A New Target of Electroacupuncture Pretreatment Mediated Sympathetic Nervous to Improve MIRI: Glutamatergic Neurons in Fastigial Nucleus of the Cerebellum

Ischemic heart disease is a fatal cardiovascular disease that irreversibly impairs the function of the heart, followed by reperfusion leading to a further increase in infarct size. Clinically, we call it myocardial ischemia-reperfusion injury (MIRI). A growing number of clinical observations and experimental studies have found electroacupuncture (EA) to be effective in alleviating MIRI. This study attempts to investigate whether glutamatergic neurons in fastigial nucleus (FN) of the cerebellum are involved in EA pretreatment to alleviate MIRI via sympathetic nerves, and the potential mechanisms of EA pretreatment process. A MIRI model was established by ligating the coronary artery of the left anterior descending branch of the heart for 30 minutes, followed by 2 hours of reperfusion. Multichannel physiological recordings, electrocardiogram, cardiac ultrasound, chemical genetics, enzyme-linked immunosorbent assay and immunofluorescence staining methods were combined to demonstrate that EA pretreatment inhibited neuronal firing and c-Fos expression in FN of the cerebellum and reduced cardiac sympathetic firing. Meanwhile, EA pretreatment significantly reduced cardiac ejection fraction (EF), shortening fraction (SF), percentage infarct area, decreased myocardial norepinephrine (NE), creatine kinase isoenzyme MB (CK-MB) concentrations, and improved MIRI-induced myocardial tissue morphology. The results were similar to the inhibition of glutamatergic neurons in FN. However, the activation of glutamatergic neurons in FN diminished the aforementioned effects of EA pretreatment. This study revealed that glutamatergic neurons in FN of the cerebellum is involved in EA pretreatment mediated sympathetic nervous and may be a potential mediator for improving MIRI.

[Effects of electroacupuncture pretreatment on GABAA receptor of fastigial nucleus and sympathetic nerve activity in rats with myocardial ischemia reperfusion injury]

OBJECTIVE

To observe the effects of electroacupuncture (EA) pretreatment on cardiac function, sympathetic nerve activity, indexes of myocardial injury and GABA_A receptor in fastigial nucleus in rats with myocardial ischemia reperfusion injury (MIRI), and to explore the neuroregulatory mechanism of EA pretreatment in improving MIRI.

METHODS

A total of 60 male SD rats were randomly divided into a sham operation group, a model group, an EA group, an agonist group and an agonist+EA group, 12 rats in each group. The MIRI model was established by ligation of the left anterior descending coronary artery. EA was applied at bilateral "Shenmen" (HT 7) and "Tongli" (HT 5) in the EA group and the agonist+EA group, with continuous wave, in frequency of 2 Hz and intensity of 1 mA, 30 min each time, once a day for 7 consecutive days. After intervention, the MIRI model was established. In the agonist group, the muscone (agonist of GABA_A receptor, 1 g/L) was injected in fastigial nucleus for 7 consecutive days before modeling, 150 μL each time, once a day. In the agonist+EA group, the muscone was injected in fastigial nucleus 30 min before EA intervention. The data of electrocardiogram was collected by PowerLab standard Ⅱ lead, and ST segment displacement and heart rate variability (HRV) were analyzed; the serum levels of norepinephrine (NE), creatine kinase isoenzyme MB (CK-MB) and cardiac troponin I (cTnI) were detected by ELISA; the myocardial infarction area was measured by TTC staining; the morphology of myocardial tissue was observed by HE staining; the positive expression and mRNA expression of GABA_A receptor in fastigial nucleus were detected by immunohistochemistry and real-time PCR.

RESULTS

Compared with the sham operation group, in the model group, ST segment displacement and ratio of low frequency to high frequency (LF/HF) of HRV were increased (P<0.01), HRV frequency domain analysis showed enhanced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were increased (P<0.01), the percentage of myocardial infarction area was increased (P<0.01), myocardial fiber was broken and interstitial edema was serious, the positive expression and mRNA expression of GABA_A receptor in fastigial nucleus were increased (P<0.01). Compared with the model group, in the EA group, ST segment displacement and LF/HF ratio were decreased (P<0.01), HRV frequency domain analysis showed reduced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were decreased (P<0.01), the percentage of myocardial infarction area was decreased (P<0.01), myocardial fiber breakage and interstitial edema were lightened, the positive expression and mRNA expression of GABA_A receptor in fastigial nucleus were decreased (P<0.01). Compared with the EA group, in the agonist group and the agonist+EA group, ST segment displacement and LF/HF ratio were increased (P<0.01), HRV frequency domain analysis showed enhanced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were increased (P<0.01), the percentage of myocardial infarction area was increased (P<0.01), myocardial fiber breakage and interstitial edema were aggravated, the positive expression and mRNA expression of GABA_A receptor in fastigial nucleus were increased (P<0.01).

CONCLUSION

EA pretreatment can improve the myocardial injury in MIRI rats, and its mechanism may be related to the inhibition of GABA_A receptor expression in fastigial nucleus, thereby down-regulating the excitability of sympathetic nerve.

Cerebellar fastigial nucleus electrostimulation attenuates inflammation in a Post-Infarction rat model by activating cholinergic anti-inflammatory pathways

There are negative correlations between indices of heart rate variability (HRV) and markers of inflammation. The inflammation plays an important role in myocardial damages after myocardial infarction (MI). Our previous study found that fastigial nucleus electrostimulation (FNS) improved abnormal HRV in a rat model of MI. Whether and how it can reduce inflammation and improve cardiac function after MI and the underlying mechanisms remain unknown. 66 Sprague Dawley rats were randomly divided into 4 groups as follows: i) Sham operation group (Sham); ii) Myocardial infarction group (MI); iii) FNS+MI group (FNS plus MI): left fastigial nucleus electrostimulation; iv) FNL+FNS+MI group (left fastigial nucleus lesion plus FNS plus MI). The serum expressions of acetylcholine (ACh), pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and anti-inflammatory cytokines IL-10 after FNS were measured using ELISA. Subsequently, the infarct size, the infiltration of inflammatory cells, the fibrotic area, and cardiac function were also evaluated. Additionally, the effects of FNS on the cholinergic anti-inflammatory pathway (CAP)-related proteins expression were determined by Western blot. We found that FNS significantly upregulated ACh and IL-10 expressions in serum, and decreased TNF-α and IL-6 levels. FNS significantly attenuated inflammatory cell infiltration and infarct size, decreased fibrosis, increased left ventricular ejection fraction (LVEF), and reduced mortality. Besides, the levels of p-STAT3/STAT3 and p-NF-κB/NF-κB significantly elevated after MI. FNS down-regulated the expression of p-STAT3/STAT3 and p-NF-κB/NF-κB. The protective effects of FNS were partially reversed by the fastigial nucleus lesion. Our data suggested that FNS can alleviate the inflammation after MI, and its cardiac neuroprotective mechanism may be achieved by increasing vagus tone, releasing ACh, and further activating the CAP via α7nAChR. The precise mechanism remains to be elucidated.

The involvement of Pellino-1 downregulation in the modulation of visceral hypersensitivity via the TLR4/NF-κB pathway in the rat fastigial nucleus

Irritable bowel syndrome (IBS) is a common functional bowel disorder whose key characteristics include chronic visceral hypersensitivity (CVH) and abnormal brain-gut interactions. Pellino-1 is an E3 ubiquitin ligase, mediating the degradation or modification of targeted proteins. Some brain regions, such as the fastigial nucleus (FN), may play important roles in CVH; however, the molecular mechanism underlying this phenomenon is not clear. In this study, we assessed the roles of Pellino-1 within the FN in modulating VH by generating a colorectal distention (CRD) model in male Sprague-Dawley rats. Our results showed that the downregulation of Pellino-1 in the fastigial nucleus (FN) was involved in the modulation of visceral hypersensitivity. The expression of Pellino-1 was downregulated in the FN of adult CRD rats compared with control rats, whereas TLR4 and NF-κB were upregulated in the CRD model. To overexpress Pellino-1, a lentivirus specifically expressing Pellino-1 and green fluorescent protein was administered into the FN. The overexpression of Pellino-1 increased the visceral sensitivity of CRD rats, and the expression of TLR4 and NF-κB increased further. After administration of TAK-242 (a specific TLR4 inhibitor), the visceral response to overexpression of Pellino-1 was reversed. Overall, the findings indicated the involvement of the FN in the development of CVH; the downregulation of Pellino-1 in the FN acted through the TLR4/NF-κB pathway to protect against CVH in a CRD rat model.

Distinct Fastigial Output Channels and Their Impact on Temporal Lobe Seizures

Despite being canonically considered a motor control structure, the cerebellum is increasingly recognized for important roles in processes beyond this traditional framework, including seizure suppression. Excitatory fastigial neurons project to a large number of downstream targets, and it is unclear whether this broad targeting underlies seizure suppression, or whether a specific output may be sufficient. To address this question, we used the intrahippocampal kainic acid mouse model of temporal lobe epilepsy, male and female animals, and a dual-virus approach to selectively label and manipulate fastigial outputs. We examined fastigial neurons projecting to the superior colliculus, medullary reticular formation, and central lateral nucleus of the thalamus, and found that these comprise largely nonoverlapping populations of neurons that send collaterals to unique sets of additional, somewhat overlapping, thalamic and brainstem regions. We found that neither optogenetic stimulation of superior colliculus nor reticular formation output channels attenuated hippocampal seizures. In contrast, on-demand stimulation of fastigial neurons targeting the central lateral nucleus robustly inhibited seizures. Our results indicate that fastigial control of hippocampal seizures does not require simultaneous modulation of many fastigial output channels. Rather, selective modulation of the fastigial output channel to the central lateral thalamus, specifically, is sufficient for seizure control. More broadly, our data highlight the concept of specific cerebellar output channels, whereby discrete cerebellar nucleus neurons project to specific aggregates of downstream targets, with important consequences for therapeutic interventions.SIGNIFICANCE STATEMENT The cerebellum has an emerging relationship with nonmotor systems and may represent a powerful target for therapeutic intervention in temporal lobe epilepsy. We find, as previously reported, that fastigial neurons project to numerous brain regions via largely segregated output channels, and that projection targets cannot be predicted simply by somatic locations within the nucleus. We further find that on-demand optogenetic excitation of fastigial neurons projecting to the central lateral nucleus of the thalamus-but not fastigial neurons projecting to the reticular formation, superior colliculus, or ventral lateral thalamus-is sufficient to attenuate hippocampal seizures.

Cerebellar modulation of synaptic input to freezing-related neurons in the periaqueductal gray

Innate defensive behaviors, such as freezing, are adaptive for avoiding predation. Freezing-related midbrain regions project to the cerebellum, which is known to regulate rapid sensorimotor integration, raising the question of cerebellar contributions to freezing. Here, we find that neurons of the mouse medial (fastigial) cerebellar nuclei (mCbN), which fire spontaneously with wide dynamic ranges, send glutamatergic projections to the ventrolateral periaqueductal gray (vlPAG), which contains diverse cell types. In freely moving mice, optogenetically stimulating glutamatergic vlPAG neurons that express Chx10 reliably induces freezing. In vlPAG slices, mCbN terminals excite ~20% of neurons positive for Chx10 or GAD2 and ~70% of dopaminergic TH-positive neurons. Stimulating either mCbN afferents or TH neurons augments IPSCs and suppresses EPSCs in Chx10 neurons by activating postsynaptic D2 receptors. The results suggest that mCbN activity regulates dopaminergic modulation of the vlPAG, favoring inhibition of Chx10 neurons. Suppression of cerebellar output may therefore facilitate freezing.

Hyper-Formation of GABA and Glycine Co-Releasing Terminals in the Mouse Cerebellar Nuclei after Deprivation of GABAergic Inputs from Purkinje Cells

GABA and glycine are inhibitory neurotransmitters. However, the mechanisms underlying the formation of GABAergic and glycinergic synapses remain unclear. The influence of GABAergic input deprivation on inhibitory terminal formation was investigated using Purkinje cell (PC)-specific vesicular GABA transporter (VGAT) knockout (L7-VGAT) mice, in which GABA release from PCs diminishes in an age-dependent manner. We compared the late development of GABAergic and glycinergic terminals in the cerebellar nucleus (CN) between control and L7-VGAT mice. In the control CN, the density of glutamate decarboxylase (GAD)-positive dots remained unchanged between postnatal 2 months (P2M) and 13 months (P13M), whereas glycine transporter 2 (GlyT2)-positive dots increased in density during this time frame. No difference in the density of GlyT2-positive dots was observed between control and L7-VGAT mice at P2M, but the density was significantly higher in the L7-VGAT fastigial nuclei (FN) than the control FN at P13M. When VGAT was absent from PC terminals, GlyT2-positive dots included GAD and VGAT and formed synapses. These results indicated that GABAergic terminals were formed by P2M, glycinergic terminals were actively formed after P2M, and more glycinergic terminals were formed in the L7-VGAT FN than in the control FN, suggesting that the increased glycinergic terminals may derive from interneurons within the FN and may also release GABA. These results suggest that the deprivation of GABAergic inputs from PCs may accelerate the formation of co-releasing terminals derived from interneurons and that the inhibitory terminal numbers and types may be regulated by the quantity of functional GABAergic inputs.

Excitation, but not inhibition, of the fastigial nucleus provides powerful control over temporal lobe seizures

KEY POINTS

On-demand optogenetic inhibition of glutamatergic neurons in the fastigial nucleus of the cerebellum does not alter hippocampal seizures in a mouse model of temporal lobe epilepsy. In contrast, on-demand optogenetic excitation of glutamatergic neurons in the fastigial nucleus successfully inhibits hippocampal seizures. With this approach, even a single 50 ms pulse of light is able to significantly inhibit seizures. On-demand optogenetic excitation of glutamatergic fastigial neurons either ipsilateral or contralateral to the seizure focus is able to inhibit seizures. Selective excitation of glutamatergic nuclear neurons provides greater seizure inhibition than broadly exciting nuclear neurons without cell-type specificity.

ABSTRACT

Temporal lobe epilepsy is the most common form of epilepsy in adults, but current treatment options provide limited efficacy, leaving as many as one-third of patients with uncontrolled seizures. Recently, attention has shifted towards more closed-loop therapies for seizure control, and on-demand optogenetic modulation of the cerebellar cortex was shown to be highly effective at attenuating hippocampal seizures. Intriguingly, both optogenetic excitation and inhibition of cerebellar cortical output neurons, Purkinje cells, attenuated seizures. The mechanisms by which the cerebellum impacts seizures, however, are unknown. In the present study, we targeted the immediate downstream projection of vermal Purkinje cells - the fastigial nucleus - in order to determine whether increases and/or decreases in fastigial output can underlie seizure cessation. Though Purkinje cell input to fastigial neurons is inhibitory, direct optogenetic inhibition of the fastigial nucleus had no effect on seizure duration. Conversely, however, fastigial excitation robustly attenuated hippocampal seizures. Seizure cessation was achieved at multiple stimulation frequencies, regardless of laterality relative to seizure focus, and even with single light pulses. Seizure inhibition was greater when selectively targeting glutamatergic fastigial neurons than when an approach that lacked cell-type specificity was used. Together, these results suggest that stimulating excitatory neurons in the fastigial nucleus may be a promising approach for therapeutic intervention in temporal lobe epilepsy.

Premotor Cortical-Cerebellar Reorganization in a Macaque Model of Primary Motor Cortical Lesion and Recovery

Neuromotor systems have the capacity for functional recovery following local damage. The literature suggests a possible role for the premotor cortex and cerebellum in motor recovery. However, the specific changes to interactions between these areas following damage remain unclear. Here, we demonstrate potential rewiring of connections from the ipsilesional ventral premotor cortex (ip-PMv) to cerebellar structures in a nonhuman primate model of primary motor cortex (M1) lesion and motor recovery. Cerebellar connections arising from the ip-PMv were investigated by comparing biotinylated dextran amine (BDA) between two groups of male Macaca mulatta: M1-lesion/motor recovery group and intact group. There were more BDA-labeled boutons and axons in all ipsilesional deep cerebellar nuclei (fastigial, interposed, and dentate) in the M1-lesion/recovery group than in the intact group. The difference was evident in the ipsilesional fastigial nucleus (ip-FN), and particularly observed in its middle, a putative somatosensory region of the ip-FN, which was characterized by absent or little expression of aldolase C. Some of the altered projections from the ip-PMv to ip-FN neurons were confirmed as functional because the synaptic markers, synaptophysin and vesicular glutamate transporter 1, were colocalized with BDA-labeled boutons. These results suggest that the adult primate brain after motor lesions can reorganize large-scale networks to enable motor recovery by enhancing sensorimotor coupling and motor commands via rewired fronto-cerebellar connections.SIGNIFICANCE STATEMENT Damaging the motor cortex causes motor deficits, which can be recovered over time. Such motor recovery may result from functional compensation in remaining neuromotor areas, including the ventral premotor cortex. We investigated compensatory changes in neural axonal outputs from ventral premotor to deep cerebellar nuclei in a monkey model of primary motor cortical lesion and motor recovery. The results showed an increase in premotor projections and synaptic formations in deep cerebellar nuclei, especially the sensorimotor region of the fastigial nucleus. Our results provide the first evidence that large-scale reorganization of fronto-cerebellar circuits may underlie functional recovery after motor cortical lesions.

Cerebellar fastigial nucleus is involved in post-stroke depression through direct cerebellar-hypothalamic GABAergic and glutamatergic projections

The present study aimed to investigate whether the cerebellar fastigial nucleus (FN) is involved in post-stroke depression (PSD), and to observe the effect of direct cerebellar-hypothalamic γ-aminobutyric acid (GABA)ergic and glutamatergic projections on PSD, in order to understand the mechanisms underlying the cerebellar modulation of mood and emotion. Healthy Sprague-Dawley rats were randomly divided into five groups: Sham-operated, Stroke, PSD, FN lesion, and decussation of superior cerebellar peduncle (XSCP) lesion groups. Sham surgery was performed in animals of the Sham group (n=6). The rats in the other four groups (n=6 for each group) underwent middle cerebral artery occlusion. The rats were examined twice a week in an open field test. In addition, the expression of cytokines in hippocampal tissues, and the content of glutamate and GABA in the lateral hypothalamic area (LHA) were measured. The results showed that scores corresponding to the behavioral signs of depression were decreased in the PSD, FN lesion and XSCP lesion groups. In addition, the mRNA levels of tumor necrosis factor-α, interleukin (IL)-6, and IL-1β in the hippocampus of the PSD, FN lesion and XSCP lesion groups were significantly increased. The GABA and glutamate content in the LHA were also decreased significantly in the PSD, FN lesion and XSCP lesion groups. Taken together, the findings of the present study indicated that the cerebellar FN may be involved in PSD through the direct cerebellar-hypothalamic glutamatergic and GABAergic projections.

Integrity of Cerebellar Fastigial Nucleus Intrinsic Neurons Is Critical for the Global Ischemic Preconditioning

Excitation of intrinsic neurons of cerebellar fastigial nucleus (FN) renders brain tolerant to local and global ischemia. This effect reaches a maximum 72 h after the stimulation and lasts over 10 days. Comparable neuroprotection is observed following sublethal global brain ischemia, a phenomenon known as preconditioning. We hypothesized that FN may participate in the mechanisms of ischemic preconditioning as a part of the intrinsic neuroprotective mechanism. To explore potential significance of FN neurons in brain ischemic tolerance we lesioned intrinsic FN neurons with excitotoxin ibotenic acid five days before exposure to 20 min four-vessel occlusion (4-VO) global ischemia while analyzing neuronal damage in Cornu Ammoni area 1 (CA1) hippocampal area one week later. In FN-lesioned animals, loss of CA1 cells was higher by 22% compared to control (phosphate buffered saline (PBS)-injected) animals. Moreover, lesion of FN neurons increased morbidity following global ischemia by 50%. Ablation of FN neurons also reversed salvaging effects of five-minute ischemic preconditioning on CA1 neurons and morbidity, while ablation of cerebellar dentate nucleus neurons did not change effect of ischemic preconditioning. We conclude that FN is an important part of intrinsic neuroprotective system, which participates in ischemic preconditioning and may participate in naturally occurring neuroprotection, such as "diving response".

Individual neurons in the caudal fastigial oculomotor region convey information on both macro- and microsaccades

Recent studies have suggested that microsaccades, the small amplitude saccades made during fixation, are precisely controlled. Two lines of evidence suggest that the cerebellum plays a key role not only in improving the accuracy of macrosaccades but also of microsaccades. First, lesions of the fastigial oculomotor regions (FOR) cause horizontal dysmetria of both micro- and macrosaccades. Secondly, our previous work on Purkinje cell simple spikes in the oculomotor vermis (OV) has established qualitatively similar response preferences for these two groups of saccades. In this work, we investigated the control signals for micro- and macrosaccades in the FOR, the target of OV Purkinje cell axons. We found that the same FOR neurons discharged for micro- and macrosaccades. For both groups of saccades, FOR neurons exhibited very similar dependencies of their discharge strength on direction and amplitude and very similar burst onset time differences for ipsi- and contraversive saccades and, in both, response duration reflected saccade duration, at least at the population level. An intriguing characteristic of microsaccade-related responses is that immediate pre-saccadic firing rates decreased with distance to the target center, a pattern that strikingly parallels the eye position dependency of both microsaccade metrics and frequency, which may suggest a potential neural mechanism underlying the role of FOR in fixation. Irrespective of this specific consideration, our study supports the view that microsaccades and macrosaccades share the same cerebellar circuitry and, in general, further strengthens the notion of a microsaccade-macrosaccade continuum.

Protective effect of histamine microinjected into the cerebellar fastigial nucleus on stress-induced gastric mucosal damage in rats

AIMS

We investigated the effffects and the possible mechanism of microinjection of histamine into cerebellar fastigial nucleus (FN) on stress-induced gastric mucosal damage (SGMD) in rats. The effect of microinjection of histamine into FN on SGMD was observed.

METHODS

The model of SGMD was established by restraint and water (21 ± 1°C)-immersion (RWI) for 3 h in rats. The gastric mucosal damage index indicated the severity of SGMD. Western blotting was performed to assess gastric mucosal cell apoptosis and proliferation.

RESULTS

We observed that histamine microinjection into the FN markedly attenuated SGMD in a dose-dependent manner, and was prevented by pre-treatment with the ranitidine (a selective histamine H2 receptor antagonist) into the FN. The effect of histamine was abolished by pre-treatment with 3-MPA (a glutamic acid decarboxylase antagonist) into the FN. There was a decrease in the discharge frequency of greater splanchnic nerve, and an increase in gastric mucosal blood flow after histamine injection into the FN. Additionally, anti-apoptotic and anti-oxidative factors of gastric mucosa might be involved in this process.

CONCLUSION

The exogenous histamine in FN participates in the regulation of SGMD, and our results may help to provide new ideas on the treatment of gastroenterological diseases.

Neuronal apoptosis in cerebral ischemia/reperfusion area following electrical stimulation of fastigial nucleus

Previous studies have indicated that electrical stimulation of the cerebellar fastigial nucleus in rats may reduce brain infarct size, increase the expression of Ku70 in cerebral ischemia/reperfusion area, and decrease the number of apoptotic neurons. However, the anti-apoptotic mechanism of Ku70 remains unclear. In this study, fastigial nucleus stimulation was given to rats 24, 48, and 72 hours before cerebral ischemia/reperfusion injury. Results from the electrical stimulation group revealed that rats exhibited a reduction in brain infarct size, a significant increase in the expression of Ku70 in cerebral ischemia/reperfusion regions, and a decreased number of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells. Double immunofluorescence staining revealed no co-localization of Ku70 with TUNEL-positive cells. However, Ku70 partly co-localized with Bax protein in the cytoplasm of rats with cerebral ischemia/reperfusion injury. These findings suggest an involvement of Ku70 with Bax in the cytoplasm of rats exposed to electrical stimulation of the cerebellar fastigial nucleus, and may thus provide an understanding into the anti-apoptotic activity of Ku70 in cerebral ischemia/reperfusion injury.

Back to front: cerebellar connections and interactions with the prefrontal cortex

Although recent neuroanatomical evidence has demonstrated closed-loop connectivity between prefrontal cortex and the cerebellum, the physiology of cerebello-cerebral circuits and the extent to which cerebellar output modulates neuronal activity in neocortex during behavior remain relatively unexplored. We show that electrical stimulation of the contralateral cerebellar fastigial nucleus (FN) in awake, behaving rats evokes distinct local field potential (LFP) responses (onset latency ~13 ms) in the prelimbic (PrL) subdivision of the medial prefrontal cortex. Trains of FN stimulation evoke heterogeneous patterns of response in putative pyramidal cells in frontal and prefrontal regions in both urethane-anesthetized and awake, behaving rats. However, the majority of cells showed decreased firing rates during stimulation and subsequent rebound increases; more than 90% of cells showed significant changes in response. Simultaneous recording of on-going LFP activity from FN and PrL while rats were at rest or actively exploring an open field arena revealed significant network coherence restricted to the theta frequency range (5–10 Hz). Granger causality analysis indicated that this coherence was significantly directed from cerebellum to PrL during active locomotion. Our results demonstrate the presence of a cerebello-prefrontal pathway in rat and reveal behaviorally dependent coordinated network activity between the two structures, which could facilitate transfer of sensorimotor information into ongoing neocortical processing during goal directed behaviors.

Convergent synaptic inputs from the caudal fastigial nucleus and the superior colliculus onto pontine and pontomedullary reticulospinal neurons

The caudal fastigial nucleus (FN) is known to be related to the control of eye movements and projects mainly to the contralateral reticular nuclei where excitatory and inhibitory burst neurons for saccades exist [the caudal portion of the nucleus reticularis pontis caudalis (NRPc), and the rostral portion of the nucleus reticularis gigantocellularis (NRG) respectively]. However, the exact reticular neurons targeted by caudal fastigioreticular cells remain unknown. We tried to determine the target reticular neurons of the caudal FN and superior colliculus (SC) by recording intracellular potentials from neurons in the NRPc and NRG of anesthetized cats. Neurons in the rostral NRG received bilateral, monosynaptic excitation from the caudal FNs, with contralateral predominance. They also received strong monosynaptic excitation from the rostral and caudal contralateral SC, and disynaptic excitation from the rostral ipsilateral SC. These reticular neurons with caudal fastigial monosynaptic excitation were not activated antidromically from the contralateral abducens nucleus, but most of them were reticulospinal neurons (RSNs) that were activated antidromically from the cervical cord. RSNs in the caudal NRPc received very weak monosynaptic excitation from only the contralateral caudal FN, and received either monosynaptic excitation only from the contralateral caudal SC, or monosynaptic and disynaptic excitation from the contralateral caudal and ipsilateral rostral SC, respectively. These results suggest that the caudal FN helps to control also head movements via RSNs targeted by the SC, and these RSNs with SC topographic input play different functional roles in head movements.

Neurogenic neuroprotection: clinical perspectives

Neurogenic neuroprotection is a promising approach for treating patients with ischemic brain lesions. In rats, stimulation of the deep brain nuclei has been shown to reduce the volume of focal infarction. In this context, protection of neural tissue can be a rapid intervention that has a relatively long-lasting effect, making fastigial nucleus stimulation (FNS) a potentially valuable method for clinical application. Although the mechanisms of neuroprotection induced by FNS remain partially unclear, important data have been presented in the last two decades. A 1-h electrical FNS reduced, by 59%, infarctions triggered by permanent occlusion of the middle cerebral artery in Fisher rats. The acute effect of electrical FNS is likely mediated by a prolonged opening of potassium channels, and the sustained effect appears to be linked to inhibition of the apoptotic cascade. A better understanding of the neuronal circuitry underlying neurogenic neuroprotection may contribute to improving neurological outcomes in ischemic brain insults.

Intrinsic neurons of fastigial nucleus mediate neurogenic neuroprotection against excitotoxic and ischemic neuronal injury in rat

Electrical stimulation of the cerebellar fastigial nucleus (FN) elevates regional cerebral blood flow (rCBF) and arterial pressure (AP) and provides long-lasting protection against focal and global ischemic infarctions. We investigated which neuronal element in FN, perikarya or axons, mediates this central neurogenic neuroprotection and whether it also protects against excitotoxicity. In anesthetized rats, the FN was stimulated for 1 hr, and ibotenic acid (IBO) was microinjected unilaterally into the striatum. In unstimulated controls, the excitotoxic lesions averaged approximately 40 mm3. Stimulation of FN, but not dentate nucleus (DN), significantly reduced lesion volumes up to 80% when IBO was injected 15 min, 72 hr, or 10 d, but not 30 d, thereafter. In other rats, intrinsic neurons of FN or DN were destroyed by pretreatment with IBO. Five days later, the FN was stimulated, and 72 hr later, IBO was microinjected into the striatum. Lesions of FN, but not DN, abolished neuroprotection but not the elevations of rCBF and AP elicited from FN stimulation. Excitotoxic lesions of FN, but not DN, also abolished the 37% reduction in focal ischemic infarctions produced by middle cerebral artery occlusion. Excitation of intrinsic FN neurons provides long-lasting, substantial, and reversible protection of central neurons from excitotoxicity, as well as focal ischemia, whereas axons in the nucleus, probably collaterals of ramified brainstem neurons, mediate the elevations in rCBF, which do not contribute to neuroprotection. Long-lived protection against a range of injuries is an unrecognized function of FN neurons transmitted over pathways distinct from those regulating rCBF.

Evidence for higher functions of the cerebellum: eating and grooming elicited by cerebellar stimulation in cats

Well-organized eating and grooming behaviors were elicited in cats by stimulation of a zone in the cerebellum that extended from the fastigial nucleus to the superior cerebellar peduncle. Behaviors appeared to result from the facilitation of specific sensorimotor mechanisms, rather than the induction of generalized "drive" states. The results emphasize the need for a broad view of cerebellar function.