppressed subsequent sensory responses to forepaw stimulation. Taken together, these results suggest that neuronal loss in the NBM diminishes acetylcholine actions in the S1, thereby enhancing the cortical representation of sensory stimuli, which may in turn lead to behavioral hypersensitivity.

Effects of nicotine on regional blood flow in the olfactory bulb in response to olfactory nerve stimulation

This study examined the effect of olfactory nerve stimulation on regional cerebral blood flow and assessed the effect of intravenous nicotine administration on this response in anesthetized rats. Regional cerebral blood flow was measured with laser Doppler flowmetry or laser speckle contrast imaging. Unilateral olfactory nerve stimulation for 5 s produced current (≥ 100 μA) and frequency-dependent (≥ 5 Hz) increases in blood flow in the olfactory bulb ipsilateral to the stimulus. The increased olfactory bulb blood flow peaked at 30 ± 7% using stimulus parameters of 300 μA and 20 Hz. Nerve stimulation did not change frontal cortical blood flow or mean arterial pressure. The intravenous injection of nicotine (30 μg/kg) augmented the olfactory bulb blood flow response to nerve stimulation (20 Hz, 300 μA) by approximately 1.5-fold (60-s area after the stimulation). These results indicate that olfactory nerve stimulation increases olfactory bulb blood flow, and the response is potentiated by the activation of nicotinic cholinergic transmission.

Characterizing Brain Connectivity From Human Electrocorticography Recordings With Unobserved Inputs During Epileptic Seizures

Epilepsy is a neurological disorder characterized by the sudden occurrence of unprovoked seizures. There is extensive evidence of significantly altered brain connectivity during seizure periods in the human brain. Research on analyzing human brain functional connectivity during epileptic seizures has been limited predominantly to the use of the correlation method. However, spurious connectivity can be measured between two brain regions without having direct connection or interaction between them. Correlations can be due to the apparent interactions of the two brain regions resulting from common input from a third region, which may or may not be observed. Hence, researchers have recently proposed a sparse-plus-latent-regularized precision matrix (SLRPM) when there are unobserved or latent regions interacting with the observed regions. The SLRPM method yields partial correlations of the conditional statistics of the observed regions given the latent regions, thus identifying observed regions that are conditionally independent of both the observed and latent regions. We evaluate the performance of the methods using a spring-mass artificial network and assuming that some nodes cannot be observed, thus constituting the latent variables in the example. Several cases have been considered, including both sparse and dense connections, short-range and long-range connections, and a varying number of latent variables. The SLRPM method is then applied to estimate brain connectivity during epileptic seizures from human ECoG recordings. Seventy-four clinical seizures from five patients, all having complex partial epilepsy, were analyzed using SLRPM, and brain connectivity was quantified using modularity index, clustering coefficient, and eigenvector centrality. Furthermore, using a measure of latent inputs estimated by the SLRPM method, it was possible to automatically detect 72 of the 74 seizures with four false positives and find six seizures that were not marked manually.

Acupuncture for Premenstrual Syndrome at Different Intervention Time: A Systemic Review and Meta-Analysis

Background

Premenstrual syndrome (PMS) is one of the most common gynecological conditions with no standard modern therapeutic schedule. Some studies have reported the effects of acupuncture in treating PMS, but the intervention time varies. This review evaluated the efficacy of acupuncture for patients with PMS and the appropriate time to initiate acupuncture therapy. The review has been registered on the “PROSPERO” website; the registration number is CRD42018109724.

Methods

A comprehensive literature search was performed on 9 electronic databases from the time of inception to September 2018. RCTs studies on acupuncture for PMS compared with medication, sham acupuncture, or no treatment were included. Statistical analysis and investigation of heterogeneity source were carried out using RevMan5. 3.

Results

A total of 15 studies, comprising of 1103 cases, were included. Overall, acupuncture significantly increased the effective rate of PMS compared with medicine and sham acupuncture. Subgroup analyses showed no significant difference among different intervention time to start acupuncture treatment. Among the acupoints involved in the treatment of PMS, SP6, LR3, and RN4 were the most commonly used.

Conclusions

The current meta-analysis reveals that acupuncture leads to better effective rate, but the intervention time has no significant effect on the efficacy of acupuncture treatment for PMS. SP6, LR3, and RN4 are the most commonly used acupoints in treating PMS. However, large-scale, case-control studies with rigorous designs are required to provide more accurate evidence.

Effects of nicotine on odor-induced increases in regional blood flow in the olfactory bulb in rats

The present study examined the effects of nicotinic acetylcholine receptor activation on the odor-induced blood flow response in the olfactory bulb. In urethane-anesthetized rats, odor stimulation (5% amyl acetate, 30 s) produced an increase in olfactory bulb blood flow (reaching 107% ± 3% of the pre-stimulus basal values), without changes in frontal cortical blood flow or mean arterial pressure. Intravenous injection of nicotine (30 μg/kg), a nicotinic acetylcholine receptor agonist, significantly augmented the odor-induced increase response of olfactory bulb blood flow, without changes in the basal blood flow level. The nicotine-induced augmentation of the olfactory bulb blood flow response to odor was negated by dihydro-β-erythroidine, an α4β2-preferring nicotinic acetylcholine receptor antagonist. Our results suggest that the activation of α4β2-like neuronal nicotinic acetylcholine receptors in the brain potentiates an odor-induced blood flow response in the olfactory bulb.

Blood pressure-independent increase in the cortical cerebral blood flow induced by manual acupuncture of the auricular region in rats

We aimed to determine whether acupuncture to the auricular region increases cortical regional cerebral blood flow (rCBF). The rCBF was measured using laser speckle contrast imaging in urethane-anesthetized rats. Acupuncture stimulation was performed manually at the auricular concha or abdomen. The former's stimulation significantly increased the rCBF of the bilateral cerebral cortex in the frontal, parietal, and occipital lobes without altering the systemic arterial pressure. In contrast, abdominal stimulation affected neither rCBF nor systemic arterial pressure. The increase in the rCBF was completely abolished by the severance of the somatic nerves that innervated the auricular region, comprising the trigeminal nerve, facial nerve, auricular branch of the vagal nerve, glossopharyngeal nerve, and great auricular nerve. Thus, application of acupuncture to the auricular region increases the rCBF without increasing arterial pressure.

Muscarinic M5 receptors trigger acetylcholine-induced Ca2+ signals and nitric oxide release in human brain microvascular endothelial cells

Basal forebrain neurons control cerebral blood flow (CBF) by releasing acetylcholine (Ach), which binds to endothelial muscarinic receptors to induce nitric (NO) release and vasodilation in intraparenchymal arterioles. Nevertheless, the mechanism whereby Ach stimulates human brain microvascular endothelial cells to produce NO is still unknown. Herein, we sought to assess whether Ach stimulates NO production in a Ca²⁺ -dependent manner in hCMEC/D3 cells, a widespread model of human brain microvascular endothelial cells. Ach induced a dose-dependent increase in intracellular Ca²⁺ concentration ([Ca²⁺ ]_i ) that was prevented by the genetic blockade of M5 muscarinic receptors (M5-mAchRs), which was the only mAchR isoform coupled to phospholipase Cβ (PLCβ) present in hCMEC/D3 cells. A comprehensive real-time polymerase chain reaction analysis revealed the expression of the transcripts encoding for type 3 inositol-1,4,5-trisphosphate receptors (InsP₃ R3), two-pore channels 1 and 2 (TPC1-2), Stim2, Orai1-3. Pharmacological manipulation showed that the Ca²⁺ response to Ach was mediated by InsP₃ R3, TPC1-2, and store-operated Ca²⁺ entry (SOCE). Ach-induced NO release, in turn, was inhibited in cells deficient of M5-mAchRs. Likewise, Ach failed to increase NO levels in the presence of l-NAME, a selective NOS inhibitor, or BAPTA, a membrane-permeant intracellular Ca²⁺ buffer. Moreover, the pharmacological blockade of the Ca²⁺ response to Ach also inhibited the accompanying NO production. These data demonstrate for the first time that synaptically released Ach may trigger NO release in human brain microvascular endothelial cells by stimulating a Ca²⁺ signal via M5-mAchRs.

The neuroprotective effect of deep brain stimulation at nucleus basalis of Meynert in transgenic mice with Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common type of dementia and mainly treated by drugs, while the therapeutic outcomes are very limited. This study aimed to determine the optimized parameters of deep brain stimulation (DBS) which was applied to the treatment of AD and propose the involved mechanisms.

METHODS

Amyloid-β precursor protein/Presenilin1 (APP/PS1) transgenic mice were used and received DBS at nucleus basalis of Meynert (NBM). The optimized parameters of DBS were determined by using different stimulation frequencies, durations and ages of mice under Morris water maze test. The involved mechanisms and the possible signal pathways were also investigated.

RESULTS

The optimized parameters for DBS were high frequency (100 Hz) for 21 days starting from early age (4 months old). Under the above parameters, the soluble Aβ40 and Aβ42 in the hippocampus and cortex were down-regulated significantly. DBS increased survival neurons and reduced apoptotic cells in the hippocampus and cortex. Meanwhile, the apoptosis-related proteins caspase-3, caspase-8 and Bid were down-regulated. Moreover, DBS caused a significant increase of superoxide dismutase, glutathione peroxidase and choline acetyltransferase activity as well as a decrease of methane dicarboxylic aldehyde content and acetylcholine esterase activity. Phosphorylation of Akt (p-Akt)/total Akt (t-Akt) was up-regulated while p-extracellular signal-regulated kinase 1/2 (ERK1/2)/t-ERK1/2 was down-regulated. The neuroprotective effect of DBS was attenuated by their inhibitors.

CONCLUSIONS

NBM-DBS starting from 4 months of age for 21 days at a high frequency (100 Hz) has therapeutic effects on AD through activating phosphatidylinositol 3'-kinase (PI3K)/Akt pathway and inhibiting ERK1/2 pathway.

Effect of basal forebrain stimulation on extracellular acetylcholine release and blood flow in the olfactory bulb

The olfactory bulb receives cholinergic basal forebrain input, as does the neocortex; however, the in vivo physiological functions regarding the release of extracellular acetylcholine and regulation of regional blood flow in the olfactory bulb are unclear. We used in vivo microdialysis to measure the extracellular acetylcholine levels in the olfactory bulb of urethane-anesthetized rats. Focal chemical stimulation by microinjection of L-glutamate into the horizontal limb of the diagonal band of Broca (HDB) in the basal forebrain, which is the main source of cholinergic input to the olfactory bulb, increased extracellular acetylcholine release in the ipsilateral olfactory bulb. When the regional cerebral blood flow was measured using laser speckle contrast imaging, the focal chemical stimulation of the HDB did not significantly alter the blood flow in the olfactory bulb, while increases were observed in the neocortex. Our results suggest a functional difference between the olfactory bulb and neocortex regarding cerebral blood flow regulation through the release of acetylcholine by cholinergic basal forebrain input.

Effects of electroacupuncture to the trigeminal nerve area on the autonomic nervous system and cerebral blood flow in the prefrontal cortex

BACKGROUND

The autonomic nervous system and trigeminal nerve are involved in adjusting flow through diverging cerebral arteries in the prefrontal cortex. The purpose of this study was to examine the effect of 100 Hz electroacupuncture (EA) to the trigeminal nerve area on cerebral blood flow and autonomic nervous system function.

METHOD

This was a randomised crossover study of 16 healthy volunteers who were assigned to an EA or control group. Stimulation (in the EA group) was performed five times, each after 1 min of rest. Needles were inserted at the inner edge of the eyebrows and 1 cm from the front hairline midpoint. We used high-frequency (HF) and low-frequency (LF) components of heart rate (HR) variability to assess autonomic nervous system function. HF and LF/HF ratio were taken as indicators of parasympathetic and sympathetic nervous system activity, respectively. We measured cerebral blood flow using a two-channel near-infrared spectroscope.

RESULTS

In the EA group, HR significantly decreased (p=0.004) and HF significantly increased (p=0.006) relative to baseline. By contrast, there were no significant changes in HR or HF within the control group (p>0.05). Accordingly, HR tended to be lower (p=0.087) and HF greater (p=0.071) in the EA group versus the control group. There were no significant differences in LF/HF ratio within/between groups. Compared with the control group, cerebral blood flow was significantly greater in the left (p=0.048) and right (p=0.016) prefrontal cortex in the EA group.

CONCLUSIONS

Delivery of 100 Hz EA to the trigeminal nerve area reduces HR and increases parasympathetic nervous activity and cerebral blood flow.

A murine toolbox for imaging the neurovascular unit

The neurovascular unit (NVU) coordinates many essential functions in the brain including blood flow control, nutrient delivery, and maintenance of BBB integrity. These functions are the result of a cellular and molecular interplay that we are just beginning to understand. Cells of the NVU can now be investigated in the intact brain through the combined use of high-resolution in vivo imaging and non-invasive molecular tools to observe and manipulate cell function. Mouse lines that target transgene expression to cells of the NVU will be of great value in future work. However, a detailed evaluation of target cell specificity and expression pattern within the brain is required for many existing lines. The purpose of this review was to catalog mouse lines available to cerebrovascular biologists and to discuss their utility and limitations in future imaging studies.

Effect of acupuncture-like stimulation on cortical cerebral blood flow in aged rats

This study aimed to examine the effect of acupuncture-like stimulation on cortical cerebral blood flow (CBF) in aged rats and the contribution of the intracranial cholinergic vasodilatory system on its response. In urethane-anesthetized rats of 30-37 months of age, manual acupuncture-like stimulation of a forepaw produced an increase in the CBF, independent of systemic arterial pressure. The increase in the CBF induced by forepaw stimulation was abolished by intravenous administration of cholinergic receptor antagonists. Manual acupuncture-like stimulation of a forepaw increased extracellular acetylcholine release in the cerebral cortex. These results suggest that natural somatic afferent stimulation, such as acupuncture-like stimulation, activates the intracranial - most likely, basal forebrain - cholinergic vasodilatory system in the cerebral cortex, even in extremely aged rats.

Effect of a steam foot spa on geriatric inpatients with cognitive impairment: a pilot study

Purpose

To investigate whether a steam foot spa improves cognitive impairment in geriatric inpatients.

Methods

Geriatric inpatients with cognitive impairment were given a steam foot spa treatment at 42°C for 20 minutes for 2 weeks (5 days/week). Physiological indicators such as blood pressure, percutaneous oxygen saturation, pulse, tympanic temperature, and sleep time and efficiency were assessed. Cognitive function and behavioral and psychological symptoms of dementia were assessed using the Mini-Mental State Examination, Dementia Mood Assessment Scale, and Dementia Behavior Disturbance scale.

Results

Significant decreases in systolic (P < 0.01) and diastolic blood pressure (P < 0.05) along with a significant increase in tympanic temperature (P < 0.01) were observed after the steam foot spas. A significant improvement was seen in the Mini-Mental State Examination score (P < 0.01) and the overall dementia severity items in Dementia Mood Assessment Scale (P < 0.05).

Limitations

Japanese people are very fond of foot baths. However, it is difficult to understand why inpatients cannot receive steam foot baths. In this study, a control group was not used. Raters and enforcers were not blinded.

Conclusion

The results of this pilot study suggest that steam foot spas mitigate cognitive impairment in geriatric inpatients.

Visceral influences on brain and behavior

Mental processes and their neural substrates are intimately linked to the homeostatic control of internal bodily state. There are a set of distinct interoceptive pathways that directly and indirectly influence brain functions. The anatomical organization of these pathways and the psychological/behavioral expressions of their influence appear along discrete, evolutionarily conserved dimensions that are tractable to a mechanistic understanding. Here, we review the role of these pathways as sources of biases to perception, cognition, emotion, and behavior and arguably the dynamic basis to the concept of self.

The missing link between long-term stimulation of nicotinic receptors and the increases of acetylcholine release and vasodilation in the cerebral cortex of aged rats

In adult rats (4-9 months), chronic nicotine infusion increases the basal level of acetylcholine (ACh) release in the cerebral cortex and enhances responses of cortical ACh release and cortical vasodilation elicited by nucleus basalis of Meynert (NBM) stimulation. In the present study, we examined whether these effects of nicotine are detected in aged rats. Aged rats (27-30 months) received sustained subcutaneous nicotine (100 μg/kg/h) or saline for 14 days. Under urethane anesthesia, ACh release and regional blood flow in the parietal cortex were measured. The basal level of ACh release in the cerebral cortex was not changed by chronic nicotine. In addition, the magnitudes of ACh release and vasodilation by NBM stimulation were similar between the saline-treated and nicotine-treated groups. The lack of an effect of chronic nicotine in aged rats may be due to a decrease in nicotinic receptors in the cerebral cortex during aging (Nordberg et al., J Neurosci Res 31:103-111, 1992).

Acupuncture affects regional blood flow in various organs

In this review, our recent studies using anesthetized animals concerning the neural mechanisms of vasodilative effect of acupuncture-like stimulation in various organs are briefly summarized. Responses of cortical cerebral blood flow and uterine blood flow are characterized as non-segmental and segmental reflexes. Among acupuncture-like stimuli delivered to five different segmental areas of the body; afferent inputs to the brain stem (face) and to the spinal cord at the cervical (forepaw), thoracic (chest or abdomen), lumbar (hindpaw) and sacral (perineum) levels, cortical cerebral blood flow was increased by stimuli to face, forepaw and hindpaw. The afferent pathway of the responses is composed of somatic groups III and IV afferent nerves and whose efferent nerve pathway includes intrinsic cholinergic vasodilators originating in the basal forebrain. Uterine blood flow was increased by cutaneous stimulation of the hindpaw and perineal area, with perineal predominance. The afferent pathway of the response is composed of somatic group II, III and IV afferent nerves and the efferent nerve pathway includes the pelvic parasympathetic cholinergic vasodilator nerves. Furthermore, we briefly summarize vasodilative regulation of skeletal muscle blood flow via a calcitonin gene-related peptide (CGRP) induced by antidromic activation of group IV somatic afferent nerves. These findings in healthy but anesthetized animals may be applicable to understanding the neural mechanisms improving blood flow in various organs following clinical acupuncture.

Effect of Moxibustion Stimulation of Various Skin Areas on Cortical Cerebral Blood Flow in Anesthetized Rats

The effect of moxibustion stimulation of various skin areas (cheek, forepaw, upper arm, chest, back, lower leg, hindpaw and perineum) on cerebral blood flow (CBF) of the parietal cortex was examined in anesthetized rats after eliminating emotional influences. Moxibustion stimulation was performed by burning a moxa cone of about 4 mg weight placed on the shaved skin. CBF of the parietal cortex was measured using a laser Doppler flowmeter. Stimulation of the cheek, forepaw, upper arm and hindpaw produced significant increases in CBF, but stimulation of the other areas did not produce significant responses. Moxibustion stimulation of the forepaw and hindpaw produced an increase in the mean arterial pressure (MAP), while stimulation of the other areas did not. After spinal transection at the 2nd thoracic level, the MAP response to stimulation of the forepaw was abolished, whereas the CBF response to stimulation of the forepaw remained. The CBF response in spinalized rats was not affected by cutting cervical sympathetic and facial parasympathetic nerves, while it was almost abolished by intravenous administration of muscarinic and nicotinic cholinergic blocking agents. The CBF response was abolished by crushing the brachial plexus ipsilateral to the stimulated side. It is suggested that the increase in CBF, independent of MAP and emotional responses, elicited by moxibustion stimulation is a reflex response whose afferent pathway is composed of somatic afferent nerves, and whose efferent pathway involves intracerebral cholinergic nerves. A contribution of endogenous opioids in the present CBF responses was neglected, because naloxone did not influence the CBF responses.

The effects of old, new and emerging medicines on metabolic aberrations in PCOS

Polycystic ovary syndrome (PCOS) is a common endocrine disorder in women of reproductive age that is associated with significant adverse short- and long-term health consequences. Multiple metabolic aberrations, such as insulin resistance (IR) and hyperinsulinaemia, high incidence of impaired glucose tolerance, visceral obesity, inflammation and endothelial dysfunction, hypertension and dyslipidemia are associated with the syndrome. Assessing the metabolic aberrations and their long term health impact in women with PCOS is challenging and becomes more important as therapeutic interventions currently available for the management of PCOS are not fully able to deal with all these consequences. Current therapeutic management of PCOS has incorporated new treatments resulting from the better understanding of the pathophysiology of the syndrome. The aim of this review is to summarize the effect of old, new and emerging therapies used in the management of PCOS, on the metabolic aberrations of PCOS.

The physiological basis of complementary and alternative medicines for polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine disorder that is characterized by chronic hyperandrogenic anovulation leading to symptoms of hirsutism, acne, irregular menses, and infertility. Multiple metabolic and cardiovascular risk factors are associated with PCOS, including insulin resistance, obesity, type 2 diabetes, hypertension, inflammation, and subclinical atherosclerosis. However, current treatments for PCOS are only moderately effective at controlling symptoms and preventing complications. This article describes how the physiological effects of major complementary and alternative medicine (CAM) treatments could reduce the severity of PCOS and its complications. Acupuncture reduces hyperandrogenism and improves menstrual frequency in PCOS. Acupuncture's clinical effects are mediated via activation of somatic afferent nerves innervating the skin and muscle, which, via modulation of the activity in the somatic and autonomic nervous system, may modulate endocrine and metabolic functions in PCOS. Chinese herbal medicines and dietary supplements may also exert beneficial physiological effects in PCOS, but there is minimal evidence that these CAM treatments are safe and effective. Mindfulness has not been investigated in PCOS, but it has been shown to reduce psychological distress and exert positive effects on the central and autonomic nervous systems, hypothalamic-pituitary-adrenal axis, and immune system, leading to reductions in blood pressure, glucose, and inflammation. In conclusion, CAM treatments may have beneficial endocrine, cardiometabolic, and reproductive effects in PCOS. However, most studies of CAM treatments for PCOS are small, nonrandomized, or uncontrolled. Future well-designed studies are needed to further evaluate the safety, effectiveness, and mechanisms of CAM treatments for PCOS.

Control of cerebral cortical blood flow by stimulation of basal forebrain cholinergic areas in mice

We examined whether activity of the nucleus basalis of Meynert (NBM) regulates regional cerebral cortical blood flow (rCBF) in mice, using laser speckle and laser Doppler flowmetry. In anesthetized mice, unilateral focal stimulation, either electrical or chemical, of the NBM increased rCBF of the ipsilateral cerebral cortex in the frontal, parietal and occipital lobes, independent of changes in systemic blood pressure. Most of vasodilative responses to low intensity stimuli (2 times threshold intensity: 2T) were abolished by atropine (a muscarinic cholinergic blocker), whereas responses to higher intensity stimuli (3T) were abolished by atropine and mecamylamine (a nicotinic cholinergic blocker). Blood flow changes were largest when the tip of the electrode was located within the area containing cholinergic neurons shown by choline acetyltransferase-immunocytochemistry. These results suggest that cholinergic projections from basal forebrain neurons in mice cause vasodilation in the ipsilateral cerebral cortex by a combination of muscarinic and nicotinic mechanisms, as previously found in rats and cats.

Association cortex hypoperfusion in mild dementia with Lewy bodies: a potential indicator of cholinergic dysfunction?

Dementia with Lewy bodies (DLB) is often associated with occipital hypometabolism or hypoperfusion, as well as deficits in cholinergic neurotransmission. In this study, 11 mild DLB, 16 mild AD and 16 age-matched controls underwent arterial spin-labeled perfusion MRI (ASL-pMRI) and neuropsychological testing. Patterns of cerebral blood flow (CBF) and cognitive performance were compared. In addition, combined ASL-pMRI and ChEI drug challenge (pharmacologic MRI) was tested as a probe of cholinergic function in 4 of the DLB participants. Frontal and parieto-occipital hypoperfusion was observed in both DLB and AD but was more pronounced in DLB. Following ChEI treatment, perfusion increased in temporal and parieto-occipital cortex, and cognitive performance improved on a verbal fluency task. If confirmed in a larger study, these results provide further evidence for brain cholinergic dysfunction in DLB pathophysiology, and use of pharmacologic MRI as an in vivo measure of cholinergic function.

Sustained subcutaneous infusion of nicotine enhances cholinergic vasodilation in the cerebral cortex induced by stimulation of the nucleus basalis of Meynert in rats

The present study examined the effects of sustained nicotine exposure on the cholinergic vasodilative system originating in the nucleus basalis of Meynert (NBM) and projecting to the cerebral cortex in rats. Rats received sustained subcutaneous nicotine (100μg/kg/h) for 14 days. Under urethane anesthesia, the vasodilation response and acetylcholine release in the parietal cortex induced by electrical stimulation of the NBM (10-200μA) were measured. The basal level of acetylcholine release was significantly higher in nicotine-treated rats than in saline-treated control rats. In the control rats, both the acetylcholine release and blood flow were increased by NBM stimulation in a stimulus intensity-dependent manner, and a threshold of 50μA. In nicotine-treated rats, the threshold intensity of NBM stimulation producing increases in acetylcholine release and blood flow was reduced to 20μA. The stimulus intensity-dependent acetylcholine release and vasodilation by NBM stimulation were significantly larger in nicotine-treated rats than in control rats. We conclude that sustained subcutaneous infusion of nicotine enhances cholinergic vasodilative system in the cerebral cortex originating in the NBM.

Aging of the autonomic nervous system and possible improvements in autonomic activity using somatic afferent stimulation

There are significant age-related changes in autonomic nervous system function that are responsible for an impaired ability to adapt to environmental or intrinsic visceral stimuli in the elderly. We review data on changes in autonomic nervous system regulation of cardiovascular and urinary function, as well as data on strategies to improve function. There are data showing alterations in peripheral and central autonomic nerve activity, and decreases in neurotransmitter receptor action that lead to diminished autonomic reactivity (e.g. blood pressure and cerebral blood flow regulation) and poorly coordinated autonomic discharge (e.g. bladder function). Simple strategies for autonomic function improvement and increasing cortical blood flow include walking and somatic afferent stimulation (e.g. stroking skin or acupuncture) to increase sympathetic, parasympathetic and central cholinergic activity.

Brain activation by short-term nicotine exposure in anesthetized wild-type and beta2-nicotinic receptors knockout mice: a BOLD fMRI study

RATIONALE

The behavioral effects of nicotine and the role of the beta2-containing nicotinic receptors in these behaviors are well documented. However, the behaviors altered by nicotine rely on the functioning on multiple brain circuits where the high-affinity beta2-containing nicotinic receptors (beta2*nAChRs) are located.

OBJECTIVES

We intend to see which brain circuits are activated when nicotine is given in animals naïve for nicotine and whether the beta2*nAChRs are needed for its activation of the blood oxygen level dependent (BOLD) signal in all brain areas.

MATERIALS AND METHODS

We used functional magnetic resonance imaging (fMRI) to measure the brain activation evoked by nicotine (1 mg/kg delivered at a slow rate for 45 min) in anesthetized C57BL/6J mice and beta2 knockout (KO) mice.

RESULTS

Acute nicotine injection results in a significant increased activation in anterior frontal, motor, and somatosensory cortices and in the ventral tegmental area and the substantia nigra. Anesthetized mice receiving no nicotine injection exhibited a major decreased activation in all cortical and subcortical structures, likely due to prolonged anesthesia. At a global level, beta2 KO mice were not rescued from the globally declining BOLD signal. However, nicotine still activated regions of a meso-cortico-limbic circuit likely via alpha7 nicotinic receptors.

CONCLUSIONS

Acute nicotine exposure compensates for the drop in brain activation due to anesthesia through the meso-cortico-limbic network via the action of nicotine on beta2*nAChRs. The developed fMRI method is suitable for comparing responses in wild-type and mutant mice.

Cerebral cortical blood flow response during basal forebrain stimulation in cats

We examined whether stimulation of the basal forebrain affects regional cerebral blood flow in the primary somatosensory cortex in cats. In anesthetized cats with spinal cord transection at the T1 level, focal electrical stimulation of the unilateral basal forebrain increased the blood flow of the ipsilateral primary somatosensory cortex that was increased by stimulation of the contralateral forepaw, without any change in blood pressure. The response was the largest when the tip of the electrode was located within the area known to contain the basal forebrain neurons projecting to the primary somatosensory cortex. These results suggest that basal forebrain neurons projecting to the primary somatosensory cortex have a vasodilative function in cats, as previously found in rats.

Basal forebrain cholinergic lesions reduce heat shock protein 72 response but not pathology induced by the NMDA antagonist MK-801 in the rat cingulate cortex

Non-competitive N-methyl-D-aspartate (NMDA) antagonists, in addition to their neuroprotective potential, possess neurotoxic properties and induce seizures and psychosis. MK-801 induces cytoplasmic vacuoles and heat shock protein in pyramidal neurones in the rodent posterior cingulate and retrosplenial cortex. The mechanism of this neurotoxicity is unclear, involving many neurotransmitter systems. The aim of this study was to investigate the role of cholinergic pathways from the nucleus basalis of Meynert in mediating MK-801-induced neurotoxicity. Cholinergic projections from the nucleus basalis of Meynert were lesioned by focal injection of 192-IgG-saporin (80 ng), which after 7 days reduced the number of cholinergic cell bodies by 70% in the lesioned nucleus compared to the uninjected nucleus. Following a unilateral cholinergic lesion, MK-801 (5 mg/kg s.c.) induced expression of hsp72 mRNA (6 h) and HSP72 protein immunoreactivity (24 h) was reduced by 42 and 60%, respectively in the ipsilateral compared to the contralateral posterior cingulate. Despite this apparent protective effect, the unilateral cholinergic lesion did not affect the degree of neuronal vacuolation (6 h), necrosis (24 h) or the large and prolonged increase in cerebral blood flow which occurred over the first 9h following MK-801 administration. These results demonstrate that cholinergic neurones in the nucleus basalis of Meynert play an important role in the heat shock response to NMDA antagonist-induced neurotoxicity but also reveal an unexpected divergence between the heat shock response and the pathophysiological response. This suggests that other cholinergic pathways or non-cholinergic mechanisms are responsible for the pathological changes induced by MK-801.

Effects of nicotine on regional blood flow in the olfactory bulb in rats

Effects of nicotine on blood flow in the olfactory bulb were examined in anesthetized rats. Nicotine administered intravenously at 100 microg/kg increased regional blood flow in the olfactory bulb, irrespective of changes in systemic arterial pressure. Nicotine administered locally into the internal carotid artery at 10 microg increased blood flow, without changing arterial pressure; this response was abolished by hexamethonium. These results indicate that nicotine produces vasodilatation in the olfactory bulb via activation of nicotinic receptors located close to the olfactory bulb. Nicotine may be of therapeutic value in improving blood flow in the olfactory bulb.

Preventive effect of chotosan, a Kampo medicine, on transient ischemia-induced learning deficit is mediated by stimulation of muscarinic M1 but not nicotinic receptor

We have previously shown using a water maze task that transient 2 vessel occlusion (T2VO) induced learning deficit in mice and that the deficit was prevented by pre-treatment of mice with chotosan, a Kampo prescription. In this study, we investigated the mechanism underlying the preventive effect of chotosan on T2VO-induced learning deficit. Chotosan administration 1 h before T2VO operation prevented learning impairment. The extract of Uncaria, a major constituent of chotosan, also had a protective effect on learning impairment in T2VO mice, whereas Uncaria-free chotosan had no beneficial effect on maze performance of T2VO mice. The ameliorative effect of chotosan was blocked by pirenzepine, a muscarinic M1 antagonist, but not by mecamylamine, a nicotinic receptor antagonist. Acetylcholine (ACh) content in the hippocampus of T2VO mice was significantly lower than that in the hippocampus of sham-operated control mice. Chotosan and Uncaria administration attenuated T2VO-induced reduction of ACh levels in the brain. These results suggest that the preventive effect of chotosan on transient ischemia-induced learning impairment is mainly attributable to the effect of Uncaria and that the ameliorative effect is mediated by stimulation of muscarinic M1 receptor.

Responses of Acetylcholine Release and Regional Blood Flow in the Hippocampus during Walking in Aged Rats

Walking produced increases in both the extracellular acetylcholine level and regional blood flow in the hippocampus in aged rats 26-29 months old. The present results in aged rats were compared with our previous data in young adult rats (Nakajima et al., 2003), and it was found that both the acetylcholine and blood flow responses in the hippocampus were well maintained in aged rats.

Cerebral regional cortical blood flow response during joint stimulation in cats

Noxious stimulation of an elbow joint in the anesthetized cat increases cerebral blood flow over broad, bilateral areas of the cerebral cortex and increases systemic blood pressure. In order to eliminate the confounding effects of elevated blood pressure on cerebral blood flow, we re-examined this phenomenon in cats with a transected spinal cord at the T1 level. Noxious stimulation of an elbow joint resulted in a significant increase in blood flow in the forelimb area of the contralateral primary somatosensory cortex; the blood pressure remained unchanged. These data in cats suggest that the previously described bilateral increase in cerebral blood flow following noxious joint stimulation was due, in part, to the increased blood pressure.

Hemodynamics under Hippocampal Functional Hyperemia in Anesthetized Rat: A Greater Contribution of Red Blood Cell Velocity Compared to Its Concentration

It remains controversial which of the two regulators, red blood cell velocity (RBC-V) or concentration (RBC-C), is a main contributor to increasing flow (RBC-F) during functional hyperemia in the rat hippocampus induced by N-methyl-D-aspartate (NMDA). To address this, we monitored these parameters simultaneously under NMDA-infusion via microdialysis in the hippocampus of urethane-anesthetized rats and found a greater elevation in RBC-V than in RBC-C. This suggests that an RBC-V-dependent increase in RBC-F occurs under NMDA-induced functional hyperemia in the hippocampus as well as in the cortex.