Direct Enhancement Effect of Hippocampal Cholinergic Neurostimulating Peptide on Cholinergic Activity in the Hippocampus

The cholinergic efferent network from the medial septal nucleus to the hippocampus is crucial for learning and memory. This study aimed to clarify whether hippocampal cholinergic neurostimulating peptide (HCNP) has a rescue function in the cholinergic dysfunction of HCNP precursor protein (HCNP-pp) conditional knockout (cKO). Chemically synthesized HCNP or a vehicle were continuously administered into the cerebral ventricle of HCNP-pp cKO mice and littermate floxed (control) mice for two weeks via osmotic pumps. We immunohistochemically measured the cholinergic axon volume in the stratum oriens and functionally evaluated the local field potential in the CA1. Furthermore, choline acetyltransferase (ChAT) and nerve growth factor (NGF) receptor (TrkA and p75NTR) abundances were quantified in wild-type (WT) mice administered HCNP or the vehicle. As a result, HCNP administration morphologically increased the cholinergic axonal volume and electrophysiological theta power in HCNP-pp cKO and control mice. Following the administration of HCNP to WT mice, TrkA and p75NTR levels also decreased significantly. These data suggest that extrinsic HCNP may compensate for the reduced cholinergic axonal volume and theta power in HCNP-pp cKO mice. HCNP may function complementarily to NGF in the cholinergic network in vivo. HCNP may represent a therapeutic candidate for neurological diseases with cholinergic dysfunction, e.g., Alzheimer's disease and Lewy body dementia.

Reduction of glutamatergic activity through cholinergic dysfunction in the hippocampus of hippocampal cholinergic neurostimulating peptide precursor protein knockout mice

Cholinergic activation can enhance glutamatergic activity in the hippocampus under pathologic conditions, such as Alzheimer's disease. The aim of the present study was to elucidate the relationship between glutamatergic neural functional decline and cholinergic neural dysfunction in the hippocampus. We report the importance of hippocampal cholinergic neurostimulating peptide (HCNP) in inducing acetylcholine synthesis in the medial septal nucleus. Here, we demonstrate that HCNP-precursor protein (pp) knockout (KO) mice electrophysiologically presented with glutamatergic dysfunction in the hippocampus with age. The impairment of cholinergic function via a decrease in vesicular acetylcholine transporter in the pre-synapse with reactive upregulation of the muscarinic M1 receptor may be partly involved in glutamatergic dysfunction in the hippocampus of HCNP-pp KO mice. The results, in combination with our previous reports that show the reduction of hippocampal theta power through a decrease of a region-specific choline acetyltransferase in the stratum oriens of CA1 and the decrease of acetylcholine concentration in the hippocampus, may indicate the defined cholinergic dysfunction in HCNP-pp KO mice. This may also support that HCNP-pp KO mice are appropriate genetic models for cholinergic functional impairment in septo-hippocampal interactions. Therefore, according to the cholinergic hypothesis, the model mice might are potential partial pathological animal models for Alzheimer's disease.

Enhancement of long-term potentiation via muscarinic modulation in the hippocampus of HCNP precursor transgenic mice

Hippocampal cholinergic neurostimulating peptide (HCNP) regulates acetylcholine synthesis in the septal hippocampus through the quantitative increase of choline acetyltransferase levels in the septal nucleus both in vitro and in vivo. Additionally, HCNP-precursor protein transgenic (HCNP-pp Tg) mice display depressive behavior. To examine the physiological function of HCNP and/or HCNP-pp on hippocampal neural activity, we investigated whether overexpression of HCNP-pp strengthened the efficiency of neural activity in the hippocampus. Long-term potentiation (LTP) of excitatory synaptic transmission was induced by a tetanic stimulation of the Schaffer collateral-commissural fibers (SCs) in mouse hippocampal slices. LTP in HCNP-pp Tg mice was significantly enhanced when compared with wild-type littermate (WT) mice. This facilitation of LTP in HCNP-pp Tg mice was blocked by atropine or pirenzepine, but not by mecamylamine. In contrast, LTP in WT mice was not affected by atropine, but enhanced by carbachol. However, neither difference in the input-output relationship of field excitatory postsynaptic potentials nor in the facilitation ratio in paired-pulse stimulation of the SCs was observed between HCNP-pp Tg and WT mice, indicating that presynaptic glutamate release in HCNP-pp Tg mice is similar to that of WT mice. These results suggest that muscarinic (M1) modulation of glutamatergic postsynaptic function may be involved in strengthening LTP in HCNP-pp Tg mice.

Differences in dopaminergic modulation to motor cortical plasticity between Parkinson's disease and multiple system atrophy

Dopamine modulates the synaptic plasticity in the primary motor cortex (M1). To evaluate whether the functioning of the cortico-striatal circuit is necessary for this modulation, we applied a paired associative stimulation (PAS) protocol that comprised an electric stimulus to the right median nerve at the wrist and subsequent transcranial magnetic stimulation of the left M1, to 10 patients with Parkinson's disease (PD) and 10 with multiple system atrophy of the parkinsonian type (MSA-P) with and without dopamine replacement therapy (-on/off). To investigate the M1 function, motor-evoked potentials (MEPs) were measured before and after the PAS. In both patient groups without medication, the PAS protocol failed to increase the averaged amplitude of MEPs. The dopamine replacement therapy in PD, but not in MSA-P effectively restored the PAS-induced MEP increase. This suggests that not the existence of dopamine itself but the activation of cortico-striatal circuit might play an important role for cortical plasticity in the human M1.

Overlapping connections within the motor cortico-basal ganglia circuit: fMRI-tractography analysis

Contribution of the subcortical nuclei to the coordination of human behavior is dependent on the existence of appropriate anatomical architecture. Interpretations of available data have led to opposing 'information funneling' and 'parallel processing' hypotheses. Using motor circuit as a model, we examined whether cortico-subcortical circuits, especially cortico-basal ganglia circuits, are funneled or parallel in the control of volitional movement. Twenty-five healthy subjects underwent functional magnetic resonance imaging (fMRI). Activated clusters during self-initiated, sequential finger-to-thumb opposition movements of the left hand were identified in the bilateral supplementary motor area (SMA), right lateral premotor cortex (PM) and primary motor cortex (M1), and in the right striatum and thalamus. These functionally defined clusters were applied to probabilistic tractography based on diffusion-weighted MRI to examine patterns of connectivity. Striatal and thalamic sub-regions with high probabilities of connection to the motor cortices partially overlapped, with connection to the two premotor areas outspreading rostrally relative to M1. We suggest that, on a macroscopic anatomical level, there is overlap as well as segregation among connections of the motor cortices with the striatum and thalamus. This supports the notion that neuronal information of the motor cortices is funneled, and parallel processing is not an exclusive principle in the basal ganglia.

Phosphorylation of collapsin response mediator protein-2 regulates its localization and association with hippocampal cholinergic neurostimulating peptide precursor in the hippocampus

Hippocampal cholinergic neurostimulating peptide (HCNP) induces the synthesis of acetylcholine in the medial septal nucleus in vitro and in vivo. The precursor, HCNP-pp, is a multifunctional protein participating in important signaling pathways, such as MAPK/ERK kinase (MEK) and G-protein-coupled receptor kinase 2 (GRK2). We recently demonstrated that HCNP-pp colocalizes with collapsin response mediator protein-2 (CRMP-2) at presynaptic terminals in the hippocampus, suggesting that HCNP-pp may play an important role in presynaptic function in association with CRMP-2. To clarify the involvement of phosphorylation in regulating the interaction between HCNP-pp and CRMP-2, we investigated the colocalization of HCNP-pp with unphosphorylated- and/or phosphorylated-CRMP-2 (pCRMP-2) at presynaptic terminals. We further determined if the phosphorylation of CRMP-2 affects the binding between those proteins. Here, we demonstrate that HCNP-pp predominantly colocalizes and associates with unphosphorylated and/or pSer-522-CRMP-2 at presynaptic terminals in the hippocampus. Interestingly, HCNP-pp does not associate with pThr-509/514-CRMP-2, which is primarily localized at postsynaptic terminals. These findings suggest that HCNP-pp, in association with unphosphorylated and/or pSer522-CRMP-2, plays an important role in presynaptic function in the mature hippocampus.

Co-localization of hippocampal cholinergic neurostimulating peptide precursor with collapsin response mediator protein-2 at presynaptic terminals in hippocampus

Hippocampal cholinergic neurostimulating peptide (HCNP) induces the synthesis of acetylcholine in medial septal nucleus in vitro and in vivo. HCNP precursor protein (HCNP-pp) is a multifunctional protein that participates in a number of signaling pathways, including MAPK/extracellular signal and G-protein-coupled receptor kinase 2. We recently demonstrated that the amount of collapsin response mediator protein-2 (CRMP-2) is increased in hippocampus of HCNP-pp transgenic mice. To clarify the interaction between HCNP/HCNP-pp and CRMP-2 and its role in synaptic function, we investigated whether HCNP-pp is localized to the synapse and if it affects protein expression. Here, we demonstrate that HCNP-pp co-localizes with CRMP-2 at presynaptic terminals. Furthermore, HCNP-pp overexpression increases synaptophysin levels. These findings suggest that HCNP-pp, in association with CRMP-2, plays an important role in presynaptic function in the hippocampus.

Suppression of astrocyte lineage in adult hippocampal progenitor cells expressing hippocampal cholinergic neurostimulating Peptide precursor in an in vivo ischemic model

Hippocampal cholinergic neurostimulating peptide (HCNP) is known to promote differentiation of septohippocampal cholinergic neurons. The HCNP precursor protein (HCNP-pp) may play several roles, for example, as an ATP-binding protein, a Raf kinase inhibitor protein, and a phosphatidylethanolamine-binding protein, as well as a precursor for HCNP. This study therefore aimed to elucidate the involvement of HCNP-pp in specific neural lineages after stroke using a hypoxic-ischemic (HI) rat model of brain ischemia. The specific neural lineages in the hippocampus were investigated 14 days after ischemia. Some bromodeoxyuridine (BrdU)(+) neural progenitor cells in the hippocampus of hypoxic, HI, or sham-operated rats expressed HCNP-pp. Almost half of the BrdU(+)/HCNP-pp(+) cells also expressed the oligodendrocyte lineage marker 2',3'-cyclic nucleotide 3'-phosphodiesterase, whereas only a few BrdU(+)/HCNP-pp(+) cells in the hippocampus in HI brains expressed the neuronal lineage marker, doublecortin (DCX). Interestingly, no BrdU(+)/HCNP-pp(+) progenitor cells in hypoxic, HI, or sham-operated brains expressed the astrocyte lineage marker, glial fibrillary acidic protein. Together with previous in vitro data, the results of this study suggest that the expression level of HCNP-pp regulates the differentiation of neural progenitor cells into specific neural lineages in the HI hippocampus, indicating that neural stem cell fate can be controlled via the HCNP-pp mediating pathway.

Changes in striatal dopamine release associated with human motor-skill acquisition

The acquisition of new motor skills is essential throughout daily life and involves the processes of learning new motor sequence and encoding elementary aspects of new movement. Although previous animal studies have suggested a functional importance for striatal dopamine release in the learning of new motor sequence, its role in encoding elementary aspects of new movement has not yet been investigated. To elucidate this, we investigated changes in striatal dopamine levels during initial skill-training (Day 1) compared with acquired conditions (Day 2) using ¹¹C-raclopride positron-emission tomography. Ten volunteers learned to perform brisk contractions using their non-dominant left thumbs with the aid of visual feedback. On Day 1, the mean acceleration of each session was improved through repeated training sessions until performance neared asymptotic levels, while improved motor performance was retained from the beginning on Day 2. The ¹¹C-raclopride binding potential (BP) in the right putamen was reduced during initial skill-training compared with under acquired conditions. Moreover, voxel-wise analysis revealed that ¹¹C-raclopride BP was particularly reduced in the right antero-dorsal to the lateral part of the putamen. Based on findings from previous fMRI studies that show a gradual shift of activation within the striatum during the initial processing of motor learning, striatal dopamine may play a role in the dynamic cortico-striatal activation during encoding of new motor memory in skill acquisition.

Plaque vulnerability in internal carotid arteries with positive remodeling

BACKGROUND

This study aimed to evaluate the efficacy of assessing positive remodeling for predicting future stroke events in the internal carotid artery. We therefore assessed narrowing of the carotid artery lumen using multidetector-row computer tomography (MDCT) angiography and carotid plaque characteristics using black-blood (BB) magnetic resonance (MR).

METHODS

We retrospectively selected 17 symptomatic and 11 asymptomatic lesions with luminal narrowing >50%. We compared remodeling parameters of luminal stenosis (remodeling ratio, RR/remodeling index, RI) using MDCT and MR intensities of atherosclerotic plaque contents using the BB technique (relative signal intensity, rSI). We also confirmed the validity of the relationship between MR intensity and atherosclerotic plaque contents by histology. The levels of biological markers related to vessel atherosclerosis were measured.

RESULTS

Plaque lesions with positive remodeling in carotid arteries were associated with a significantly higher prevalence of stroke compared with plaques with negative remodeling (p < 0.05). Radiologic and histologic analyses determined that plaques with positive remodeling had higher signal intensities (with respect to their lipid-rich content or to hemorrhage) compared with negative remodeling (correlation coefficients: RI and rSI, r = 0.41, p < 0.05; RR and rSI, r = 0.50, p < 0.05). Levels of biological markers, including high-sensitivity C-reactive protein, hemoglobin A1C, total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol, were not useful for predicting stroke events.

CONCLUSIONS

The results of this study suggest that the combined analysis of RR, RI and rSI could potentially help to predict future stroke events.

Reversible cerebral vasoconstriction syndrome in a patient with Takayasu's arteritis

We herein present the first reported case of reversible cerebral vasoconstriction syndrome (RCVS) in Takayasu's arteritis (TA), in a patient with severe thunderclap headache and generalized tonic-clonic seizure. Magnetic resonance imaging and angiography revealed posterior reversible encephalopathy syndrome, followed by severe vasoconstriction in multiple arteries. RCVS should be included in the differential diagnosis of thunderclap headache attacks with radiologic intracranial vascular abnormalities in connective tissue diseases, including TA.

Suppressed phosphorylation of collapsin response mediator protein-2 in the hippocampus of HCNP precursor transgenic mice

We previously reported a novel peptide, Hippocampal Cholinergic Neurostimulating Peptide (HCNP), which induces acetylcholine synthesis by increasing the amount of choline acetyltransferase (ChAT) in medial septal nuclei. The HCNP precursor protein (HCNP-pp), composed of 186 amino acids, is an inhibitory factor of the c-Raf/MEK cascade and may be involved in fetal rat brain development via the inhibition of phosphorylation of Erk. To clarify the involvement of HCNP in hippocampal cholinergic circuitry, we previously generated HCNP-pp transgenic (HCNP-pp Tg) mice using the promoter of the α subunit of Ca(2+) calmodulin-dependent protein kinase II (CaMKIIα). These mice showed increased levels of ChAT in medial septal nuclei at 12 weeks of age, and the phenotype of depressive mood at 30 weeks of age. Here, through proteomic analysis we investigated the alteration of protein expression in the hippocampus of HCNP-pp Tg mice compared with wild-type littermate mice. We demonstrate that the activation of collapsin response mediator protein-2 (CRMP-2) is increased in the transgenic mice at 12 weeks of age when compared with wild-type littermate mice.

[Lambert-Eaton myasthenic syndrome associated with pulmonary squamous cell carcinoma and circulating anti-P/Q-type voltage-gated calcium channel antibody]

We report a 64-year-old man diagnosed with Lambert-Eaton myasthenic syndrome (LEMS) associated with pulmonary squamous cell carcinoma. Circulating anti-P/Q-type voltage-gated calcium channel (VGCC) antibody was detected, and the patient was treated with 3,4-diaminopyridine. At age 61, chest radiograph revealed a tumor shadow in the right upper lung field. This was surgically removed, and a histological diagnosis of moderately differentiated pulmonary squamous cell carcinoma was obtained. After about 1 year, mediastinal metastasis was detected and 5-FU was administered. Eight months later, metastasis was noted in the left frontal hemisphere, and radiosurgical therapy was performed. The brain tumor gradually shrank but generalized fatigue, thirst, and gait disturbance developed after 4 months. A diagnosis of LEMS was made on the basis of neurological findings including proximal muscle weakness and absent tendon reflexes; autonomic symptoms (thirst, constipation, and impotence); characteristic electromyographic findings; and circulating anti-P/Q-type VGCC antibody. He has been treated with 3,4-diaminopyridine at a dose of 30 mg/day, resulting in marked improvement in symptoms but little change in electromyographic findings. The present case is very rare and suggests that anti-P/Q-type VGCC antibody may be involved in the mechanism of LEMS associated with pulmonary squamous cell carcinoma.

Overexpression of hippocampal cholinergic neurostimulating peptide in heterozygous transgenic mice increases the amount of ChAT in the medial septal nucleus

Acetylcholine modulates neural activity in the hippocampal glutamatergic pathway via the induction of phosphorylated Erk and may act as a novel transmitter in septohippocampal memory formation. However, how acetylcholine synthesis in the septal nucleus is regulated is unknown. We have purified a peptide from the hippocampus of the young adult rat, named hippocampal cholinergic neurostimulating peptide (HCNP) that induces acetylcholine synthesis in vitro in the septal nucleus. Previously, levels of this peptide and/or precursor protein were reported to be decreased, and the protein to be nitrated in the brains of patients with Alzheimer's disease. Here, to clarify the involvement in the regulation of acetylcholine synthesis in vivo in the medial septal nucleus, we generated HCNP precursor transgenic mice, using a Ca2+ calmodulin-dependent protein kinase II genomic promoter. The amount of cholineacetyltransferase (ChAT) in the medial septal nucleus was increased in heterozygous HCNP transgenic mice, compared with non-transgenic littermates. This result suggests that HCNP is involved in regulating acetylcholine synthesis in vivo in the medial septal nucleus and, as such, is important for memory function.

Therapeutic targets and limits of minocycline neuroprotection in experimental ischemic stroke

BACKGROUND

Minocycline, a second-generation tetracycline with anti-inflammatory and anti-apoptotic properties, has been shown to promote therapeutic benefits in experimental stroke. However, equally compelling evidence demonstrates that the drug exerts variable and even detrimental effects in many neurological disease models. Assessment of the mechanism underlying minocycline neuroprotection should clarify the drug's clinical value in acute stroke setting.

RESULTS

Here, we demonstrate that minocycline attenuates both in vitro (oxygen glucose deprivation) and in vivo (middle cerebral artery occlusion) experimentally induced ischemic deficits by direct inhibition of apoptotic-like neuronal cell death involving the anti-apoptotic Bcl-2/cytochrome c pathway. Such anti-apoptotic effect of minocycline is seen in neurons, but not apparent in astrocytes. Our data further indicate that the neuroprotection is dose-dependent, in that only low dose minocycline inhibits neuronal cell death cascades at the acute stroke phase, whereas the high dose exacerbates the ischemic injury.

CONCLUSION

The present study advises our community to proceed with caution to use the minimally invasive intravenous delivery of low dose minocycline in order to afford neuroprotection that is safe for stroke.

Predicting the motor outcome of acute disseminated encephalomyelitis by apparent diffusion coefficient imaging: Two case reports

We present two cases of young adults with acute disseminated encephalomyelitis (ADEM) who developed severe conscious and motor disturbances. Despite their similar initial clinical course and MRI findings, their motor function outcomes were quite different. In both cases, fluid attenuated inversion recovery (FLAIR) sequenced MRI showed multiple symmetric hyperintense lesions in the internal capsule and the brainstem at the subacute stage. However, in case 1 the apparent diffusion coefficient (ADC) was pathologically decreased in the internal capsule, whereas the ADC for case 2 was normal. At the end of the examination period, severe motor disability (bedridden state) with brain atrophy apparent on MRI remained in case 1, whereas case 2 made an almost full recovery without brain atrophy. These two cases suggest that altered ADC in the internal capsules at the subacute stage may reflect a different pathogenesis between cytotoxic and vasogenic edema, and may be a valuable indicator for the prognosis of motor disturbance.

[Case of paraneoplastic limbic encephalitis associated with malignant B cell lymphoma]

We report a case of a 62-year-old man with limbic encephalitis associated with diffuse large B cell lymphoma. He was hospitalized for the assessment of cognitive disturbance and changes in characteristics. Neurological examination revealed disturbance of recall and recent memory. Magnetic resonance (MR) imaging of the brain revealed bilateral atrophy of the medial temporal lobes. Cerebrospinal fluid (CSF) examination revealed mononuclear pleocytosis and elevated protein levels. Herpes simplex virus DNA was not detected in the CSF by the polymerase chain reaction. Immunological investigation of the patient's serum samples showed no evidence of acute infection with herpes simplex virus or cytomegalovirus. Chest computed tomography (CT) revealed a mass lesion on the right hilum of the lung. Therefore, tumor resection was performed. The pathological diagnosis was diffuse large B cell lymphoma. We diagnosed this patient with paraneoplastic limbic encephalitis. Chemotherapy was performed, but the patient's clinical symptoms failed to improve. We investigated 7 previously reported cases of paraneoplastic limbic encephalitis associated with malignant lymphoma in Japan. We suggest that an early diagnosis of paraneoplastic limbic encephalitis with progressive symptoms such as changes in characteristics is important. Early diagnosis and treatment of malignant tumors is desirable to facilitate clinical recovery and improve prognosis.

Intramedullary hemorrhage caused by arteriovenous malformation: a case of mixed lateral and medial medullary syndrome

A 48-year-old man with no known risk factor for cerebrovascular disease, other than cigarette smoking, experienced the sudden onset of a mixed lateral and medial medullary syndrome. Computed tomography scan failed to show any definite abnormality. Magnetic resonance imaging scans revealed hemorrhage restricted to the left dorsolateral medulla. Angiography showed abnormal arteries originating from the left vertebral artery with small niduses located on the surface of the medulla and contralateral cerebellum. Small brain-stem hemorrhages are a contraindication to thrombolytic or anticoagulant therapy, and therefore must be recognized in the acute stage.

[A case of neurolymphomatosis diagnosed with FDG-PET]

A 38-year-old man with non-Hodgkin's lymphoma presented with hypesthesia and muscle weakness in the left upper limb. A lack of F-waves in left median and ulnar nerve conduction studies suggested a lesion at the proximal segments of the peripheral nerves, such as the left brachial plexus or nerve roots. Cervical magnetic resonance imaging revealed no lesions compressing nerve roots or peripheral nerves. Small and obscure uptake on the left side of the cervical nerve roots on 67Ga-scintigraphy was indistinguishable from artifact. Positron emission tomography-computed tomography (PET/CT) revealed a region of high glucose uptake in a left cervical intervertebral foramen, leading to a diagnosis of neurolymphomatosis. Neurological symptoms improved following additional chemotherapy, and the high glucose-uptake lesion disappeared. FDG-PET/CT is useful for rapid and non-invasive evaluation of neurolymphomatosis.

Differential expression of HCNP-related antigens in hippocampus in senescence-accelerated mice

Hippocampal cholinergic neurostimulating peptide (HCNP), originally isolated from soluble fraction of young rat hippocampus and released from hippocampus by the stimulation of N-methyl-d-aspartate (NMDA) receptors, enhances the cholinergic phenotype development in vitro. HCNP precursor protein (HCNP-pp) has multiple functions, not only acting as the precursor of HCNP but also serving as an inhibitor of phosphorylation of Erk and contributing to neuronal growth and memory formation. In this study, the accumulation of HCNP and/or HCNP precursor in hippocampus was found to progress from 2 to 5 months of age in senescence-accelerated mouse-prone 8 (SAM P8). This HCNP surge in the hippocampus appears to correspond to the age of onset of memory deterioration, reduction of amount of NMDA-type receptor, and morphological aberration in this dementia model mouse, SAM P8. The present findings, together with our previously published results, suggest that the HCNP and/or HCNP precursor is involved in the dysfunction of the cholinergic neuronal system and memory deterioration in this model mouse via NMDA-type receptor signaling and the activation of the MAP cascade.

Early changes in KCC2 phosphorylation in response to neuronal stress result in functional downregulation

The K+ Cl- cotransporter KCC2 plays an important role in chloride homeostasis and in neuronal responses mediated by ionotropic GABA and glycine receptors. The expression levels of KCC2 in neurons determine whether neurotransmitter responses are inhibitory or excitatory. KCC2 expression is decreased in developing neurons, as well as in response to various models of neuronal injury and epilepsy. We investigated whether there is also direct modulation of KCC2 activity by changes in phosphorylation during such neuronal stressors. We examined tyrosine phosphorylation of KCC2 in rat hippocampal neurons under different conditions of in vitro neuronal stress and the functional consequences of changes in tyrosine phosphorylation. Oxidative stress (H2O2) and the induction of seizure activity (BDNF) and hyperexcitability (0 Mg2+) resulted in a rapid dephosphorylation of KCC2 that preceded the decreases in KCC2 protein or mRNA expression. Dephosphorylation of KCC2 is correlated with a reduction of transport activity and a decrease in [Cl-]i, as well as a reduction in KCC2 surface expression. Manipulation of KCC2 tyrosine phosphorylation resulted in altered neuronal viability in response to in vitro oxidative stress. During continued neuronal stress, a second phase of functional KCC2 downregulation occurs that corresponds to decreases in KCC2 protein expression levels. We propose that neuronal stress induces a rapid loss of tyrosine phosphorylation of KCC2 that results in translocation of the protein and functional loss of transport activity. Additional understanding of the mechanisms involved may provide means for manipulating the extent of irreversible injury resulting from different neuronal stressors.

Recurrent limbic and extralimbic encephalitis associated with thymoma

A 33-year-old woman, with a 7-year clinical history of invasive thymoma treated at ages 26 and 30 years by thymectomy and radiation, presented with a generalized convulsion and loss of consciousness. Following the seizure there was no neurological deficit and normal tendon reflexes. Magnetic resonance imaging (MRI) of the brain without gadolinium enhancement revealed multiple small lesions of high signal intensity on T2 and diffusion weighted images located in the cortical area beyond the temporal lobes. Brain biopsy demonstrated encephalitis with activated microglias and activated T-cell infiltration. Within 4 months of treatment with nothing other than anticonvulsant therapy, the lesions visible on the original MRI had completely disappeared and the patient was discharged with no neurological symptoms. The patient subsequently had two more episodes with a variety of symptoms such as incontinence, confusion, aphasia, apallial syndrome, and motor paresis. MRI following these episodes again revealed multiple lesions of similar appearance to those of the first episode, although in different locations, and much larger and more numerous. The patient had steroid pulse therapy after both episodes and the lesions noted on brain MRI disappeared within a few months with minimal neurological complications.

[Function of HCNP/HCNP precursor in memory formation]

Based on the hypothesis of target-derived trophic factor, we have purified a novel peptide from young rat hippocampus, named Hippocampal Cholinergic Neurostimulating Peptide: HCNP, which induces the synthesis of acetylcholine in the medial septal nucleus. This peptide is aligned with the N terminal of protein composed 186 amino acids (HCNP precursor protein), and released from neurons in hippocampus by the NMDA receptor stimulation. Moreover, HCNP precursor can be involved in neural activity in hippocampus via the inhibition of phosphorylation of Erk. HCNP and its precursor can be a candidate for the key molecules elucidating the underlying association among Abeta, phosphorylated tau, degeneration of dendritic spine and decrease of acetylcholine in Alzheimer brain.

[An adult case of cyclic vomiting syndrome in which tricyclic antidepressant was effective]

A 30-year-old man presented with a 10-year history of recurrent, stereotypic episodes of incapacitating nausea and vomiting. Initially, he had been diagnosed as having superior mesenteric artery syndrome, and had undergone abdominal surgery at age 20. The patient was in good health between episodes. During each episode, oral intake was impossible and total parenteral nutrition and sedation were necessary. Conventional antiemetics such as metoclopramide were not effective, and the 5-HT3 antagonist ondansetron hydrochloride was only partially effective. Investigations into gastrointestinal, hormonal, and metabolic function were unremarkable, as was psychiatric evaluation. Diagnosing this to be an adult case of cyclic vomiting syndrome, we administered amitriptyline hydrochloride; a prophylactic agent for migraine. This resulted in rapid resolution of the episodes, which have not recurred over several years' follow up. Recently, cyclic vomiting syndrome has been considered a subtype of migraine. In the present case, effectiveness of the tricyclic antidepressant amitriptyline hydrochloride indicated that migraine and cyclic vomiting syndrome have a common pathology. Clinicians should be aware that cyclic vomiting syndrome can affect adults as well as children, and that treatment for migraine may be effective.

Pituitary adenylate cyclase-activating polypeptide (PACAP) ameliorates experimental autoimmune encephalomyelitis by suppressing the functions of antigen presenting cells

Pituitary adenylate cyclase-activating polypeptide (PACAP), a 38-amino acid neuropeptide belonging to the secretin-glucagon-vasoactive intestinal peptide (VIP) family, performs a variety of functions in both the nervous and immune systems. In this study, we examined the effects of PACAP on experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mice. When administrated intraperitoneally every other day after immunization with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55, PACAP ameliorated both the clinical and pathological manifestations of EAE Ex vivo examination revealed a significant inhibition of MOG35-55-specific Th1 response in mice treated with PACAP. In vitro analysis revealed that PACAP suppressed the production of inflammatory cytokines, including TNF-alpha, IL-1beta, and IL-12, and expression of the costimulatory factor B7-2 on macrophage and microglia, which may function as antigen presenting cells (APC) in the CNS. While PACAP suppressed the differentiation of MOG35-55-specific T cells into Th1 effectors upon restimulation with MOG35-55-expressing APC, it did not affect interferon (IFN)-gamma production by MOG35-55-specific T cells stimulated with anti-CD3 and anti-CD28. These observations suggested that PACAP suppressed induction of EAE primarily via suppression of APC function and inflammatory cytokine production. PACAP may be useful in the future treatment of Th1-mediated autoimmune diseases, such as multiple sclerosis.

Cognitive Event-Related Potentials: Useful Clinical Information in Alzheimers Disease

Cognitive event-related potentials (ERPs) have been used as a marker of cognitive function in patients with psychiatric and neurological disorders. In particular, the P300 potential has been widely utilized to study dementia and aging, because the P300 ERP component is easily observed and reflects attention and memory processing. However, the relationship between parameters of the P300 potential and the severity or type of cognitive impairment in patients with Alzheimer's disease (AD) remains controversial. Because specific and effective anti-dementia treatments have recently become available for AD, more useful information is needed about the clinical aspects of this disease, including methods of making an accurate and early diagnosis, differentiation from vascular dementia and other degenerative dementias, assessment of severity, assessment of disease progression, evaluation of the response to treatment, and prediction of the prognosis. This mini-review described new discoveries on recent clinical application of ERPs in AD with respect to the above-mentioned areas. Although the definition of normal ERP values and the most appropriate method of ERP recording in AD patients have not been well defined, recent findings suggest that ERP analysis may be a clinically useful, inexpensive, noninvasive, and reliable method of assessing AD.

Brain Malformations Caused by Retroviral Vector-Mediated Gene Transfer of Hippocampal Cholinergic Neurostimulating Peptide Precursor Protein into the CNS via Embryonic Mice Ventricles

Hippocampal cholinergic neurostimulating peptide precursor protein (HCNP-pp) is a unique multifunctional protein, being not only the precursor of HCNP, which promotes the phenotype development of septo-hippocampal cholinergic neurons, but also the binding protein of phosphatidylethanolamine, ATP, Raf-1 kinase (known as "Raf-1 kinase inhibitory factor" in peripheral organs), and serine protease. We obtained a high-titer retroviral vector harboring HCNP-pp cDNA by the use of a modified packaging cell line and centrifugation, and by injecting it into embryonic mouse ventricles, we investigated the function of its gene product within the central nervous system (CNS). We found that efficient transduction into hippocampal pyramidal neurons can be achieved by injecting the vector into embryonic brain ventricles on embryonic day 14 (E14). Three days after receiving the intraventricular injection of the high-titer HCNP-pp retrovirus vector on E14, the tissues around the ventricles showed an overexpression of HCNP-pp. This was accompanied by a reduced amount of activated MEK and Erk (as analyzed by histochemical and Western blot methods), suggesting that HCNP-pp also regulates the MAP-kinase cascade within the CNS. Surprisingly, mouse brains that received the HCNP-pp retroviral vector showed massive malformation of the hippocampus and cerebellum when examined 30 days after birth. This shows that strictly regulated HCNP-pp gene expression is necessary for the normal development of the mouse brain, and that the moderate overexpression achieved by retroviral vector-mediated gene transfer is sufficient to cause severe abnormality of entire brain structures.

Distribution of astrocytic plaques in the corticobasal degeneration brain and comparison with tuft-shaped astrocytes in the progressive supranuclear palsy brain

Corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) have some clinical and pathological features in common. Each, however, has been shown to have specific astrocytic inclusions. CBD is characterized by astrocytic plaques, and PSP is characterized by tuft-shaped astrocytes. To clarify differences between these inclusions, we investigated intracerebral distribution of astrocytic plaques and tuft-shaped astrocytes in autopsied brains of patients with either CBD or PSP. Specimens from ten patients with CBD and five patients with PSP were stained by the Gallyas-Braak method. Densities of the astrocytic plaques and tuft-shaped astrocytes were determined for 11 cerebral cortical regions, 6 subcortical nuclei, 5 brain stem regions, the cerebellar cortex and the dentate nucleus. Astrocytic plaques were most abundant in the prefrontal and premotor areas in the cerebral cortex of CBD brains, whereas tuft-shaped astrocytes were most prominent in the precentral gyrus and premotor area of PSP brains. Many astrocytic plaques were observed in the caudate nucleus of CBD brains, whereas tuft-shaped astrocytes were abundant in both the caudate and putamen and moderate in number in the globus pallidus, subthalamic nucleus and thalamus in PSP brains. Very slight accumulation of astrocytic plaques was seen in the brain stem of CBD brains, whereas numerous tuft-shaped astrocytes were found in the red nucleus and superior colliculus of PSP brains. Distribution of the astrocytic plaques and tuft-shaped astrocytes differed greatly. Thus, CBD and PSP can be considered different entities.

Autonomic dysfunctions in dementia with Lewy bodies

Twenty-nine cases of both clinically and neuropathologically diagnosed dementia with Lewy bodies (DLB) were retrospectively examined for autonomic symptoms. Twenty-eight cases showed some kind of autonomic dysfunction. Urinary incontinence (97 %) and constipation (83 %) were the two most common. Although urinary retention and episodic hypotension causing syncopal attacks were less common, the frequency was still high (28 % each). There were 18 cases (62 %) with severe autonomic failure. These 28 cases showed similar tendencies, with no significant differences between the subtypes of DLB (brainstem, limbic, and neocortical types or common and pure forms). We found that DLB of all pathological subtypes exhibits some kind and level of autonomic symptoms.

Specific binding of 125I-hippocampal cholinergic neurostimulating peptide (HCNP) to rat brain membranes: characterization and regional distribution

An undecapeptide-hippocampal cholinergic neurostimulating peptide (HCNP), originally purified from young rat hippocampus, enhances cholinergic phenotype development in the medial septal nucleus in vitro. To survey and characterize the HCNP receptor within the central nervous system, we used iodinated HCNP as a labeled ligand. In preliminary experiments, [125I]HCNP binding was highest in the crude P2 membrane fraction, so all subsequent experiments were performed using this fraction. The binding was saturable and reversible, and unlabeled ligand inhibited it. Scatchard analysis of the concentration-dependent saturation of binding indicated a single population of non-interacting sites with K(d) 4.0+/-0.7 nM and B(max) 10.7+/-3.8 pmol/mg protein. Dissociation experiments revealed a dissociation constant (K(-1)) of 0.07 min(-1). Inhibition experiments using HCNP and its shorter peptide fragments suggested that the active binding site resided close to the peptide's C-terminal sequence. Since [125I]HCNP binding was found in crude P2 membrane fractions from animals at all ages examined, HCNP may also perform important functional roles in the adult brain. Further, the predominant distribution of the receptor in the P2 membrane fraction, and the similarity in distribution patterns between the binding site and HCNP-precursor protein mRNA expression suggest that the peptide exerts its functions in the vicinity of the dendrites of the neurons that produce it.

Long-term effects of donepezil on P300 auditory event-related potentials in patients with Alzheimer's disease

The P300, one of the cognitive event-related potentials (ERPs) of the cerebral cortex, reflects the functioning of the neurochemical system involved in cognitive processes. We investigated clinical significance of the components of auditory P300 ERPs, in comparison with neuropsychologic tests including the Mini-Mental State Examination and the Japanese version of the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-J cog), for evaluating of the effect of donepezil (DPZ) (5 mg daily for 6 months), an acetylcholinesterase inhibitor, in patients with Alzheimer's disease (AD). Reduction of P300 latency associated with a parallel improvement of ADAS-J cog scores was observed after administration of 5 mg/day of DPZ in patients with AD. P300 latency gives very useful information on the progression of AD, especially in the longitudinal follow-up of patients with AD during treatment with DPZ acting on cholinergic pathways.

[An autopsy case of purulent meningitis, presenting high signals in subarachnoid space and ventricles in diffusion weighted images (DWIs)]

A 79-year-old, bedridden woman with an untreated colon cancer, developed abrupt disturbance of consciousness and high fever. Brain MRI showed significant high signals in the subarachnoid space and ventricles in diffusion-weighted images (DWIs), and she died on the same day. At autopsy, much exudate was found over the base of the brain, leading to a diagnosis of purulent meningitis. On histological findings, inflammatory cell infiltration was significantly restricted within the subarachnoid space, but not into the brain parenchyma. This case report demonstrated that high signals in subarachnoid space and ventricles in DWIs may be very useful for diagnosis of purulent meningitis.

[A case of cavernous sinus cavernous hemangioma presenting with cavernous sinus syndrome]

The authors report an unusual case of a 50-year-old woman presenting with cavernous sinus syndrome, who had a cavernous sinus cavernous hemangioma (CSCH). The acute onset of her symptoms including pain of the right eye, blephaloptosis of the right eye, diplopia, and sensory disturbance of the right face was similar to those of Tolosa-Hunt syndrome. Magnetic resonance imaging and angiography showed a tumor in the right cavernous sinus. Although she showed improvement of the symptoms after receiving oral corticosteroids, follow-up neuroradiological investigations after a year from the onset revealed the mass in the right cavernous sinus which grew up in size. The histopathological findings obtained from the biopsy of the mass demonstrated a CSCH. Our findings suggest that the growth mechanism of CSCH could be progressive ectasia of vessels or their autonomous development at the edges of the lesions.

Decreased expression of hippocampal cholinergic neurostimulating peptide precursor protein mRNA in the hippocampus in Alzheimer disease

Hippocampal cholinergic neurostimulating peptide (HCNP) is involved in the phenotype development of the septo-hippocampal system. HCNP precursor protein (HCNP-pp) is known to interact with other molecules including phosphatidylethanolamine and Raf-1 kinase, and is also known as phosphatidylethanolamine-binding protein and raf kinase-inhibitory protein. To assess whether HCNP-pp is involved in the pathogenesis of Alzheimer disease (AD), the expression levels of its mRNA in the hippocampus of autopsy brains from patients with dementia (including AD and ischemic vascular dementia) were compared with those of non-demented control subjects. The in situ hybridization analysis revealed that the expression of HCNP-pp mRNA in patients with clinically late-onset AD was decreased in the hippocampal CA1 field, but not in the CA3 field or the dentate gyrus. The early-onset AD patients showed a wide range of expression levels in the hippocampal sub-regions. Northern blot analysis of HCNP-pp mRNA in brain tissue supported these observations. Since HCNP is known to stimulate the enzymatic activity of choline acetyltransferase in neurons, its low expression in the CAI field of AD patients may explain the downregulation of cholinergic neurons seen in these patients and may thus contribute to the pathogenic processes underlying AD.

Muscarinic cholinergic and glutamatergic reciprocal regulation of expression of hippocampal cholinergic neurostimulating peptide precursor protein gene in rat hippocampus

Hippocampal cholinergic neurostimulating peptide, an undecapeptide originally isolated from the hippocampus of young rats, enhances acetylcholine synthesis in rat medial septal nucleus in vitro. Hippocampal cholinergic neurostimulating peptide is derived from the N-terminal region of its 21-kmol.wt precursor protein. The highest expression of the hippocampal cholinergic neurostimulating peptide precursor protein messenger RNA is in hippocampal pyramidal neurons. In an in vitro rat hippocampal slice, preparation in which electrical stimulation could be delivered to the Schaffer collateral-CA1 pyramidal cell synapse, semi-quantitative non-radioisotopic in situ hybridization, demonstrated that expression of the hippocampal cholinergic neurostimulating peptide precursor protein messenger RNA is regulated by neuronal activity. Selective inhibition with pharmacological agents revealed that the constitutive hippocampal cholinergic neurostimulating peptide precursor protein messenger RNA level can be up-regulated by D-(-)-2-amino-5-phosphono-valeric acid, and that activity-dependent transcription can be inhibited by tetrodotoxin, nifedipine, 6-cyano-7-nitroquinoxaline-2,3-dione, and scopolamine, but not by mecamylamine. These results indicate that septal cholinergic neurons and hippocampal glutamatergic neurons exert a reciprocal influence over the expression of hippocampal cholinergic neurostimulating peptide precursor protein messenger RNA in the hippocampus, and that the activity-dependent and constitutive expressions of hippocampal cholinergic neurostimulating peptide precursor protein messenger RNA may be regulated by different routes, involving calcium influx via L-type Ca(2+) channels and N-methyl-D-aspartate receptors.

Age-dependent changes in HCNP-related antigen expression in the human hippocampus

Hippocampal cholinergic neurostimulating peptide (HCNP), originally purified from the young rat hippocampus, enhances the cholinergic phenotype development of the medial septal nucleus in vitro. In this study, we examined the HCNP-antigen distribution and the age-related changes in the number of positive cells in the hippocampus (obtained at autopsy from 74 subjects with no known neurological disorders). Immunohistochemical assay revealed that the immunopositive cells were GABAergic neurons and oligodendrocytes. They were first identified in the fetus at around 25 to 30 weeks and their number increased rapidly with advancing postconceptional age to reach maximal at the perinatal stage and in early postnatal life; it then decreased to the adult level by 10 years old. These results suggest that HCNP-related antigen may play important roles in the development and/or differentiation of the human hippocampus.

Hepatitis B virus infection among residents of a nursing home for the elderly: seroepidemiological study and molecular evolutionary analysis

A seroepidemiological study of HBV infection was carried out to investigate the seroprevalence of hepatitis B surface antigen (HBsAg) and the transmission routes of hepatitis B virus (HBV) infection among residents of a nursing home for the elderly. HBV serum markers were examined in 119 residents and 71 healthcare workers in the institution, as also in 1330 healthy subjects from the same geographical area, as the control group. HBsAg was detected in 6 (5%), 0 and 20 (1.5%) residents, healthcare workers and healthy subjects, respectively. Four residents (A-D) who had HBV-DNA in the serum were studied by molecular evolutionary analysis. The strains derived from residents A, B and D were clustered together within a close range of evolutionary distances. Residents B and D, who were not positive for HBsAg at the time of admission to the institution, subsequently became HBsAg-positive asymptomatic carriers. These results suggested intrainstitutional transmission of HBV in the nursing home for the elderly, and confirmed that the source of transmission of HBV to residents B and D was resident A who was positive for HBsAg. Residents in a nursing home for the elderly should be considered as being a high-risk group for HBV infection, and vaccination against HBV of these groups is recommended.

[A case of sarcoid meningoencephalitis with an isolated supratentorial lesion]

A rare case of sarcoid meningoencephalitis with no systemic lesion is reported here. A 58-year old man was admitted experiencing dull headache and speech disturbance. He had never received a diagnosis of systemic sarcoidosis. On admission, neurological examination revealed dysarthria, a defect of the right-side visual field and accelerated right Achilles tendon reflex. A T2-weighted MRI showed a high-intensity signal in the white matter of the left parieto-occipital lobe surrounded by severe brain edema with a mass effect. The meninges around the lesion were enhanced by gadolinium, but no enhancement was observed in the basal portion. Angiotensin-converting enzyme (ACE) activities of cerebrospinal fluid (CSF) and serum were within normal range. The level of interleukin-6 in the CSF was slightly elevated. Chest X ray films and chest CT revealed no abnormal lesions. Whole body gallium scanning showed a hot region only in the intracranial lesion. A brain biopsy was performed. Histological examination revealed typical granuloma of sarcoidosis accompanied by microvasculitis and epithelioid cell granuloma without caseous necrosis. Oral administration of prednisolone improved all symptoms and MRI findings. These observations suggest that release of cytokines from macrophages and epithelioid cells, as well as disruption of the blood-brain barrier due to microvasculitis, are involved in the mechanism responsible for producing lesions of sarcoid meningoencephalitis.

[An autopsy case of corticobasal degeneration without prominent cortical pathology--an imitator of progressive supranuclear palsy]

We describe an autopsy case of parkinsonism with bradykinesia, muscle rigidity, and dementia as major symptoms. The patient had developed bradykinesia at the age of 62, and then muscle rigidity, a parkinsonian posture, bradylalia, and dementia gradually appeared. Neurological examination revealed rigidity in the neck and limbs, with motion and speech being generally slow. He lacked involuntary movements including alien hand, tremor, chorea, and dystonia. Vertical gaze palsy, both upward and downward was noted, but other cranial nerves were intact. He was diagnosed as suffering from PSP clinically based on vertical gaze palsy, bradykinesia, instability on standing and gait, and dementia. Levodopa was only transiently effective. Within three years he became bed-ridden and in a state of akinetic mutism. At age 65 he died from pneumonia. Neuropathology revealed severe neuronal degeneration and gliosis in the substantia nigra. Because atrophy of the tegmentum of brainstem, dentate nuclei, inferior olivary nuclei was very mild and Alzheimer neurofibrillary tangles in the brainstem were relatively few, PSP was ruled out. Cortical neuronal degeneration was not apparent, but in the deep layer of cingulate gyrus, frontal lobe, and insula, there were several ballooned neurons. Gallyas-Braak silver staining showed no tuft-shaped astrocytes, specific for PSP, but it disclosed astrocytic plaques in the basal ganglia and the cerebral cortex. At present, astrocytic plaques are recognized as a hallmark of corticobasal degeneration (CBD), along with ballooned neurons in the cerebral cortex. The present case thus illustrates that CBD has a wide spectrum and may include cases in which degeneration of cerebral cortex is very mild.

Neuronal distribution and subcellular localization of HCNP-like immunoreactivity in rat small intestine

A novel peptide, hippocampal cholinergic neurostimulating peptide (HCNP), originally purified from young rat hippocampus, affects the development of specific cholinergic neurons of the central nervous system in vitro. In this study, HCNP-like-immunoreactive nerve processes and nerve cell bodies were identified by electron microscopic immunocytochemistry in the rat small intestine. Labeled nerve processes were numerous in the circular muscle layer and around the submucosal blood vessels. In the submucosal and myenteric plexuses, some HCNP-like-immunopositive nerve cell bodies and nerve fibers were present. The reaction product was deposited on the membranes of various subcellular organelles, including the rough endoplasmic reticulum, Golgi saccules, ovoid electron-lucent synaptic vesicles in axon terminals associated with submucosal and myenteric plexuses, and the outer membranes of a few mitochondria. The synaptic vesicles of HCNP-like positive terminals were 60-85 nm in diameter. The present data provide immunocytochemical evidence that HCNP-like-positive nerve cell bodies and nerve fibers are present in the submucosal and myenteric plexuses of the rat small intestine. An immunohistochemical light microscopic study using mirror-image sections revealed that in both the submucosal and myenteric ganglia, almost all choline acetyltransferase (ChAT)-immunoreactive neurons were also immunoreactive for HCNP. These observations suggest (i) that HCNP proper and/or HCNP precursor protein is a membrane-associated protein with a widespread subcellular distribution, (ii) that HCNP precursor protein may be biosynthesized within neurons localized in the rat enteric nervous system, and (iii) that HCNP proper and/or HCNP precursor protein are probably stored in axon terminals.

Hippocampal cholinergic neurostimulating peptides (HCNP)

Neuronal development and differentiation require a variety of cell interactions. Diffusible molecules from target neurons play an important part in mediating such interactions. Our early studies used explant culture technique to examine the factors that enhance the differentiation of septo-hippocampal cholinergic neurons, and they revealed that several components resident in the hippocampus are involved in the differentiation of presynaptic cholinergic neurons in the medial septal nucleus. One of these components, originally purified from young rat hippocampus, is a novel undecapeptide (hippocampal cholinergic neurostimulating peptide; HCNP); this enhances the production of ChAT, but not of AchE. Later experiments revealed that: (1) a specific receptor appears to mediate this effect; (2) NGF and HCNP act cooperatively to regulate cholinergic phenotype development in the medial septal nucleus in culture; and (3) these two molecules differ both in their mechanism of release from the hippocampus and their mechanism of action on cholinergic neurons. The amino acid sequence deduced from base sequence analysis of cloned HCNP-precursor protein cDNA shows that HCNP is located at the N-terminal domain of its precursor protein. The 21 kDa HCNP precursor protein shows homology with other proteins, and it functions not only as an HCNP precursor, but also as a binding protein for ATP, opioids and phosphatidylethanolamine. The distribution and localization of HCNP-related components and the expression of their mRNAs support the notion that the precursor protein is multifunctional. In keeping with its multiple functions, the multiple enhancers and promoters found in the genomic DNA for HCNP precursor protein may be involved in the regulation of its gene in a variety of cells and at different stages of development. Furthermore, several lines of evidence obtained from studies of humans and animal models suggest that certain types of memory and learning disorders are associated with abnormal accumulation and expression of HCNP analogue peptide and/or its precursor protein mRNA in the hippocampus.

Increased expression of hippocampal cholinergic neurostimulating peptide-related components and their messenger RNAs in the hippocampus of aged senescence-accelerated mice

Hippocampal cholinergic neurostimulating peptide stimulates cholinergic phenotype development by inducing choline acetyltransferase in the rat medial septal nucleus in vitro. Adult senescence-accelerated-prone mice/8, a substrain of the senescence-accelerated-prone mouse, show a remarkable age-accelerated deterioration in learning and memory. We cloned mouse hippocampal cholinergic neurostimulating peptide precursor protein complementary DNA. The deduced amino acid sequence showed that the neurostimulating peptide itself is the same as that found in the rat. In situ hybridization revealed that the highest expression of the precursor protein messenger RNA was in hippocampal pyramidal neurons. Compared with a strain of senescence-accelerated-resistant mouse (control mouse), adult senescence-accelerated-prone mice/8 showed increased expression of both the precursor messenger RNA and the neurostimulating peptide-related immunodeposits in the hippocampal CA1 field. The deposits were intensely and diffusely precipitated in neuropils throughout the strata oriens and radiatum in senescence-accelerated-prone mice/8, but not in control mice. The neurostimulating peptide content in the hippocampus was higher in senescence-accelerated-prone mice/8 than in control mice, while its precursor protein itself was not different between the two strains. Furthermore, our previous and present data show that the medial septal and hippocampal choline acetyltransferase activity was significantly lower in senescence-accelerated-prone mice/8 than in control mice. The data suggest that, in hippocampal neurons in adult senescence-accelerated-prone mice/8, the production of hippocampal cholinergic neurostimulating peptide precursor protein in neuronal somata, which is associated with an increased expression of its messenger RNA in the CA1 field, occurs as a consequence of low activity in their presynaptic cholinergic neurons. This is followed by accelerated processing to generate bioactive peptide and transport to its functional fields. However, certain mechanisms reduce the release of the peptide and lead to its accumulation in the neuropil. These disturbances of the septohippocampal cholinergic system might be the biochemical mechanism underlying the characteristic deterioration of senescence-accelerated-prone mice/8.