Reduced cholecystokinin-like and somatostatin-like immunoreactivity in limbic lobe is associated with negative symptoms in schizophrenia

Cholecystokinin-Mediated Neuromodulation of Anxiety and Schizophrenia: A "Dimmer-Switch" Hypothesis

Cholecystokinin (CCK), the most abundant brain neuropeptide, is involved in relevant behavioral functions like memory, cognition, and reward through its interactions with the opioid and dopaminergic systems in the limbic system. CCK excites neurons by binding two receptors, CCK1 and CCK2, expressed at low and high levels in the brain, respectively. Historically, CCK2 receptors have been related to the induction of panic attacks in humans. Disturbances in brain CCK expression also underlie the physiopathology of schizophrenia, which is attributed to the modulation by CCK1 receptors of the dopamine flux in the basal striatum. Despite this evidence, neither CCK2 receptor antagonists ameliorate human anxiety nor CCK agonists have consistently shown neuroleptic effects in clinical trials. A neglected aspect of the function of brain CCK is its neuromodulatory role in mental disorders. Interestingly, CCK is expressed in pivotal inhibitory interneurons that sculpt cortical dynamics and the flux of nerve impulses across corticolimbic areas and the excitatory projections to mesolimbic pathways. At the basal striatum, CCK modulates the excitability of glutamate, the release of inhibitory GABA, and the discharge of dopamine. Here we focus on how CCK may reduce rather than trigger anxiety by regulating its cognitive component. Adequate levels of CCK release in the basal striatum may control the interplay between cognition and reward circuitry, which is critical in schizophrenia. Hence, it is proposed that disturbances in the excitatory/ inhibitory interplay modulated by CCK may contribute to the imbalanced interaction between corticolimbic and mesolimbic neural activity found in anxiety and schizophrenia.

The potential role of cholecystokinin in schizophrenia: review and update

The role of the neuropeptide cholecystokinin in schizophrenia has been widely explored because of its modulating action on midbrain dopamine neurons. The recent discovery of more specific receptor subtype cholecystokinin antagonists should be considered as potential treatment for schizophrenia with fewer side effects. This paper reviews cholecystokinin/dopamine interactions in animal and human studies. Clinical trials with cholecystokinin agonists and antagonists in schizophrenia are updated.

The past and future of novel, non-dopamine-2 receptor therapeutics for schizophrenia: A critical and comprehensive review

Since the discovery of chlorpromazine in the 1950's, antipsychotic drugs have been the cornerstone of treatment of schizophrenia, and all attenuate dopamine transmission at the dopamine-2 receptor. Drug development for schizophrenia since that time has led to improvements in side effects and tolerability, and limited improvements in efficacy, with the exception of clozapine. However, the reasons for clozapine's greater efficacy remain unclear, despite the great efforts and resources invested therewith. We performed a comprehensive review of the literature to determine the fate of previously tested, non-dopamine-2 receptor experimental treatments. Overall we included 250 studies in the review from the period 1970 to 2017 including treatments with glutamatergic, serotonergic, cholinergic, neuropeptidergic, hormone-based, dopaminergic, metabolic, vitamin/naturopathic, histaminergic, infection/inflammation-based, and miscellaneous mechanisms. Despite there being several promising targets, such as allosteric modulation of the NMDA and α7 nicotinic receptors, we cannot confidently state that any of the mechanistically novel experimental treatments covered in this review are definitely effective for the treatment of schizophrenia and ready for clinical use. We discuss potential reasons for the relative lack of progress in developing non-dopamine-2 receptor treatments for schizophrenia and provide recommendations for future efforts pursuing novel drug development for schizophrenia.

Identifying a system of predominant negative symptoms: Network analysis of three randomized clinical trials

BACKGROUND

Reasons for the recent mixed success of research into negative symptoms may be informed by conceptualizing negative symptoms as a system that is identifiable from network analysis. We aimed to identify: (I) negative symptom systems; (I) central negative symptoms within each system; and (III) differences between the systems, based on network analysis of negative symptoms for baseline, endpoint and change.

METHODS

Patients with chronic schizophrenia and predominant negative symptoms participated in three clinical trials that compared placebo and amisulpride to 60days (n=487). Networks analyses were computed from the Scale for the Assessment of Negative Symptoms (SANS) scores for baseline and endpoint for severity, and estimated change based on mixed models. Central symptoms to each network were identified. The networks were contrasted for connectivity with permutation tests.

RESULTS

Network analysis showed that the baseline and endpoint symptom severity systems formed symptom groups of Affect, Poor responsiveness, Lack of interest, and Apathy-inattentiveness. The baseline and endpoint networks did not significantly differ in terms of connectivity, but both significantly (P<0.05) differed to the change network. In the change network the apathy-inattentiveness symptom group split into three other groups. The most central symptoms were Decreased Spontaneous Movements at baseline and endpoint, and Poverty of Speech for estimated change.

CONCLUSIONS

Results provide preliminary evidence for: (I) a replicable negative symptom severity system; and (II) symptoms with high centrality (e.g., Decreased Spontaneous Movement), that may be future treatment targets following replication to ensure the curent results generalize to other samples.

Behavioral and cortical EEG evaluations confirm the roles of both CCKA and CCKB receptors in mouse CCK-induced anxiety

This study investigated the roles of cholecystokinin (CCK)(A) and CCK(B) receptors on CCK-4-induced anxiety-like behaviors in mice through behavioral and neural evaluations. Anxiety-like behaviors in mice were induced by an intracerebroventricular (i.c.v.) administration of CCK-4, which can bind to both CCK(A) and CCK(B) receptors. The effects of CCK(A) and CCK(B) receptor antagonists (devazepide and CI-988, respectively) were examined using mouse anxiety tests (elevated-plus maze and light-dark box) and also by examining neuronal activities through EEG monitoring and c-Fos immunohistochemistry in the cortex and amygdala. CCK-4 (3 μg/kg of body weight i.c.v.) significantly induced mouse anxiety-like behaviors in the anxiety tests and also affected their EEG patterns with respect to pre-drug tracing, resulting in increase in spectral power in relative power distribution in the delta and theta bands (0.5-5 Hz frequency bands) and also in increase in c-Fos immunopositive neuron counts. These CCK-4 effects were completely suppressed by 1.0mg/kg CCK(B) receptor antagonist, CI-988, while the same amount of CCK(A) receptor antagonist, devazepide was partly able to suppress the same effects. These findings indicated that not only CCK(B) receptors but also CCK(A) receptors in the brain play important roles in regulating anxiety-like behaviors in mice. The present study also proposed a possibility that cortical EEG is useful for assessing anxiety.

Somatostatinergic systems: an update on brain functions in normal and pathological aging

Somatostatin is highly expressed in mammalian brain and is involved in many brain functions such as motor activity, sleep, sensory, and cognitive processes. Five somatostatin receptors have been described: sst(1), sst(2) (A and B), sst(3), sst(4), and sst(5), all belonging to the G-protein-coupled receptor family. During the recent years, numerous studies contributed to clarify the role of somatostatin systems, especially long-range somatostatinergic interneurons, in several functions they have been previously involved in. New advances have also been made on the alterations of somatostatinergic systems in several brain diseases and on the potential therapeutic target they represent in these pathologies.

Cholecystokinin: a multi-functional molecular switch of neuronal circuits

Cholecystokinin (CCK), a peptide originally discovered in the gastrointestinal tract, is one of the most abundant and widely distributed neuropeptides in the brain. In spite of its abundance, recent data indicate that CCK modulates intrinsic neuronal excitability and synaptic transmission in a surprisingly cell-type specific manner, acting as a key molecular switch to regulate the functional output of neuronal circuits. The central importance of CCK in neuronal networks is also reflected in its involvement in a variety of neuropsychiatric and neurological disorders including panic attacks and epilepsy.

Studies on the hippocampal formation: From basic development to clinical applications: Studies on schizophrenia

The hippocampal formation plays a critical role in cognitive function. The developmental events that shape the hippocampal formation are continuing to be elucidated and their implications for brain function are emerging as well as applying those advances to interventions that have important possibilities for the treatment of brain dysfunction. The story told in this chapter is about the use of the in oculo transplant method to illuminate intrinsic and extrinsic features that underlie the development of the dentate gyrus and adjacent hippocampus and the role of one molecule in the hippocampus and schizophrenia. Schizophrenia, originally conceptualized as a dysfunction in dopaminergic neurotransmission, is now known to involve multiple neuronal systems. Dysfunction of hippocampal neurons is emerging as one of its signature pathological features. Basic insights into the development and function of hippocampal interneurons form the basis of a new treatment initiative for this illness. Evidence for the role of the alpha 7-nicotinic acetylcholine receptor in the development and function of these neurons in rodents has led to human trials of nicotinic agonists for cognitive dysfunction in schizophrenia and the possibility of improving hippocampal development in children at risk for schizophrenia by perinatal supplementation with choline, which can act as an alpha 7-nicotinic acetylcholine receptor agonist.

Association between CCK-AR gene and schizophrenia with auditory hallucinations

OBJECTIVE

Previous studies on a possible association between CCK-AR polymorphisms and schizophrenia have been controversial. The aim of the present study was to assess a potential association between schizophrenic patients with auditory hallucinations and polymorphisms of the CCK-AR gene.

METHODS

A set of single nucleotide polymorphisms mainly located in the regulatory region of the CCK-AR gene was analysed in a sample of 163 Diagnostic and statistical manual of mental disorders-IV-diagnosed schizophrenic patients and 162 healthy controls.

RESULTS

Significant differences in the genotype (P=0.011) and allele (P=0.0009) frequencies of the +121C/G SNP (located in the 5' regulatory region) were found between patients and controls. The excess of the C allele in the patient group remained significant after Bonferroni correction (P=0.03). However, functional in vitro assays, did not reveal significant differences on gene expression between +121G and +121C alleles of this SNP. Further investigations revealed two risk haplotypes: +121C/+978A/+984T (P=0.01) and +121C/+978T/+984C (P=0.0091) as well as a protective haplotype: +121G/+978T/+984T (P=0.0001).

CONCLUSION

Our data support a possible role of the CCK-AR gene in the vulnerability to schizophrenia in patients with auditory hallucinations, and suggest remarkable allele heterogeneity.

The anatomy of co-morbid neuropsychiatric disorders based on cortico-limbic synaptic interactions

Many brain disorders appear to involve dysfunctions of aminergic systems. Alterations in dopamine activity may underpin both schizophrenia and the establishment and maintenance of drug dependence while disruption of serotonergic signalling may be crucial in both depression and schizophrenia. The co-existence of nicotine and alcohol abuse with depression and schizophrenia is well-documented as is the particular vulnerability of adolescents. At the same time, a common group of brain structures is increasingly implicated in neuropathological studies. For example, depression may involve a lack of serotonin signalling, particularly in the prefrontal cortex, while in schizophrenia there is evidence for reduced dopamine signalling in the same brain region, co-existing with hyperactivity in the mesolimbic dopamine pathway. Increased dopamine release from the mesolimbic dopamine pathway is also a common factor of drugs of abuse. Furthermore, the control of motivational behaviour and dopamine release is apparently modified by hippocampal and amygdala activity, both brain regions showing pathological changes in schizophrenia and depression. Our work has focused on the intricate synaptic interactions of aminergic terminals and cortical and subcortical neurons in order to unravel the anatomical basis for these disorders and their treatments. We show convergence of dopamine and cortical inputs onto single neurons in the nucleus accumbens, and between different cortical inputs to individual neurons, providing a basis for the gating mechanisms attributed to these interactions. We have also examined local and extrinsic connections in the prefrontal cortex and the basis for regulation of both cortical neurons and midbrain dopamine neurons by serotonin from the raph é nucleus. Together with data concerning subcellular receptor distributions, this information provides a detailed synaptic framework for interpreting behavioural, pharmacological and physiological data and enhances our understanding of possible circuitry underlying comorbidity of disorders such as schizophrenia and depression with drug abuse, information invaluable in the introduction of enhanced therapies.

Involvement of neuropeptide systems in schizophrenia: human studies

Neuropeptides are heterogeneously distributed throughout the digestive, circulatory, and nervous systems and serve as neurotransmitters, neuromodulators, and hormones. Neuropeptides are phylogenetically conserved and have been demonstrated to regulate numerous behaviors. They have been hypothesized to be pathologically involved in several psychiatric disorders, including schizophrenia. On the basis of preclinical data, numerous studies have sought to examine the role of neuropeptide systems in schizophrenia. This chapter reviews the clinical data, linking alterations in neuropeptide systems to the etiology, pathophysiology, and treatment of schizophrenia. Data for the following neuropeptide systems are included: arginine-vasopressin, cholecystokinin (CCK), corticotropin-releasing factor (CRF), interleukins, neuregulin 1 (NRG1), neurotensin (NT), neuropeptide Y (NPY), opioids, secretin, somatostatin, tachykinins, thyrotropin-releasing hormone (TRH), and vasoactive intestinal peptide (VIP). Data from cerebrospinal fluid (CSF), postmortem and genetic studies, as well as clinical trials are described. Despite the inherent difficulties associated with human studies (including small sample size, variable duration of illness, medication status, the presence of comorbid psychiatric disorders, and diagnostic heterogeneity), several findings are noteworthy. Postmortem studies support disease-related alterations in several neuropeptide systems in the frontal and temporal cortices. The strongest genetic evidence supporting a role for neuropeptides in schizophrenia are those studies linking polymorphisms in NRG1 and the CCKA receptor with schizophrenia. Finally, the only compounds that act directly on neuropeptide systems that have demonstrated therapeutic efficacy in schizophrenia are neurokinin receptor antagonists. Clearly, additional investigation into the role of neuropeptide systems in the etiology, pathophysiology, and treatment of schizophrenia is warranted.

Clozapine but not haloperidol suppresses the changes in the levels of neuropeptides in MK-801-treated rat brain regions

Noncompetitive NMDA receptor antagonist (+)MK-801 is known to induce neurotoxicity and schizophrenia-like symptomatology where atypical neuroleptic clozapine is effective in contrast to typical neuroleptic, haloperidol. Although neuropeptides are implicated in memory and cognition, their roles in schizophrenia are not well understood. In the present study, we therefore examined the possible roles of neuropeptides, cholecystokinin (CCK) and somatostatin (SS) in the posterior cingulate/retrosplenial cortices (PC/RSC), frontal cortex, and hippocampus of a MK-801-induced schizophrenia-like model rat brain. This study further investigated the pretreated effect of atypical versus typical neuroleptics on the peptidergic system. SS mRNA and peptide levels significantly decreased in the PC/RSC and hippocampus but not in the frontal cortex 3 days after 0.5 mg/kg MK-801 treatment whereas CCK mRNA and peptide levels significantly decreased in all of the brain regions examined. Pretreatment with clozapine but not haloperidol completely recovered the changes in both mRNA and peptide levels of SS and CCK in those brain regions. These data suggest that peptidergic system in the brain presumably plays an important role in the control of negative schizophrenia.

Overlapping regional distribution of CCK and TPPII mRNAs in Cynomolgus monkey brain and correlated levels in human cerebral cortex (BA 10)

Tripeptidyl peptidase II (TPPII) is a high molecular weight exopeptidase important in inactivating extracellular cholecystokinin (CCK). Our aims were to study the anatomical localization of TPPII and CCK mRNA in the Cynomolgus monkey brain as a basis for a possible functional anatomical connection between enzyme (TPPII) and substrate (CCK) and examine if indications of changes in substrate availability in the human brain might be reflected in changes of levels of TPPII mRNA.

METHODS

mRNA in situ hybridization on postmortem brain from patients having had a schizophrenia diagnosis as compared to controls and on monkey and rat brain slices.

RESULTS

overlapping distribution patterns of mRNAs for TPPII and CCK in rat and monkey. High amounts of TPPII mRNA are seen in the neocortex, especially in the frontal region and the hippocampus. TPPII mRNA is also present in the basal ganglia and cerebellum where CCK immunoreactivity and/or CCK B receptors have been found in earlier studies, suggesting presence of CCK-ergic afferents from other brain regions. Levels of mRNAs for CCK and TPPII show a positive correlation in postmortem human cerebral cortex Brodmann area (BA) 10. TPPII mRNA might be affected following schizophrenia.

DISCUSSION

overall TPPII and CCK mRNA show a similar distribution in rat and monkey brain, confirming and extending earlier studies in rodents. In addition, correlated levels of TPPII and CCK mRNA in human BA 10 corroborate a functional link between CCK and TPPII in the human brain.

Increased synthesis but decreased processing of neuronal proCCK in prohormone convertase 2 and 7B2 knockout animals

In addition to its role as a gut hormone, cholecystokinin (CCK) is a widespread and potent neurotransmitter. Its biosynthesis requires endoproteolytic cleavage of proCCK at several mono- and dibasic sites by subtilisin-like prohormone convertases (PCs). Of these, PC1 and PC2 are specific for neuroendocrine cells. We have now examined the role of PC2 and its binding protein, 7B2, in the neuronal processing of proCCK by measurement of precursor, processing-intermediates and bioactive end-products in brain extracts from PC2- and 7B2-null mice and from corresponding controls. PC2-null mice displayed a nine-fold increase of cerebral proCCK concentrations, and a two-fold increase in the concentrations of the processing-intermediate, glycine-extended CCK, whereas the concentrations of transmitter-active (i.e. alpha-amidated and O-sulfated) CCK peptides were reduced (61%). Chromatography showed that O-sulfated CCK-8 still is the predominant transmitter-active CCK in PC2-null brains, but that the fraction of intermediate-sized CCK-peptides (CCK-58, -33 and -22) was eight-fold increased. 7B2-null brains displayed a similar pattern but with less pronounced precursor accumulation. In contrast with the cerebral changes, PC2 deficiency was without effect on proCCK synthesis and processing in intestinal endocrine cells, whereas 7B2 deficiency halved the concentration of bioactive CCK in the intestine. The results show that PC2 plays a major neuron-specific role in the processing of proCCK.

Neuropeptides involved in the pathophysiology of schizophrenia and major depression

The present review summarizes the findings on the role of neuropeptides in the pathophysiology of schizophrenia and major depression. Several neuropeptides as vasopressin and endorphins in particular, beta-endorphin and gamma-type endorphins, cholecystokinin (CCK), neurotensin, somatostatin and Neuropeptide Y have been implicated in schizophrenia. During the last decade, however, few attempts to explore the significance of most of these and other neuropeptides in the pathophysiology of the disease or their therapeutic potential are found in the literature. An exception is neurotensin, which exerts neuroleptic-like effects in animal studies, while CSF, brain and blood studies are inconclusive. Things are different in major depression. Here much attention is paid to the endocrine abnormalities found in this disorder in particular the increased activity of the hypothalamic-pituitary-adrenal (HPA) axis. Neuropeptides as corticotropin-releasing hormone (CRH), vasopressin and corticosteroids are implicated in the symptomatology of this disorder. As a consequence much work is going on investigating the influence of CRH and corticosteroid antagonists or inhibitors of the synthesis of corticosteroids as potential therapeutic agents. This review emphasizes the role of vasopressin in the increased activity of the HPA axis in major depression and suggests exploration of the influence of the now available non-peptidergic vasopressin orally active V1 antagonists.

Possible association of a cholecystokinin promoter variant to schizophrenia

Several lines of research indicate a cholecystokinin (CCK) deficit in schizophrenia patients. A C to T substitution was found in the promoter region of the CCK gene. We investigated this promoter variant in patients with schizophrenia and geographically-matchedcontrols. The T allele was detected in 24% of the 85 schizophrenics and 16% of the 247 controls. No significant difference in the T allele frequency was found between patients and controls (chi(2) = 2.77, P > 0.1). The schizophrenia sample was analyzed further along the dimensions of positive and negative symptoms. The patients with prominent negative symptoms presented a statistically significant association to the T allele (chi(2) = 4.13, P < 0.04). However, the significance disappeared after the Bonferroni correction (P > 0.15). Since the case-control analysis may present incorrect ethnic match between cases and controls, we applied the family-based tests to verify the above findings. Both transmission disequilibrium test (TDT; chi(2) = 5.33, P < 0.025 in 12 trios) and haplotype relative risk (HRR; chi(2) = 3.844, P < 0.05 in 60 trios) indicated a significantly high transmission of T allele to schizophrenia offspring probands from their parents. While our family-based tests seem to support the CCK involvement in schizophrenia, no definite conclusion can be drawn based on such a small sample size. This preliminary finding is subjected to future investigations.

GABAergic neuronal subtypes in the human frontal cortex--development and deficits in schizophrenia

Recent studies have provided evidence for a deficit of GABA-containing interneurons in the frontal cortex in schizophrenia. That this deficit might be brought about during early foetal or neonatal life is a hypothesis consistent with the substantial indications for a neurodevelopmental aetiology of the disease. GABAergic neurons can be defined by the presence of one of three types of calcium binding proteins, which are thought to have neuroprotective properties. We have undertaken an investigation into the postnatal ontology of these neuronal subtypes and find that calretinin expression is relatively constant and present from before birth, calbindin expression is also present early but redistributes in the cortex over the first months of life, while parvalbumin-immunoreactivity is not observed until between 3 and 6 months of age. Investigation of frontal cortical tissue taken post mortem from a series of schizophrenic patients and matched control subjects revealed that parvalbumin-, but not calretinin-immunoreactive cells are significantly diminished in schizophrenia. These observations support the hypothesis that GABAergic deficits in schizophrenia may stem from toxic events occurring during cortical development which selectively target immature neurons before protection by parvalbumin is conferred.

The alpha7-nicotinic acetylcholine receptor and the pathology of hippocampal interneurons in schizophrenia

This paper is a review of a recent findings on the pathology of hippocampal interneurons in schizophrenia, with specific emphasis on a protein expressed by these cells, the alpha7-nicotinic acetylcholine receptor subunit. Convergent information indicates that interneurons in the hippocampus and other forebrain structures are decreased in number and function in subjects with schizophrenia. Among the neurochemical markers that are decreased in the hippocampus are synapsin I, cholecystokinin, somatostatin, glutamic acid decarboxylase, and nitric oxide synthase. GABA uptake sites and the GABA synthetic enzyme glutamic acid decarboxylase are also diminished. Included among these findings is decreased binding of alpha-bungarotoxin, which binds to low-affinity nicotinic acetylcholine receptors, such as the alpha7-nicotinic receptor. Co-labeling experiments in rodents indicate that these markers are expressed on overlapping populations of hippocampal interneurons. Thus, the finding of decreased neurochemical function of hippocampal interneurons is a widely replicated finding, with different groups reporting markedly similar findings using independent post mortem samples and different neurochemical strategies. Decreased alpha-bungarotoxin binding or decreased alpha7-nicotinic receptor immunoreactivity has also been found in the frontal cortex and in the nucleus reticularis thalami of schizophrenic subjects. The alpha7-nicotinic receptor subunit gene on chromosome 15q14 is a site of heritability for schizophrenia and bipolar affective disorder, and in, particular, for a deficit in inhibitory neuronal function associated with these illnesses. Thus, the post mortem data are further supported by psychophysiologic and genetic investigations that indicate a deficit in inhibitory interneuronal function, involving the alpha7-nicotinic receptor. The alpha7-receptor is a ligand-gated ion channel that admits calcium ions into cells, and it has been proposed to have various developmental roles. Its malfunction may be part of the developmental pathogenesis of schizophrenia.

Cytokine and growth factor involvement in schizophrenia--support for the developmental model

Medical treatment with various cytokines can provoke psychiatric symptoms. Conversely, psychiatric patients can display abnormalities in cytokine and neurotrophic factor expression. Such observations have pointed to the potential contribution of cytokines and growth factors to schizophrenic pathology and/or etiology. The cellular targets of the relevant factors and the nature of their actions remain to be explored in mental illness, however. Recent physiological studies demonstrate that cytokines and neurotrophic factors can markedly influence synaptic transmission and plasticity upon acute or chronic application. Moreover, many of the molecular alterations observed in the schizophrenic brain are consistent with abnormalities in cytokine and neurotrophic factor regulation of these molecules. In this review, we summarize these molecular pathology findings for schizophrenia and highlight the neurodevelopmental activities of cytokines and neurotrophic factors that may contribute to the etiology or pathology of this illness.

Effects of antipsychotic drugs on cholecystokinin and preprotachykinin (substance P) mRNA expression in the rat hippocampal formation

To assess the involvement of substance P (SP) and cholecystokinin (CCK) in the effects of antipsychotic drugs, preprotachykinin-A (PPT-A) and CCK mRNA expression was studied in the hippocampal formation using in situ hybridisation following 21 daily i.p. injections with the typical antipsychotic drug haloperidol (1 mg/kg) and the atypical drug clozapine (15 mg/kg). PPT-A mRNA levels were increased in the hippocampal CA3 subregion and in the entorhinal cortex after haloperidol, whereas a decrease was observed in the CA1 after clozapine. CCK mRNA levels increased in the CA1, the entorhinal cortex and in hilus, following both haloperidol and clozapine. It is suggested that earlier findings of increased SP levels in the hippocampal formation of schizophrenics may be a consequence of haloperidol treatment and that reduced hippocampal CCK and CCK mRNA levels found earlier in schizophrenics do not result from antipsychotic drug treatment. These results are consonant to the hypothesis that increased cortical CCK transmission may be beneficial in the treatment of psychosis.

Cholecystokinin, beta-endorphin and vasoactive intestinal peptide in peripheral blood mononuclear cells of drug-naive schizophrenic patients treated with haloperidol compared to healthy controls

Cholecystokinin (CCK), beta-endorphin (BE), and vasoactive intestinal peptide (VIP) in peripheral blood mononuclear cells from 30 drug-naive schizophrenics compared to 22 healthy controls were studied. Patients were evaluated with the Brief Psychiatric Rating Scale (BPRS), the Scale for the Assessment of Positive Symptoms (SAPS) and the Scale for the Assessment of the Negative Symptoms (SANS) at baseline (TO), and after four weeks (T4) in nine patients who were subsequently treated with haloperidol (HL). Neuropeptide concentrations in peripheral blood mononuclear cells (PBMC) were measured at TO and, for the treated patients, at T4. There was a negative correlation between CCK and SANS baseline scores and a trend for patients who responded poorly to HL (i.e. patients with a prevalence of negative symptomatology) to have lower CCK basal values.

Cholecystokinin and psychiatric disorders : role in aetiology and potential of receptor antagonists in therapy

Cholecystokinin (CCK) is one of the most abundant neuropeptides in the brain. It is found in the highest levels in cortical and limbic structures and also in the basal ganglia. Two subtypes of CCK receptors have been described in the brain and gastrointestinal tissues. CCK(A) (alimentary subtype) receptors are mainly located in the gastrointestinal tract, regulating secretion of enzymes from the pancreas and emptying of the gallbladder. However, CCK(A) receptors are also found in several brain regions, with the highest densities in structures poorly protected by the haematoencephalic barrier (the area postrema, nucleus tractus solitarius and hypothalamus). The distribution of CCK(B) (brain subtype) receptors overlaps with the localisation of CCK and its mRNA in different brain areas, with the highest densities in the cerebral cortex, basal ganglia, nucleus accumbens and forebrain limbic structures.Both subtype of CCK receptor belong to the guanine nucleotide-binding protein-(G protein)-linked receptor superfamily containing 7 transmembrane domains. Signal transduction at CCK receptors is mediated via G(q) protein-related activation of phospholipase C and the formation of inositol 1,4,5-triphosphate (IP(3)) and 1,2-diacylglycerol (DAG). Recent cloning of CCK(A) and CCK(B) receptors has shown that mRNA for both receptors is distributed in the same tissues as established in radioligand binding and receptor autoradiography studies, with few exceptions.The existence of multiple CCK receptors has fuelled the development of selective CCK(A) and CCK(B) receptor antagonists. These antagonists belong to distinct chemical groups, including dibutyryl derivatives of cyclic nucleotides, amino acid derivatives, partial sequences and derivatives of the -COOH terminal sequence heptapeptides of CCK, benzodiazepine derivatives, 'peptoids' based on fragments of the CCK molecule, and pyrazolidinones. At the present time, the compounds of choice for blockade of the CCK(A) receptor are lorglumide, devazepide and lintitript (SR27897). L-365,260, CI-988, L-740,093 and LY288513 are the drugs most widely used to block CCK(B) receptors.Studies with CCK antagonists (and agonists) in animals and humans suggest a role for CCK in the regulation of anxiety and panic. The administration of CCK agonists [ceruletide (caerulein), CCK-4, pentagastrin] has an anxiogenic action in various animal models and in different animal species. However, the anxiogenic action of CCK agonists is restricted to nonconditioned (ethological) models of anxiety, with very limited activity in the 'classical' conditioned models. Pharmacological studies have revealed that CCK(B) receptors are the key targets in the anxiogenic action of CCK agonists. Nevertheless, CCK(B) antagonists displayed very little activity, if any at all, in these models, but strongly antagonised the effects of CCK(B) agonists. The anxiogenic/panicogenic action of CCK(B) agonists (CCK-4, pentagastrin) is even more pronounced in human studies, but the effectiveness of CCK(B) antagonists as anxiolytics remains unclear. Clinical trials performed to date have provided inconclusive data about the anxiolytic potential of CCK(B) receptor antagonists, probably because of limiting pharmacokinetic factors.The results of some animal experiments suggest a role for CCK in depression. The administration of CCK(B) antagonists causes antidepressant-like action in mouse models of depression. However, human studies replicating this result have yet to be carried out.A prominent biochemical alteration in schizophrenia is a reduction of CCK levels in the cerebral cortex. This change may be related to the loss of cortical neurons, due to the schizophrenic process itself. In animal studies (mainly in mice), administration of CCK agonists and antagonists has been shown to be effective in several models, reflecting a possible antipsychotic activity of these drugs. However, the data obtained in human studies suggest that CCK agonists and antagonists do not improve the symptoms of schizophrenia. Taking into account the reduced levels of CCK and its receptors found in schizophrenia, treatments increasing, but not blocking, brain CCK activity may be more appropriate.

Abnormal cholecystokinin mRNA levels in entorhinal cortex of schizophrenics

Limbic cortical regions, including anterior cingulate cortex (ACC), prefrontal cortex (PFC) and entorhinal cortex (ERC), have been implicated in the neuropathology of schizophrenia. Glutamate projection neurons connect these limbic cortical regions to each other, as well as to the terminal fields of the striatal/accumbens dopamine neurons. Subsets of these glutamate projection neurons, and of the GABA interneurons in cortex, contain the neuropeptide cholecystokinin (CCK). In an effort to study the limbic cortical glutamate projection neurons and GABA interneurons in schizophrenia, we have measured CCK mRNA with in situ hybridization histochemistry in postmortem samples of dorsolateral (DL)PFC, ACC and ERC of seven schizophrenics, nine non-psychotic suicides and seven normal controls. CCK mRNA is decreased in ERC (especially layers iii vi) and subiculum in schizophrenics relative to controls. Cellular analysis indicates that there is a decrease in density of CCK mRNA in labelled neurons. In so far as ERC CCK mRNA is not reduced in rats treated chronically with haloperidol, this decrease in schizophrenics does not appear to be related to neuroleptic treatment. In contrast, in DLPFC, where schizophrenics do not differ from normals, the suicide victims have elevated CCK mRNA (especially in layers v and vi), and increased cellular density of CCK mRNA, relative to both normals and schizophrenics. These results lend further support for the involvement of ERC and hippocampus in schizophrenia, suggesting that neurons that utilize CCK may be particularly important. Similarly, an increase in CCK mRNA levels in the PFC of suicides adds to a growing body of evidence implicating this structure in this pathological state. In so far as CCK is co-localized with GABA or glutamate in cortical neurons, both of these neuronal populations need to be studied further in schizophrenia and suicide.

Substantia innominata: a notion which impedes clinical-anatomical correlations in neuropsychiatric disorders

Comparative neuroanatomical investigations in primates and non-primates have helped disentangle the anatomy of the basal forebrain region known as the substantia innominata. The most striking aspect of this region is its subdivision into two major parts. This reflects the fundamental organizational scheme for this portion of the forebrain. According to this scheme, two major subcortical telencephalic structures, i.e. the striatopallidal complex and extended amygdala, form large diagonally oriented bands. The rostroventral extension of the pallidum accounts for a large part of the rostral subcommissural substantia innominata, while the sublenticular substantia innominata is primarily occupied by elements of the extended amygdala. Also dispersed across this region is the basal nucleus of Meynert, which is part of a more or less continuous collection of cholinergic and non-cholinergic corticopetal and thalamopetal cells, which stretches from the septum diagonal band rostrally to the caudal globus pallidus. The basal nucleus of Meynert is especially prominent in the primate, where it is sometimes inappropriately applied as a synonym for the substantia innominata, thereby tacitly ignoring the remaining components. In most mammals, the extended amygdala presents itself as a ring of neurons encircling the internal capsule and basal ganglia. The extended amygdala may be further subdivided, i.e. into the central extended amygdala (related to the central amygdaloid nucleus) and the medial extended amygdala (related to the medial amygdaloid nucleus), which generally form separate corridors both in the sublenticular region and along the supracapsular course of the stria terminalis. The extended amygdala is directly continuous with the caudomedial shell of the accumbens, and to some extent appears to merge with it. Together the accumbens shell and extended amygdala form an extensive forebrain continuum, which establishes specific neuronal circuits with the medial prefrontal-orbitofrontal cortex and medial temporal lobe. This continuum is particularly characterized by a prominent system of long intrinsic association fibers, and a variety of highly differentiated downstream projections to the hypothalamus and brainstem. The various components of the extended amygdala, together with the shell of the accumbens, are ideally structured to generate endocrine, autonomic and somatomotor aspects of emotional and motivational states. Behavioral observations support this proposition and demonstrate the relevance of these structures to a variety of functions, ranging from the various elements of the reproductive cycle to drug-seeking behavior. The neurochemical and connectional features common to the accumbens shell and the extended amygdala are especially relevant to understanding the etiology and treatment of neuropsychiatric disorders. This is discussed in general terms, and also in specific relation to the neurodevelopmental theory of schizophrenia and to the neurosurgical treatment of neuropsychiatric disorders.

The elusive nature of cerebellar somatostatin receptors: studies in rat, monkey and human cerebellum

The pharmacological profile and localization of somatostatin (SRIF) receptors were determined in rat, monkey and human cerebellum. In rat cerebellar cortex, low sst1/sst4, intermediate sst2 and very high sst3 receptor mRNA levels were found. sst1 mRNA was also expressed in the deep cerebellar nuclei. [125I]Tyr3-octreotide binding sites in cerebellar membranes correlated with recombinant sst2, but not with sst5 or sst3 receptors and were found in the molecular layer of the cerebellum. [125I]CGP 23996 (in Na(+)-buffer) binding in rat cerebellum correlated with sst1 or sst4, but not with sst2, sst3 or sst5 receptor binding. Similar data were obtained in rhesus monkey cerebellum. mRNAs for all five receptors were found in the granule cell layer of the human cerebellum and/or in the dentate nucleus. [125I]Tyr3-octreotide binding was strong in the molecular layer and correlated with that of recombinant sst2 receptors, but not with sst3 or sst5 receptors. [125I]CGP 23996 (in Mg(++)-buffer) binding was heterogeneous (about 75%, to sst2 and 25% to sst1 and/or sst4 receptors). The molecular and granular layers were equally and the dentate nucleus strongly labeled. Thus, SRIF receptors of the sst2, sst1 and/or sst4 subtype are presnt in the rat, monkey and human cerebellum. In the latter two species, the sst2 type appears to be predominant. Surprisingly, the high expression of sst3 receptor mRNA is not supported by radioligand binding data in any of the species studied. The reason for this discrepancy remains to be elucidated.

Status of somatostatin receptor messenger RNAs and binding sites in rat brain during kindling epileptogenesis

In situ hybridization histochemistry with somatostatin sst1-sst5 receptor messenger RNA-selective oligoprobes and quantitative receptor autoradiographic binding studies using [125I]Tyr3-octreotide, [Leu2,D-Trp22,125I-Tyr25]somatostatin-28 and [125I]CGP 23996 ([125I]c[Asn-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Tyr-Thr-Ser]) were performed to determine the level of expression of somatostatin receptor messenger RNA and receptor binding sites in the hippocampal formation, limbic system and cerebral cortex of adult rats electrically kindled in the dorsal hippocampus. In control rats (implanted with electrodes but not electrically stimulated), the somatostatin-1 receptor-selective [125I]Tyr3-octreotide and the non-subtype-selective [Leu3,D-Trp22,125I-Tyr25]somatostatin-28 preferentially labelled the strata oriens and radiatum of the CA1 subfield of the hippocampus, the molecular layer of the dentate gyrus, the subiculum and presubiculum of the hippocampal formation, the inner layer of the frontal cortex, and the lateral and basolateral nuclei of the amygdala. The non-subtype-selective radioligand [125I]CGP 23996 (in 5 mM Mg2+ buffer) preferentially labelled the strata oriens and radiatum of the CA1 subfield of the hippocampus, the subiculum and the basolateral nucleus of the amygdala. Under conditions where primarily somatostatin-2 receptors were labelled, [125I]CGP 23996 (in 120 mM Na+ buffer) showed strong binding in the strata oriens and radiatum of the CA1 subfield of the hippocampus and the frontal cortex, whereas the dentate gyrus, subiculum and amygdala showed only weak signals. During and after kindling, no significant differences were observed between the ipsi- and contralateral sides of the hippocampus. A significant decrease (about 40%) of somatostatin receptor binding sites was observed in the molecular layer of the dentate gyrus with all radioligands (except [125I]CGP 23996 in Na+ buffer, which did not label this area) at stage 2 (pre-convulsive stage) and one week, but not one month, after stage 5 (generalized motor seizures). In contrast to somatostatin receptor binding, no alterations of the messenger RNA levels for sst1-sst5 receptors were found either at stage 2 or at stage 5. Similarly, no changes in receptor binding or messenger RNA levels were observed in the brain of rats which experienced a single afterdischarge. The present study shows a significant and selective decrease of somatostatin-1 receptor binding sites in the dentate gyrus of kindled rats. This is part of the plastic changes induced by kindling and may contribute to the increased sensitivity for the induction of generalized seizures during kindling.

Localization and pharmacological characterization of somatostatin recognition sites in the human cerebellum

Radioligand binding studies were performed in membranes of human cerebellum using [125I][Tyr3]octreotide also known as [125I]204-090, [125I]LTT-SRIF-28 ([Leu8, D-Trp22, 125I-Tyr25]SRIF-28) and [125I]CGP 23996 ([125I]c[Asu-Lys-Asn-Phe-Trp-Lys-Thr-Tyr-Thr-Ser]) to characterize the nature of cerebellar somatostatin receptors. Saturation experiments performed with [125I]204-090 suggest the presence of a single class of binding sites with high affinity: Bmax = 55.7 +/- 9.7 fmol/mg protein, pKd = 9.57 +/- 0.04. The pharmacological profile of [125I]204-090 and [125I]LTT-SRIF-28 labelled sites in human cerebellar membranes was overlapping (correlation coefficient r = 0.998) and correlated very significantly with that of recombinant human sst2 receptors (r = 0.987). By contrast, there was very little correlation with those of recombinant human sst3 (r = 0.208) or human sst5 receptors (r = 0.547). In contrast to [125I]204-090 or [125I]LTT-SRIF-28 binding, [125I]CGP 23996 binding (in 5 mM MgCl2 buffer) in cerebellar membranes was heterogeneous as indicated by biphasic competition curves produced by sst2 receptor selective ligands such as seglitide or octreotide. The pharmacological profile of the major component was closely correlated with that of human sst2 receptors (r = 0.989), whereas the minor component correlated equally well with human sst1 or sst4 receptors (r = 0.902 and 0.941, respectively). In vitro autoradiographic studies performed in cerebellar slices using [125I]204-090 and [125I]LTT-SRIF-28 demonstrated the presence of binding sites predominantly in the molecular layer, whereas weaker labelling was detected in the granular layer. The distribution of sites labelled by both radioligands was very similar. Using [125I]CGP 23996 (in 120 mM NaCl buffer), no clear difference between labeling of the molecular and granular layers was detectable; the dentate nucleus demonstrated binding sites for [125I]CGP 23996, in contrast to the very low level of binding observed with both, [125I]204-090 and [125I]LTT-SRIF-28. Together, the present data demonstrate the presence of SRIF receptors in the adult human cerebellar cortex which are, for the major population, best characterized as sst2. The SRIF receptors in the minor populations of the cerebellar cortex and the dentate nucleus most probably represent sst1 and/or sst4 sites.

Changes in cholecystokinin mRNA expression in methamphetamine-induced behavioral sensitization

Neuropeptide cholecystokinin (CCK) mRNA was measured in the rat brain subchronically treated with methamphetamine (MAP). Male Wistar rats were injected daily with MAP (3 or 6 mg/kg, i.p., once a day) or saline for 14 days. Progressive reinforcement was observed in MAP-induced stereotyped behaviors. After 7 or 14 days of discontinuation, the rats were decapitated and the brains were prepared for Northern blot analysis using 32P-labeled cDNA probes. Northern blot analysis revealed that the levels of CCK mRNA in the frontal cortex and the hippocampus of 3 or 6 mg/kg MAP-treated rats were significantly decreased, compared to the saline-treated controls. These findings indicate that the alteration in CCK mRNA levels in the frontal cortex and the hippocampus of MAP-treated rats persisted for at least 2 weeks and might be involved in the expression of MAP-induced long-lasting behavioral sensitization (reverse tolerance).

Two faces of cholecystokinin: anxiety and schizophrenia

It has been suggested that cholecystokinin (CCK), a gut-brain peptide found in high concentrations in the mammalian brain, might be implicated in the neurobiology of anxiety and panic disorder. The administration of CCK tetrapeptide induced panic attacks analogous to spontaneous ones in patients suffering from panic disorder and to a lesser degree in healthy volunteers. In animal models of anxiety, the pretreatment with CCK agonists and antagonists produced, respectively, anxiogenic- and anxiolytic-like action on the exploratory paradigms. On the other hand, CCK could also play a role in the pathophysiology of schizophrenia. The administration of CCK agonists (caerulein, CCK-8s) to rodents results in behavioural effects analogous to those of antipsychotic drugs. However, CCK agonists lack any activity in rodent behavioural models to reveal antipsychotic drugs. A significant reduction of CCK concentration and CCK receptors has been shown in cortical and limbic structures of patients suffering from schizophrenia. Nevertheless, administration of CCK agonists to these patients does not effect their symptoms. Two major conclusions should be drawn: first, CCK is involved in the neurobiology of anxiety; second, changes in the CCK system in schizophrenia could be linked to a cortical neurodegeneration related to this disease.

Cholecystokinin messenger RNA deficit in frontal and temporal cerebral cortex in schizophrenia

No consistent markers of pathology have been established yet in schizophrenia, although abnormalities in frontal and temporal structures are indicated from positron emission tomography (PET) studies. We have used in situ hybridization to investigate functional changes focusing on the quantitation of cholecystokinin (CCK) mRNA, whose product has been shown to be depleted in schizophrenia. CCK mRNA and G(o) alpha-subunit mRNA were measured in eight schizophrenic and eight control subjects matched for age and postmortem delay. The study revealed a marked decrease in CCK mRNA of 83% in frontal cortex (BA10) and 63% in superior temporal cortex (BA22) in schizophrenia with no change in G(o) alpha-subunit mRNA in either region. This study was extended to a further series of eight patients to determine the reproducibility of this effect and to quantitate laminar changes in CCK mRNA. Quantitation of CCK mRNA in inner cortical layers (layer V/VI) was carried out in frontal and temporal cortex in comparison with G(o) alpha-subunit mRNA, which is also concentrated in this region; this study showed a similar selective decrease in CCK mRNA in frontal and temporal cortex of 47% and 51%, respectively. A confirmatory decrease in CCK mRNA was also obtained by slot blot analysis of CCK mRNA in tissue extracts of frontal cortex by reference to levels of beta-tubulin mRNA, CCK mRNA:beta-tubulin mRNA was significantly decreased (67%) in schizophrenic tissue compared to control tissue. There was no significant correlation of CCK mRNA loss with neuroleptic treatment or duration of illness.

Cerebrospinal fluid somatostatin concentrations in schizophrenia and schizoaffective disorder: the effects of antipsychotic treatment

The authors examined the effects of antipsychotic treatment on cerebrospinal fluid somatostatin like immunoreactivity (CSF SLI) in 14 schizophrenic and 3 schizoaffective patients. There was a modest but significant increase in CSF SLI in 13 out of the 14 schizophrenic patients. In addition, there was a significant positive correlation between duration of treatment and post-treatment CSF SLI concentrations. No differential response was noted in patients also treated with the anticholinergic benztropine.

Autoradiographic localization of CCK-8 binding sites in the rat brain: effects of chronic methamphetamine administration on these sites

The effects of chronic methamphetamine (MAP) administration (at a dose of 4 mg/kg for 14 days) on [3H]pCCK-8 binding sites in the rat brain were investigated by an in vitro quantitative receptor autoradiographic technique. The number of [3H]pCCK-8 binding sites was significantly reduced in layers III and IV of the medial frontal, anterior, and posterior cingulate cortices, in layers II-IV of the retrosplenial cortex, in layers III-VI of the dorsal insular cortex, and in the reticular nucleus of the thalamus, compared to these numbers in a control group of rats that received physiologic saline. Further, chronic methamphetamine administration led to a significant increase in the number of these binding sites in layer I of the entorhinal cortex. These findings indicate the CCK peptides in the limbic lobe may be closely related to the development of the behavioral changes associated with methamphetamine sensitization. In addition, these results provide supporting evidence for the involvement of the limbic system in the pathophysiology of schizophrenia.

Distribution of secretoneurin, a peptide derived from secretogranin II, in rat brain: an immunocytochemical and radioimmunological study

The distribution of secretoneurin, a peptide derived from its precursor secretogranin II by proteolytic processing, was studied in the central nervous system of the rat by immunocytochemistry and radioimmunoassay and compared to the distribution of secretogranin II messenger RNA by using in situ hybridization. With a specific antiserum a distinct staining of fibers and to a lesser extent also of perikarya was observed throughout the central nervous system. A high density of immunoreactive fibers and terminals was found in several brain areas, i.e. the lateral septum, the medial parts of the amygdala, some medial thalamic nuclei, the hypothalamus, habenula, nucleus interpeduncularis, locus coeruleus, nucleus tractus solitarii, the substantiae gelatinosae of the caudal trigeminal nucleus and of the spinal cord. The quantitative distribution as measured by a radioimmunoassay agreed well with the varying densities of immunoreactivity found by immunocytochemistry. The highest concentrations of this peptide were present in the hypothalamus, in particular, in the median eminence and are comparable to those of the most highly concentrated neuropeptides. The distribution of immunopositive perikarya corresponded well with that of secretogranin II messenger RNA obtained by in situ hybridization. The pattern of secretoneurin expression in rat brain was widespread and unique, partially overlapping with established chemical transmitters and neuropeptides. The functional significance of this new brain peptide remains to be established.

A neuroleptic-like effect of ceronapril on latent inhibition

Three experiments that used a latent inhibition procedure to investigate the effects of ceronapril on attentional processes in the rat are reported. Latent inhibition is a behavioural paradigm in which prior exposure to a stimulus with no significant consequences retards subsequent conditioning to that stimulus when it is paired with reinforcement. Latent inhibition reflects a process of learning to ignore, or tune out, irrelevant stimuli, and has been suggested as an animal model of the attentional processes disrupted in the acute phase of schizophrenia. In animals, latent inhibition is disrupted by the administration of low doses of amphetamine and enhanced by the administration of neuroleptics. Ceronapril is an angiotensin converting enzyme inhibitor that has been shown to retard the breakdown of central cholecystokinin. It has been proposed that elevation of cholecystokinin levels in the brain may possess neuroleptic-like properties. We assessed this possibility by determining the effects of ceronapril on latent inhibition using a conditioned emotional response procedure, consisting of three stages: pre-exposure, in which the to-be-conditioned stimulus, a tone, was repeatedly presented without reinforcement; conditioning, in which the pre-exposed stimulus was paired with shock; and test, where latent inhibition was indexed by animals' suppression of licking during tone presentation. In Experiment 1, 20 tone pre-exposures were given, and conditioning consisted of five tone-shock pairings; we assessed the effects of 0.005 mg/kg, 0.05 mg/kg and 0.5 mg/kg ceronapril, compared with vehicle injections. In Experiment 2, five tone pre-exposures were given, and conditioning consisted of two tone-shock pairings: we assessed the effects of 0.05 mg/kg ceronapril, compared with vehicle injections.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional distribution of neuropeptide somatostatin gene expression in the human brain

The regional distribution of mRNA coding for the neuropeptide somatostatin has been studied in the human brain by in situ hybridization histochemistry using 32P-labeled oligonucleotides. We show that somatostatin mRNA-containing neurons are widely distributed in a number of nuclei and grey areas of the human brain, including neocortex, putamen, nucleus caudatus, nucleus accumbens, amygdala, midbrain, medulla oblongata, hippocampal formation, reticular nucleus of the thalamus, and posterior nucleus of the hypothalamus. No significant hybridization signal was observed in the substantia nigra, claustrum, globus pallidus, thalamus, and cerebellum. The topographic localization of neurons containing SOM mRNA in the human brain is in agreement with previous studies using immunocytochemical or radioimmunoassay techniques. These results show that in situ hybridization histochemistry with oligonucleotide probes can be used to map the distribution of neurons expressing SOM mRNA in human postmortem materials.

The diagnostic validity of paraphrenia

It remains a matter of conjecture as to whether a schizophrenia-like syndrome commencing in old age differs from the early-onset disorder in any substantial way. This article reviews both the historical background to the concept of defining paraphrenia as a distinct entity, as well as the current controversies concerning whether it should remain a separate entity: the latter is important as paraphrenia has not been included in the DSM III-R and ICD 10 classification systems. Clinical parameters and aetiological factors relevant to an understanding of the syndrome are discussed under the rubrics of descriptive and construct validity. Of particular importance are the role of cerebral organic factors and the pathoplastic effect of the ageing process and how both interface with the development of psychotic symptoms. Whilst the course of this syndrome has been considered relatively benign, outcome studies have yet to establish consistent features that provide a basis to determine predictive validity.

Deficits in the somatostatin SS1 receptor sub-type in frontal and temporal cortices in Alzheimer's disease

The aim of this study was to evaluate the possible differential alterations of somatostatin (SRIF) receptor sub-types in Alzheimer's disease (AD). Consequently the binding profile of cortical SRIF receptors were examined in normal and AD brains using non-selective ([125I]Tyr0, D-Trp8-SRIF14) and SS1 receptor sub-type-selective ([125I]SMS204-090) radioligands. Maximal binding capacities, but not affinities, were reduced for both ligands in the temporal cortex. In contrast, only the maximal binding capacity of [125I]SMS204-090 was significantly reduced (68%) in the frontal cortex; no alterations were detected using the non-selective probe. This reveals that while the maximal binding capacity of the SS1 receptor sub-type is altered in frontal and temporal cortices in AD, other putative cortical SRIF receptor classes (such as SS2 sites) are not as broadly affected. This could be of significance for eventual therapeutic approaches using SRIF-related analogues.

Merck, Sharp & Dohme Prize for Young Psychopharmacologists: A history of frontal and temporal lobe aspects of the neuropharmacology of schizophrenia

In the past two decades neurobiological research into schizophrenia has seen a shift of emphasis from the dopaminergic pharmacology of subcortical systems to areas of abnormality inferred from direct studies, i.e. frontal cortex and medial temporal lobe. Recent research has tried to integrate morphological abnormalities with neurochemical and pharmacological data. These integrated approaches have uncovered neurochemical systems other than dopamine which are of importance. This approach has led to greater understanding of neurochemical mechanisms associated with these abnormalities and may provide novel approaches for therapeutic intervention.

The bed nucleus-amygdala continuum in human and monkey

The cytoarchitecture and distributions of seven neuropeptides were examined in the the bed nucleus of the stria terminalis (BST), substantia innominata (SI), and central and medial nuclei of the amygdala of human and monkey to determine whether neurons of these regions form an anatomical continuum in primate brain. The BST and centromedial amygdala have common cyto- and chemo-architectonic characteristics, and these regions are components of a distinct neuronal complex. This neuronal continuum extends dorsally, with the stria terminalis, from the BST and merges with the amygdala; it extends ventrally from the BST through the SI to the centromedial amygdala. The cytoarchitectonics of the BST-amygdala complex are heterogeneous and compartmental. The BST is parcellated broadly into anterior, lateral, medial, ventral, supracapsular, and sublenticular divisions. The central and medial nuclei of the amygdala are also parcellated into several subdivisions. Neurons of central and medial nuclei of the amygdala are similar to neurons in the lateral and medial divisions of the BST, respectively. Neurons in the SI form cellular bridges between the BST and amygdala. The BST, SI, and amygdala share several neuropeptide transmitters, and patterns of peptide immunoreactivity parallel cytological findings. Specific chemoarchitectonic zones were delineated by perikaryal, peridendritic/perisomatic, axonal, and terminal immunoreactivities. The results of this investigation demonstrate that there is a neuronal continuity between the BST and amygdala and that the BST-amygdala complex is prominent and discretely compartmental in forebrains of human and monkey.

Distribution of GABA and neuropeptides in the human cerebral cortex. A light and electron microscopic study

Antibodies were used to identify neurons in human frontal and temporal cortex that were immuno-positive to gamma-aminobutyric acid (GABA) and the neuropeptides vasoactive intestinal polypeptide (VIP), substance P (SP) and somatostatin (SOM). Specimens were taken at surgical biopsy and fixed immediately after removal. The results described for both light and electron microscopy were obtained when relatively high concentrations of glutaraldehyde (2.5-3%) were present in the fixative. Specimens were examined from three adults and an infant aged 5 months. GABAergic neurons were present in all cortical layers, with fewest in layers I, deep III and V, and were mainly small, and round or oval. No labelled pyramidal neurons were detected. GABAergic puncta were common in the neuropil, probably representing axonal profiles. VIP-neurons were also found in all layers, including layer I, and were approximately twice as numerous as GABA-cells. SP-positive cells were found throughout the layers, but were sparse in layers I and VI. They were about three times commoner than GABAergic neurons. SOM-reactivity was demonstrated in about the same number of cells as that for SP. Again, this involved all layers, but layer I least. Peptidergic neurons were larger, on the average, than GABAergic cells, and were frequently pyramidal in character. In the infant, the distribution, size and frequency of immunoreactive neurons were similar to those in the adult. However, GABAergic puncta were commoner.