Neuropeptides in neurological disease

Brain and CSF somatostatin concentrations in patients with psychiatric or neurological illness. An overview

Somatostatin was originally isolated as a 14-amino-acid peptide from the ovine hypothalamus. The peptide has a widespread regional distribution within the central and peripheral nervous systems, as well as in peripheral organs. Preservation of the chemical structure over a wide range of vertebral species indicates important functional roles of the peptide. Recent results about the role of somatostatin and related peptides in different psychiatric (depression, schizophrenia, Alzheimer's disease) and neurological (Huntington's disease, multiple sclerosis, Parkinson's disease) diseases, and the effects on the hypothalamic-pituitary-adrenal axis are summarized. Also, the influence of some psychotropic drugs (halo-peridol, carbamazepine) on somatostatin levels in cerebrospinal fluid is discussed.

Met5-enkephalin-Arg6-Gly7-Leu8 immunoreactivity in rat and human cerebrospinal fluid: influence of neuroleptic drugs and electroconvulsive shock

Met5-Enkephalin-Arg6-Gly7-Leu8 immunoreactivity was quantitated in both rat and human cerebrospinal fluid (CSF) by radioimmunoassay with a carboxy-terminal directed antiserum. The immunoreactivity in CSF was chromatographically characterized in both species and was found to consist almost exclusively of high molecular weight forms. In human CSF there was approximately 300 fmol/ml and in the rat 1,500 fmol/ml of immunoreactivity. The possibility of a rostro-caudal gradient was examined in the human by analyzing the first and the twenty-fifth ml of CSF drawn during a lumbar puncture: none was found. The immunoreactivity was fairly stable; no loss of immunoreactivity was observed after 24 h of incubation of rat CSF at 37 degrees C. Electroconvulsive shock (ECS) produced a significant elevation in CSF content but only after a course of chronic administration; a single acute ECS produced no increase. Human subjects with schizophrenia who were being treated with antipsychotic drugs had elevated levels of immunoreactivity in comparison to non-mediated patients and normals. The high levels of this immunoreactivity in CSF, its stability and the evidence that the content can change with physiological and pharmacological manipulation indicate that Met5-Enkephalin-Arg6-Gly7-Leu8 immunoreactivity can serve as a new and useful CSF marker for investigating the CNS enkephalin system in neurological or psychiatric disorders.

Regional localization of the mRNA coding for the neuropeptide cholecystokinin in the rat brain studied by in situ hybridization

The regional localization of mRNA coding for the neuropeptide cholecystokinin (CCK) has been studied in the rat brain by in situ hybridization using a 32P-labelled synthetic 32 mer oligonucleotide. Autoradiograms were quantified using computer-assisted microdensitometry. High levels of hybridization were observed in the neocortex, claustrum, endopiriform nucleus, cingular cortex, amygdala, olfactory bulb, hippocampus, ventral tegmental area, geniculate nucleus, several thalamic nuclei and substantia nigra compacta. Very weak signal was detected in the striatum, the cerebellum and the brainstem. The topographic distribution of CCK neurons observed overlaps in part with that previously described by immunohistochemical techniques. However, some discrepancies were also found, particularly in the thalamus. These results show that in situ hybridization with oligonucleotide probes together with a semiquantitative method described can be used to map the expression of the CCK mRNA in rat brain sections as well as its modification after pharmacological or physiological manipulations.

Experimental approaches to age-related cognitive impairments

Rats exhibit morphological, biochemical, and metabolic changes in their brains, as well as cognitive deficits, with aging. Aged rats were found to be significantly impaired compared to young rats in a water maze task and test of motor coordination, and show reduced locomotor activity and exploration. Although aged rats did exhibit deficits as a group, not all aged rats were impaired. Additionally, the subgroup that was impaired on one task was not necessarily the subgroup that was impaired on another task. The cholinergic projection neurons in the basal forebrain region were significantly atrophied in the aged rodent. The degree of atrophy was highly correlated with the cognitive impairment exhibited on the Morris water maze task. Swollen choline acetyltransferase (ChAT)-positive "plaque-like" structures were observed in the neocortex of the aged but not the young rats. Declines in cholinergic activity in the brain has also been observed during aging. Biochemical measurements of ChAT in the basal forebrain region of aged rats revealed small but consistent decreases in ChAT activity compared to young rats. General metabolic activity, measured by the 2-deoxyglucose method, was also decreased in the hippocampal CA1 and CA3 fields, the dentate gyrus, the medial septal-diagonal band area, and the prefrontal cortex of aged rats. There was a significant correlation between the decrease in glucose utilization and deficits on the Morris water maze. Most aged rats exhibit pathological EEG patterns as reflected by frequent long-duration high voltage neocortical spindles (HVS) during immobility. Bilateral lesions of the nucleus basalis and scopolamine treatment increased the incidence of HVS, thereby mimicking changes in the aged brain. We attempted to ameliorate the cognitive deficits observed in subgroups or impaired rats by either: (1) implanting fetal cells of basal forebrain origin into the hippocampus, or (2) infusing nerve growth factor (NGF) chronically into the lateral ventricle. The grafts appeared to facilitate an improvement in the ability of the impaired aged rats to perform in the Morris water maze. This improved performance was reversed by injections of atropine at doses that did not affect the behavior of young animals that performed well in the same task. These results suggest that enhancement of the cholinergic system could have an effect on the performance of the impaired aged animals. The study of the effects of infusions of NGF clearly demonstrate that the ability of impaired aged rats to remember what they had previously learned was increased after NGF treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Somatostatin and neuropeptide Y concentrations in pathologically graded cases of Huntington's disease

Somatostatin and neuropeptide Y concentrations have previously been reported to be increased in the basal ganglia in Huntington's disease (HD). In the present study we have extended these findings by examining both somatostatin-like immunoreactivity (SLI) and neuropeptide Y-like immunoreactivity (NPYLI) in cases of HD, which were graded according to the severity of pathological degeneration in the striatum. In addition, we surveyed a large number of subcortical nuclei and cortical regions for alterations. Both SLI and NPYLI were significantly increased about threefold in the caudate, putamen, and the nucleus accumbens. Increases in mild and severe grades were similar, which is consistent with a relative but not absolute sparing of striatal aspiny neurons in which somatostatin and neuropeptide Y are colocalized. Significant increases of NPYLI were also found in the external pallidum, subthalamic nucleus, substantia nigra compacta, claustrum, anterior and dorsomedial thalamus, bed nucleus of the stria terminalis, and locus ceruleus. SLI was significantly increased in the external pallidum, red nucleus, and locus ceruleus. Measurements of both neuropeptides were made in 24 regions of the cerebral cortex. Significant increases in both NPYLI and SLI were found in the frontal cortex (Brodmann areas 6, 8, 9, 10, 11, and 45) and temporal cortex (Brodmann area 21), whereas NPYLI was also increased in Brodmann areas 12, 20-22, 25, and 42. Alterations in the cerebral cortex were as pronounced in cases with mild striatal pathological changes as in those with severe striatal pathological changes. These alterations may occur early in HD and could reflect a selective sparing of somatostatin-neuropeptide Y cortical neurons combined with cortical atrophy.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of basal forebrain in the primary cholinergic vasodilation in rat neocortex produced by systemic administration of cismethrin

The pyrethroid insecticide cismethrin (9 mumol/kg) causes a large blood flow increase in cerebral cortex, without a parallel increase in metabolism. A unilateral lesion of the basal forebrain attenuated the blood flow increase in the cortex ipsilateral to the lesion but augmented that in the contralateral cortex. Cortical choline acetyltransferase was similarly affected. Atropine sulphate substantially reduced the flow increase and was additive to the lesion effects. Systemic cismethrin is thus capable of activating a cholinergic vasodilation in the cortex and, in the parietal cortex at least, a substantial proportion of the flow increase is mediated by extrinsic projections from the basal forebrain.

Spinal subarachnoid injection of somatostatin causes neurological deficits and neuronal injury in rats

The tetradecapeptide somatostatin produced dose-related neurological deficits following subarachnoid injection in the lumbar spinal cords of rats. Lower pharmacological doses (1.6 and 3.1 nmol, i.t.) of somatostatin caused only transient deficits, while higher doses (6.2-25 nmol, i.t.) caused persistent deficits characterized by motor and sensory impairments in hindlimbs and tail, hindlimb edema, priapism, bladder atony with infarction, and urinary incontinence. Pretreatment with 0.3 nmol of the somatostatin receptor antagonist cyclo[7-aminoheptanoyl-Phe-D-Trp-Lys-Thr(Bzl)] blocked the hindlimb paralytic effects of 3.1 and 6.2 nmol of somatostatin, and significantly improved neurological recovery injection of 12.5 nmol of somatostatin. Higher doses of the antagonist produced hindlimb paralysis by itself. Neuroanatomical evaluations revealed extensive cell loss and necrosis in the lumbosacral spinal cords of rats paralyzed by 25 nmol of somatostatin. Collectively, these results suggest that through interactions with a receptor, somatostatin destroys neurons involved in diverse spinal cord functions.

Dopaminergic system and monoamine oxidase-B activity in Alzheimer's disease

The possible involvement of dopaminergic neurons in dementia of Alzheimer type (AD/SDAT) was studied in autopsied brains from 20 patients with AD/SDAT. Dopamine (DA) concentrations were decreased significantly in the temporal cortex, hippocampal cortex and hippocampus in AD/SDAT patients. Levels of homovanillic acid (HVA) were not altered compared to controls. The HVA/DA ratio was significantly higher in the hippocampus of AD/SDAT patients, suggesting overactivity of the remaining DA neurons. Histological findings of substantia nigra suggesting coexistent pathology of Parkinson's disease (PD) found in 25% of cases were associated with lowered levels of DA in striatum and with reduced HVA in CSF. The activity of monoamine oxidase-B was significantly increased in the cortical areas and in the hippocampus, obviously reflecting the underlying cell loss and substantial gliosis in these areas of the brain. In general, DA neurons seemed to be only mildly involved in AD/SDAT. Coexistent PD pathology can explain the loss of DA in the striatum and the presence of clinical PD symptoms in some patients with AD/SDAT. Otherwise the clinical relevance of these dopaminergic alterations is unclear.

Alz-50 antibody recognizes Alzheimer-related neuronal changes

Alz-50 is a monoclonal antibody directed against an antigen present in Alzheimer's disease. Unlike conventional pathological stains that reveal only neurons with neurofibrillary tangles (NFTs), Alz-50 recognizes neurons that contain NFTs and additional neurons that do not. Our investigation of the topographical distribution of both NFT-containing and non-NFT-containing neurons recognized by Alz-50 reveals that they are both found primarily in certain cytoarchitectural areas and lamina that have been established as consistent sites for NFT pathology. Some of the neurons recognized by Alz-50 appear histopathologically normal. We suggest that Alz-50 recognizes an antigen in neurons that both precedes and accompanies NFT formation. Thus, it may mark a point early in cellular pathology before irreversible cytoskeletal and degenerative changes occur.

Stimulation of lipolytic enzymes in Alzheimer's disease

The activities of monoacylglycerol and diacylglycerol lipases were 6 to 8 times higher in plasma membrane and synaptosomal plasma membrane fractions of nucleus basalis from patients with Alzheimer's disease than in those membranes from normal human brains. Membranes from the hippocampus region of Alzheimer-affected brains also showed consistently higher activities of monoacylglycerol and diacylglycerol lipases than those from control brains. These results indicate a stimulation of lipolytic enzymes in nucleus basalis and hippocampus regions in patients with Alzheimer's disease.

A detailed examination of substance P in pathologically graded cases of Huntington's disease

Substance P concentrations have been found to be reduced in the basal ganglia in Huntington's disease (HD). In order to further examine this finding in the present study we measured substance P-like immunoreactivity (SPLI) in cases of HD which had been graded as to the severity of pathological changes in the striatum. Marked significant reductions of SPLI were found in all striatal nuclei which were significantly correlated with the percentage of neuronal loss in the varying pathologic grades. Similar changes were found in the projection sites of striatal substance P neurons, the globus pallidus interna and the substantia nigra. These changes are consistent with a loss of striatal substance P containing projection neurons in HD. Significant reductions in SPLI were also found in the external pallidum, bed nucleus of the stria terminalis and the subthalamic nucleus. Small significant increases in SPLI (20-30%) were found in 3 frontal cortical regions (Brodmann areas 6, 8 and 9). The finding of neurochemical changes in the subthalamic nucleus is of particular interest since lesions in this nucleus are known to result in chorea and therefore might contribute to the chorea which is a cardinal symptom of HD.

The coexistence and differentiation of late onset Huntington's disease and Alzheimer's disease. A case report and review of the literature

The case report presented is clinically compatible with late onset HD. The diagnosis was initially obscured by a lack of family history due to the early death of both parents and siblings. The presence of symptoms at the age of 59 in one offspring is consistent with the intrafamilial transmission of late onset HD disease. The early neuropsychometric data were consistent with the cognitive changes of HD, particularly with the loss of higher cognitive functions, memory and the relative decline in the performance IQ with the preservation of language skills. The psychiatric symptoms of emotional lability and apathy were also congruent with the diagnosis of HD. The atypical features of this patient's course, including progressively severe dementia, seizures and rigidity, may have provided clinical clues to the coexistence of both AD and HD. The absence of caudate atrophy on serial CT scans in this patient, although inconsistent with the gross findings reported on postmortem exam, perhaps could be explained by the 3 1/2-year interval between the last CT scan and death. Further, it has been noted previously that pathological changes tend to lag behind the clinical manifestations of the disease. The pathologic findings on autopsy were confirmatory for the presence of both AD and HD in this patient. Genetic counseling for this family is now most appropriate.

Peptide radioimmunoassays: a BASIC program for data reduction

A BASIC computer program is listed and described which may be used for calculating large amounts of data generated by radioimmunoassays. The user is given the opportunity to construct standard curves and to calculate mass quantities from raw counts or to incorporate previously determined protein values with mass quantities for final data expression. Calculated data may be viewed onscreen or obtained as printed copy.

Neuropathology of Rett syndrome

Rett syndrome is an increasingly recognized progressive disorder in females, commencing in infancy and characterized by autistic behavior, gait ataxia, stereotyped movements, seizures and generalized growth and mental retardation, possibly associated with disorders of central biogenic amine synthesis. The gene locus and pathogenesis of Rett syndrome are unknown. Autopsy studies in nine girls dying between 4 and 17 years, and sural nerve and muscle biopsies from two girls aged 3 and 17 years showed: (1) diffuse cortical atrophy/micrencephaly, with a decrease in brain weight by 12% to 34% of age-matched controls, apparently related to the duration of the disorder; (2) mild diffuse cortical atrophy with increased amounts of neuronal lipofuscin and occasional mild gliosis, but without signs of a storage disorder; (3) underpigmentation of the zona compacta nigrae, which showed fewer well-pigmented neurons for age and fewer melanin granules per neuron, while total numbers of nigral neurons and the substructure of neuromelanin were normal for age. No pathological changes were seen in other transmitter-specific brain stem nuclei; (4) immunoreactivity for tyrosine hydroxylase was slightly reduced in nigral and hypothalamic neurons, and the pituitary gland showed decreased immunoreaction for prolactin and growth hormone; (5) ultrastructurally, in frontal cortex and caudate nucleus, isolated abnormal neurites and reactive or degenerative axonal swellings were seen; the latter are possibly related to the nigral changes, suggesting some dysfunction of the dopaminergic nigrostriatal system, which is supported by neurochemical data; (6) preliminary biochemical studies revealed increased beta-endorphines in thalamus and cerebellum; (7) peripheral nerves demonstrated increase in small fibers without demyelination and increased numbers of neurofilaments in axons, suggesting distal axonopathy, while skeletal muscle showed alterations in the sarcoplasmic reticulum with circular profiles in the Z-filaments. These nonspecific changes may be interpreted as early signs of denervation. The variety of lesions in the central, neuroendocrine and peripheral neuromuscular systems in Rett syndrome are discussed with regard to their clinical and biochemical significance.

Neuron numbers and dendritic extent in normal aging and Alzheimer's disease

Factors which limit the interpretation of studies of aging brain include: secular trends, species and strain differences, effects of tissue processing, and bias which may be introduced at many levels of an experimental design. With these limitations considered, evidence is reviewed regarding neuron numbers and dendritic extent in normally aging rodent, monkey and human brain and in Alzheimer's disease. It is concluded that neuron loss and change in dendritic extent in normal aging are regionally specific, and that corresponding brain regions do not always change in similar ways in rodents and primates. It is suggested that such differences may, in part, be due to inconsistent definitions of 'aged' among species. In Alzheimer's disease there is excess neuron loss and dendritic regression in some, but not all, brain regions. Measures of the morphological substrates of brain function show appreciable overlap between AD and control groups. It is hypothesized that the static, post-mortem status of brain morphology may not adequately reflect the functional capabilities of the dynamic morphology of the living brain.

Decreased muscarinic receptor binding in cerebral cortex and hippocampus in Alzheimer's disease

Muscarinic (cholinergic) receptor binding sites (MRB) were studied by determining the 3H-QNB binding in four cortical areas and hippocampus of 20 histologically confirmed Alzheimer patients and comparing these with corresponding controls. Alzheimer patients dying at younger age (less than or equal to 80) with profound decrease in choline-acetyltransferase activity (by 61-85%) and without any, possibly MRB modifying, drug treatment showed 30% decrease in MRB in the frontal cortex (p less than 0.05), 28% in the temporal cortex (p less than 0.05) and 37% in the hippocampus (p less than 0.01). These findings further suggest that muscarinic receptors are affected in Alzheimer's disease, at least in advanced state of the disease.