The intracortical distribution of norepinephrine, dopamine and serotonin in the cerebral cortex of the cat

Pneumatically Sprayed Gold Nanoparticles for Mass Spectrometry Imaging of Neurotransmitters

Using citrate-capped gold nanoparticles (AuNPs) for laser desorption ionization mass spectrometry (LDI-MS) is an approach that has demonstrated broad applicability to ionization of different classes of molecules. Here, we show a simple AuNP-based approach for the ionization of neurotransmitters. Specifically, the detection of acetylcholine, dopamine, epinephrine, glutamine, 4-aminobutyric acid, norepinephrine, octopamine, and serotonin was achieved at physiologically relevant concentrations in serum and homogenized tissue. Additionally, pneumatic spraying of AuNPs onto tissue sections facilitated mass spectrometry imaging (MSI) of rabbit brain tissue sections, zebrafish embryos, and neuroblastoma cells for several neurotransmitters simultaneously using this quick and simple sample preparation. AuNP LDI-MS achieved mapping of neurotransmitters in fine structures of zebrafish embryos and neuroblastoma cells at a lateral spatial resolution of 5 μm. The use of AuNPs to ionize small aminergic neurotransmitters in situ provides a fast, high-spatial resolution method for simultaneous detection of a class of molecules that typically evade comprehensive detection with traditional matrixes.

Functional MRI and response inhibition in children exposed to cocaine in utero. Preliminary findings

This study investigated the potential long-term effects of cocaine exposure on brain functioning using fMRI in school-aged children. The sample included 12 children with prenatal cocaine exposure and 12 non-exposed children (8-9 years old). Groups did not differ on IQ, socioeconomic status, or perinatal risk factors. A response inhibition task was administered during an fMRI scan using a 1.5-T MRI system. Task performance did not differentiate groups, but groups were differentiated by patterns of task-related brain activity. Cocaine-exposed children showed greater activation in the right inferior frontal cortex and caudate during response inhibition, whereas non-exposed children showed greater activations in temporal and occipital regions. These preliminary findings suggest that prenatal cocaine may affect the development of brain systems involved in the regulation of attention and response inhibition.

Neurobiological mechanisms for the regulation of mammalian sleep-wake behavior: reinterpretation of historical evidence and inclusion of contemporary cellular and molecular evidence

At its most basic level, the function of mammalian sleep can be described as a restorative process of the brain and body; recently, however, progressive research has revealed a host of vital functions to which sleep is essential. Although many excellent reviews on sleep behavior have been published, none have incorporated contemporary studies examining the molecular mechanisms that govern the various stages of sleep. Utilizing a holistic approach, this review is focused on the basic mechanisms involved in the transition from wakefulness, initiation of sleep and the subsequent generation of slow-wave sleep and rapid eye movement (REM) sleep. Additionally, using recent molecular studies and experimental evidence that provides a direct link to sleep as a behavior, we have developed a new model, the cellular-molecular-network model, explaining the mechanisms responsible for regulating REM sleep. By analyzing the fundamental neurobiological mechanisms responsible for the generation and maintenance of sleep-wake behavior in mammals, we intend to provide a broader understanding of our present knowledge in the field of sleep research.

Effect of partial sensory deprivation on monoaminergic neuromodulators in striate cortex of adult cat

The role of monoaminergic neuromodulators in the reorganization of cortical topography following limited sensory deprivation in the adult cat was investigated. The total concentrations of dopamine, noradrenaline, serotonin and their major metabolites were measured in the visual cortex of both normal control and experimental animals using microbore high-performance liquid chromatography coupled with electrochemical detection. The experimental animals were subjected to a binocular retinal lesion corresponding to the central 10 degrees of vision and killed two weeks post-lesion. The sensory deprivation was confirmed in area 17 by measuring immediate-early gene zif-268 messenger RNA expression. Following the retinal lesion, the total concentrations of noradrenaline and dopamine were significantly higher in the non-deprived cortex of retinal lesion cats than in the deprived cortex of retinal lesion cats and the cortex of normal animals. This pattern follows the release of the excitatory neurotransmitter glutamate under the same conditions. Serotonin levels were significantly lower in the deprived cortex, and its metabolite 5-hydroxyindole-3-acetic acid was significantly higher in the non-deprived cortex than in deprived cortex and normal cortex. From these results, we suggest that the modulation of noradrenaline, dopamine and serotonin is regulated by visual afferent activity.

In utero cocaine-induced dysfunction of dopamine D1 receptor signaling and abnormal differentiation of cerebral cortical neurons

Monoamines modulate neuronal differentiation, and alteration of monoamine neurotransmission during development produces specific changes in neuronal structure, function, and pattern formation. We have previously observed that prenatal exposure to cocaine in a clinically relevant animal model produces increased length of pyramidal neuron dendrites in the anterior cingulate cortex (ACC) postnatally. We now report that cocaine administered intravenously to pregnant rabbits at gestational stages preceding and during cortical histogenesis results in the early onset of hypertrophic dendritic outgrowth in the embryonic ACC. Confocal microscopy of DiI-labeled neurons revealed that the atypical, tortuous dendritic profiles seen postnatally in ACC-cocaine neurons already are apparent in utero. No defects in neuronal growth were observed in visual cortex (VC), a region lacking prominent dopamine innervation. In striking correlation with our in vivo results, in vitro experiments revealed a significant enhancement of spontaneous process outgrowth of ACC neurons isolated from cocaine-exposed fetuses but no changes in neurons derived from visual cortex. The onset of modified growth in vivo is paralleled by reduced D(1A) receptor coupling to its G-protein. These data suggest that the dynamic growth of neurons can be regulated by early neurotransmitter signaling in a selective fashion. Prenatal onset of defects in dopamine receptor signaling contributes to abnormal circuit formation and may underlie specific cognitive and behavioral dysfunction.

Dopaminergic modulation of transcallosal activity of cat motor cortical neurons

The effects of dopamine (DA) and its antagonists on the transcallosal activity of pyramidal tract neurons (PTNs) and non-PTNs in the anesthetized cat motor cortex were studied with iontophoretic applications; dopamine, SCH 23390 (D1 antagonist), sulpiride (D2 antagonist) and haloperidol. Neuronal activity was recorded with a multi-barreled glass microelectrode. Transcallosal neuronal activity was evoked by stimulation of the contralateral motor cortex. The number of spikes thus activated was counted for the control and test conditions after application of each drug: (1) dopamine application decreased the number of spikes evoked by transcallosal stimulation; (2) application of SCH 23390, sulpiride and haloperidol restored these decreased spike numbers to the control level; (3) latency of neuronal response to transcallosal stimulation was not affected by the application of either DA, SCH 23390, sulpiride or haloperidol; and (4) there was no significant difference between PTNs and non-PTNs in the manner of response to DA and its antagonist applications. Our conclusion is that dopamine modulated the transcallosal neuronal response in the cat motor cortex in a suppressive manner. This fact suggested that interhemispheric neuronal communications could be subjected to suppressive modification by the dopaminergic system.

Prenatal effects of drugs of abuse on brain development

Drugs of abuse modify signaling of neurotransmitter systems and intracellular messengers. Recent studies of central nervous system development show that these same neurotransmitters may serve as molecules that regulate specific aspects of cell proliferation, survival, migration, circuit formation and establishment of topography. Moreover, the convergence of neurotransmitter, growth factor and hormone activity on similar intracellular signaling systems suggests the potential for significant interactions among molecular components that regulate development. The application of modern strategies used by developmental and cell biologists to the question of whether prenatal drug exposure alters brain structure and function has led to discoveries of specific, targeted changes. Studies of the mechanisms of drug action that lead to altered neural development are now reality.

New evidence for neurotransmitter influences on brain development

The early appearance of monoamine systems in the developing mammalian CNS suggests that they play a role in neural development. We review data from two model systems that provide compelling new evidence of this role. In one model system-in utero exposure to cocaine-specific and robust alterations are seen in dopamine-rich areas of the cerebral cortex, such as the anterior cingulate cortex: D1 receptor-G protein coupling is greatly reduced, the GABAergic system is altered and pyramidal dendrites undergo excessive growth. In a second model system-a transgenic mouse line in which the gene that encodes monoamine oxidase A (MAOA) is disrupted, resulting in excessively high 5-HT levels-barrels fail to form in the developing somatosensory cortex. Both models reveal the effects of very early manipulation of monoamines on forebrain development, and the long-term anomalies that persist into adulthood.

Visual evoked cortical responses and electroretinograms following implantation of human fetal mesencephalon to the right caudate nucleus in Parkinson's disease

Pattern electroretinograms and visual evoked cortical responses following flash and checkerboard pattern reversal stimulation were performed in 7 patients with advanced Parkinson's disease before and after implantation of human fetal ventral mesencephalon to the head of the right caudate nucleus. Six to nine months following surgery there was bilateral enhancement of flash-evoked response amplitudes. Electroretinogram measurements were unchanged. Individual increases in amplitude and decreases in latency were seen following pattern stimulation which were not statistically significant. A relationship between change in dyskinesia, and change in checkerboard pattern stimulation amplitude at 2.4 cycles per degree suggests that amplitude effects at this stimulus frequency are mediated via altered dopaminergic receptor status in the grafted hemisphere. This may be relevant to the mechanisms leading to generalised clinical improvements following this grafting technique.

The relationship of pineal calcification to cortical atrophy in schizophrenia

Several recent computed tomographic (CT) studies have provided evidence for structural cerebral abnormalities in schizophrenia. CT scan findings included enlargement of the lateral cerebral ventricles, cortical atrophy, third ventricular dilatation, ventricular asymmetry, and cerebellar atrophy. In addition, there is increasing data to suggest that abnormal pineal melatonin functions are associated with the pathophysiology of schizophrenia. To explore further the relationship of the pineal gland to the pathophysiology of schizophrenia and its specific association with structural abnormalities, we investigated: (a) the relationship of pineal calcification (PC) to computerized tomographic (CT) scan measurements of cortical and subcortical atrophy in 41 chronic schizophrenic patients, and (b) the relationship of PC size to CT scan measurements and cortical and subcortical atrophy in 51 chronic schizophrenic patients. Results of the first study revealed that the presence of PC was significantly associated with measurements of prefrontal cortical atrophy (p less than .01), while there was no association with measurements of parieto-occipital atrophy, sulcal prominence, or ventricular brain ratio (VBR). These findings support the notion that the various structural brain abnormalities in schizophrenia may reflect different pathological processes and that abnormal pineal melatonin functions may be associated with the pathophysiology of prefrontal cortical atrophy. In addition, since some clinical facets of schizophrenia covary with frontal lobe dysfunction, our findings highlight the significance of abnormal pineal functions for the pathophysiology of schizophrenia. In the second study we found a significantly higher prevalence of pathologically enlarged PC (i.e., greater than 1 cm in diameter) in schizophrenia as compared to controls of similar age. In addition, we found a significant association between CT scan measurements of cortical atrophy and pathologically enlarged PC size (p less than .05). By contrast, PC size was unrelated to VBR. These findings demonstrate a specific association between pathologically enlarged PC and cortical atrophy in schizophrenia. The implications of these findings to the pathophysiology of schizophrenia and, specifically, to the morphological abnormalities that accompany the disease are discussed.

Distribution of monoamines and metabolites in rabbit neostriatum, hippocampus and cortex

The monoamines noradrenaline (NA), dopamine (DA), adrenaline (AD) and 5-hydroxytryptamine (5-HT) were assayed in the putamen (PUT), the lateral (lCAU) and medial (mCAU) portions of the caudate, the dorsal (dHIP) and ventral (vHIP) hippocampus, as well as in four cortical areas, i.e., anterior cingulate (CIN), entorhinal-piriform (EnPi), sensorimotor (SSC; somatosensory) and primary visual (VIS). The use of an HPLC procedure enabled us to perform these measurements in microdissected samples and to assay as well monoamine metabolites. The DA levels were highest in the neostriatum, moderate in the EnPi and CIN and very low in the SSC, VIS and hippocampus. The distribution of NA was more uniform, although higher concentrations were measured in the neostriatum, hippocampus and EnPi. The largest amounts of 5-HT were in the EnPi, while moderate concentrations were found in the other regions. The ratios between the neurotransmitters and their metabolites were used as an index of turnover and indicate that the terminal fields of the monoamine systems are heterogenous within the neostriatal, hippocampal and cortical subdivisions.

Comparative distributions of dopamine D-1 and D-2 receptors in the cerebral cortex of rats, cats, and monkeys

The distributions and laminar densities of cerebral cortical dopamine D-1 and D-2 receptors were studied in rats, cats, and monkeys. Distributions were determined by using alternate, adjacent tissue sections processed for D-1 and D-2 receptor subtypes and compared to an adjacent, nearly adjacent, or similar sections stained for Nissl substance. [3H]-SCH 23390 and [3H]-spiroperidol (in the presence of 100 nM mianserin) were used to label the D-1 and D-2 receptors, respectively. The regional distribution and laminar density of dopamine receptors were determined by in vitro quantitative autoradiography and video densitometry of selected isocortical and peri-allocortical regions. Granular (prefrontal, primary somatosensory, and primary visual), agranular (primary motor and anterior cingulate), and limbic (entorhinal and perirhinal) cortices were examined. Where possible, homologous areas among the species were compared. The D-1 receptor was present in all regions and laminae of the cerebral cortex of rats, cats, and monkeys. The regional densities for the D-1 receptor were higher in the cat and monkey than in the rat. The rat D-1 receptor displayed a relatively homogeneous laminar pattern in most regions except that the deeper laminae (V and VI) contained more receptors than the superficial layers. The cats and monkeys, however, had distinctly heterogeneous laminar patterns in all regions of cortex that varied from one region to another and were quite different from that seen in the rat. The cats and monkeys had highest densities of the D-1 receptor in layers I and II and lowest densities in layers III and IV, whereas layers V and VI were intermediate. The density of D-1 receptors was greater than the density of D-2 receptors in all regions and laminae of cerebral cortex of the cat and monkey and greater in most regions and laminae of the rat cerebral cortex. The D-2 receptor was also distributed in all regions of the cerebral cortex of rats, cats, and monkeys. The D-2 receptor was very homogeneous in its regional distribution and laminar pattern compared to the D-1 receptor in all 3 species. The D-2 receptor was denser in the superficial layers (I and II) of the cortex than in the deeper layers in the rats, but more homogeneous in the different laminae of the cat and monkey cerebral cortex. The rat cortical D-2 receptor exceeded the D-1 receptor in restricted laminae of selective regions.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of dopamine on pial arteriolar diameter and CSF prostanoid levels in piglets

We examined effects of topically applied dopamine on pial arteriolar diameter and CSF prostanoid levels in newborn pigs. Vascular responses were determined using the closed cranial window technique and intravital microscopy, and prostanoids were determined by radioimmunoassay. Topical application of dopamine did not change arteriolar diameter at 10(-7)-10(-5) M, but constricted arterioles at 10(-4) (16%) and 10(-3) M (30%). Intravenous administration of indomethacin (5 mg/kg) did not alter this constriction. In addition, CSF prostanoid levels did not increase in response to application of dopamine except for a modest increase of prostaglandin E2 at 10(-3) M. We conclude that dopamine is a constrictor at high doses of piglet pial arterioles and that this response is not modified by endogenous prostanoids.

Evidence for a dopaminergic innervation of cat primary visual cortex

Experiments have been conducted to determine whether dopamine fulfills the criteria to be considered as a neurotransmitter in cat primary visual cortex. N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine, a neurotoxin with high selectivity for noradrenergic terminals, was administered into kitten cerebral ventricles. Two weeks later, the concentration of norepinephrine in visual cortex was reduced to 15% of control while dopamine and serotonin were not depleted. Receptor binding assays with [3H]SCH 23390 showed that membranes prepared from cat primary visual cortex contain a binding site that has the properties of a D1 receptor. This site was localized by autoradiography to two bands, one in layer VI and the second in upper layers of visual cortex. A dopamine-stimulated adenylate cyclase activity was demonstrated that was inhibited by SCH 23390 but not by alprenolol. Norepinephrine was shown to stimulate adenylate cyclase activity through both a beta-noradrenergic receptor and a D1 receptor. Binding assays with [3H]spiperone indicated that D2 dopamine receptors are absent from cat visual cortex or present in very low amounts. Taken together these results strongly suggest the existence of a dopamine innervation of cat primary visual cortex. The neurotoxin experiments show that some of the dopamine in cat visual cortex is not in noradrenergic terminals while the receptor assays demonstrate the presence of D1 receptors functionally linked to the synthesis of cyclic 3',5'-adenosine monophosphate. The demonstration of a dopaminergic innervation in cat primary visual cortex is also relevant to the interpretation of data on the involvement of catecholamines in developmental plastic phenomena.

Serotoninergic innervation of the cat cerebral cortex

Serotoninergic axons in the cat cerebral cortex were demonstrated immunohistochemically with a monoclonal antibody to serotonin (5-HT). Three types of 5-HT axons are distinguished at the light microscopic level by differences in their morphology. Small varicose axons are fine (less than 0.5 micron) and bear fusiform varicosities that are generally less than 1 micron in diameter. These axons extend throughout the width of the cortex and branch frequently, giving rise to widely spreading collaterals. Nonvaricose axons are smooth, show a relatively large and constant caliber (about 1 micron), travel in straight, horizontal trajectories, and branch infrequently. Large varicose axons are distinguished by large round or oval varicosities (1 micron or more in diameter) borne on fine-caliber fibers. These axons often form basket-like arbors around the somata of single neurons. In the simplest basket-like arbors, several large, round varicosities from a small number of axons contact the soma. In complex baskets intertwining collaterals contact the soma and apparently climb along and outline the cell's major dendrites. The patterns revealed by the climbing axons suggest that a variety of nonpyramidal cell types selectively receive dense 5-HT innervation. Serial reconstructions of the 5-HT axons within the cortex show that the large varicose axons arise as infrequent collaterals from the nonvaricose axons. A single nonvaricose parent axon gives rise to several large varicose axon collaterals that may contribute to different basket-like arbors. Conversely, a single basket-like arbor may be formed by large varicose axon collaterals from more than one nonvaricose parent axon. The small varicose axons do not appear to be related within the cortex to either the nonvaricose or large varicose axon types. The results support the hypothesis that the 5-HT projection to the cortex is organized into two subsystems, one of which may exert widespread influence in the cortex via highly divergent branches, while the other, with a more restricted distribution, acts on specific classes of cortical neurons.

Light and electron microscopic immunocytochemical analysis of the serotonin innervation of the rat visual cortex

The serotonin afferents of the rat visual cortex were examined immunocytochemically at the light and electron microscopic levels. Immunoreactive fibres were typically thin, tortuous and varicose. Occasionally, some thicker fibres were found. The orientation of labelled axons varied according to laminar position, with fibres running parallel to the pial surface present mainly in layers I and VI, and radially oriented fibres prominent in layers II and III. Branches arising from horizontal or radially oriented fibres were seen to form irregularly shaped loops particularly in layers IV and V. The density of innervation and the prevailing axonal orientation in each cortical layer were similar in both coronal and parasagittal planes. The ultrastructural features of serotonin-labelled axon terminals were examined in single and serial ultrathin sections. While in single sections the majority did not exhibit synaptic specializations, extensive serial section analysis showed that virtually all of these terminals were engaged in junctional complexes. Postsynaptic elements were spines and dendritic shafts, including pyramidal cell apical dendrites, with both symmetrical and asymmetrical membrane specializations. In axospinous synapses, the labelled terminals were usually adjacent to unstained axon terminals contacting the same postsynaptic element.

Noradrenergic effects on rat visual cortex: single-cell microiontophoretic studies of alpha-2 adrenergic receptors

The catecholamine noradrenaline has been proposed to modulate the excitability of cortical neurons, and such a regulation may be mediated by specific adrenergic receptors. We characterized, using electrophysiological recordings, the types of responses of single cells in the rat visual cortex (areas 17 and 18) to the iontophoretic application of adrenergic agents. For the majority of spontaneous and visually-driven cells sampled, noradrenaline decreased the firing frequency, and in some cases of visually-driven cells could increase the signal/noise ratio. These effects were also documented after the application of the alpha-2 adrenergic agonists clonidine and oxymetazoline, and could be reduced or blocked by a previous ejection of the specific alpha-2 antagonist idazoxan. The present study supports a role for alpha-2 adrenoceptors in the modulation of sensory inputs to the visual cortex.

Ventromedial mesencephalic tegmental (VMT) projections to ten functionally different cortical areas in the cat: topography and quantitative analysis

The cortical projections of the ventromedial mesencephalic tegmentum (VMT) were studied in the cat by the retrograde transport of wheat germ agglutinin-conjugated HRP (WGA-HRP). The following cortical regions were injected: prefrontal, cingulate, motor, somatic sensory, auditory, primary visual, secondary visual, parasplenial, insular, and entorhinal. Labelled cells in the five component nuclei of the VMT (rostral linear, parabrachial pigmented, central linear, interfascicular, and paranigral nuclei) were counted and the numbers correlated with the total cell populations of the nuclei. In all experiments large numbers of cells were labelled in the VMT, particularly in the rostral linear and parabrachial pigmented nuclei. Following entorhinal cortical injections, significant labelling occurred in the interfascicular and central linear nucleus, although some cells of these nuclei were labelled in every experiment. The cells of the paranigral nucleus remained unlabelled in all experiments. Several hundred VMT cells were labelled in most experiments, over 1000 in the case of the parasplenial and over 2000 in the case of prefrontal injections. The most strongly labelled nucleus was the rostral linear, in which up to 36% of the total cell population could be labelled in a single experiment. These results indicate that the VMT of the cat is a major source of brainstem projections to the cerebral cortex and that all cortical areas are reached by this system. Although the projections to the prefrontal and limbic cortical areas are particularly prominent, there appears to be a consistent and significant projection to all areas. Further, the projection of the VMT to the cortex is topographically organized, indicating that the functional roles of the component nuclei of the VMT may be substantially different.

Ventral tegmental (A10) system: neurobiology. 1. Anatomy and connectivity

The VTA contains the A10 group of DA containing neurons. These neurons have been grouped into nuclei to be found on the floor of the midbrain tegmentum--Npn, Nif, Npbp and Nln rostralis and caudalis. The VTA is traversed by many blood vessels and nerve fibers. Close to its poorly defined borders are found DA (A8, A9, A11) and 5-HT containing neurons (B8). Efferent projections of the VTA can be divided into 5 subsystems. The mesorhombencephalic projects to other monoaminergic nuclei, the cerebellum and a fine projection descends to other tegmental nuclei as far as the inferior olive. Fibers to the spinal cord have not been demonstrated. The mesodiencephalic path projects to several thalamic and hypothalamic nuclei and possibly the median eminence. Functionally important examples are the anterior hypothalamic-preoptic area, N. medialis dorsalis and reuniens thalami. These two subsystems are largely non-dopaminergic. A minor mesostriatal projection is overshadowed by the large mesolimbic projection to the accumbens, tuberculum olfactorium, septum lateralis and n. interstitialis stria terminalis. There are also mesolimbic connections with several amygdaloid nuclei (especially centralis and basolateralis), the olfactory nuclei and entorhinal cortex. A minor projection to the hippocampus has been detected. The mesocortical pathway projects to sensory (e.g. visual), motor, limbic (e.g. retrosplenial) and polysensory association cortices (e.g. prefrontal). Prefrontal, orbitofrontal (insular) and cingulate cortices receive the most marked innervation from the VTA. A more widespread presence of DA in other cortices of rodents becomes progressively more evident in carnivores and primates. Most but not all projections are unilateral. Some neurons project to more than one area in mesodiencephalic, limbic and cortical systems. The majority of these fibers ascend in the MFB. Most areas receiving a projection from the VTA (DA or non-DA) project back to the VTA. The septohippocampal complex in particular and the limbic system in general provide quantitatively much less feedback than other areas. The role of the VTA as a mediator of dialogue with the frontostriatal and limbic/extrapyramidal system is discussed under the theme of circuit systems. The large convergence of afferents to certain VTA projection areas (prefrontal, entorhinal cortices, lateral septum, central amygdala, habenula and accumbens) is discussed under the theme of convergence systems.(ABSTRACT TRUNCATED AT 400 WORDS)

Dopamine in the visual cortex of the cat

The endogenous content of noradrenaline (NA) and dopamine (DA) was determined by radioenzymatic assays in three different areas of the occipital (visual) cortex, in normal cats as well as in DA-deafferented animals. The use of HPLC methodology enabled us to detect and measure in addition two metabolites of DA: 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), thus confirming the existence of a DA innervation in this cortical region.

Sleep and epilepsy

Epileptic mechanisms in the brain are subject to long-duration, time-ordered neuromodulatory processes controlled by endogenous oscillators which are responsible for appropriately phased modulation of various normal physiological processes, including the 24-h sleep/wakefulness cycle and the ultradian 100-min cycle of rapid eye movement/non-rapid eye movement sleep. Both focal and generalized types of epileptiform activity in humans are subject to biorhythmic modulation, and the various modulation patterns observed are in accord with a model which explains these patterns as a consequence of the interaction of two endogenous modulatory processes: one with a period of about 24 h, the other with a period of about 100 min. Differences in the phase angle between the two cyclic processes, determined by time of sleep onset, explain the various modulatory patterns observed. The mechanisms involved in the genesis and elaboration of electrical epileptiform activity in animal models are examined in relation to known processes involved in the physiology of sleep, and compared with data derived from long-term studies of the time distribution of epileptic events in humans. In infantile spasms, clinical seizure activity and the ictal and interictal EEG patterns in relationship to the phases of the sleep cycle, the significant defects in the quality and quantity of sleep in this disorder, and the changes that take place in all of these when seizures are abolished by effective treatment, suggest that pontine mechanisms responsible for the sleep cycle may be involved in the elaboration of infantile spasms and hypsarrhythmia.

Catecholamines and serotonin in the rat central nervous system after 6-OHDA, 5-7-DHT and p-CPA

The norepinephrine (NE), epinephrine (EPI), dopamine (DA) and serotonin (5-HT) contents were measured radioenzymatically in seven anatomically defined regions (frontal cerebral cortex, hippocampus, hypothalamus, midbrain, pons-medulla oblongata, cerebellum and spinal cord) in adult normal animals, after treatment with the tryptophan hydroxylase inhibitor p-chlorophenylalanine (p-CPA), and after the intraventricular administration of either 6-hydroxydopamine (6-OHDA) or 5,7-dihydroxytryptamine (5,7-DHT). The effects of p-CPA seemed not restricted to 5-HT, since reductions in catecholamine (CA) content were detected in several regions. After 5,7-DHT given under desimipramine (DMI) protection, comparable reductions in 5-HT levels were obtained but the changes in CA were less severe than after p-CPA. The neurotoxin 6-OHDA decreased the CA in all regions but also 5-HT content in hippocampus, hypothalamus and pons-medulla. The significance and the interpretation of these changes are discussed in relation to the specificity of the drugs employed, together with an assessment of the local monoamine turnover and the possible functional effects of monoamine interactions in the CNS.

Region-specific distribution of catecholamine afferents in primate cerebral cortex: a fluorescence histochemical analysis

The density, laminar distribution, spatial orientation, and intrahemispheric pathways of norepinephrine (NE)- and dopamine (DA)- containing axons were analyzed in a wide range of cytoarchitectonically distinct areas of cerebral cortex in the adult rhesus monkey by fluorescence histochemistry. Although the boundaries between most areas were rarely sharp, there were marked regional differences in density and distribution of monoamine afferents in different cortical regions. Fibers exhibiting typical DA-like morphology were found only in the temporal and frontal lobes including motor and premotor areas as well as anterior cingulate and prefrontal cortices. In contrast, NE-containing axons were present in all cerebral lobes, with notably high density in the somatosensory area and low numbers in primary visual cortex. Intracerebral distribution was characterized by a network of large preterminal axons coursing both anteroposteriorly and mediolaterally in layer VI and in the subjacent white matter. In most cytoarchitectonic regions examined, catecholamine (CA)-containing axons exhibited a bilaminar distribution into one superficial and one deep fiber band. The location and width of the two dense bands, as well as the orientation and relative density of fibers within them, was region specific. Although fluorescent axons were found at all cortical depths, layers I, and IV usually contained relatively few fluorescent axons while layers II-III and IV-V were often densely innervated. An observation that may reflect a specialization in gyrencephalic brains is the particularly dense CA innervation around sulcal invaginations in all cerebral lobes. The present results confirm previous biochemical evidence of regional heterogeneity in the concentration of DA and NE in the primate neocortex (Brown and Goldman, '77:Brain Res. 124:576-550) an provide the first anatomical demonstration of corresponding differences in the pattern and density of CA innervation in diverse cytoarchitectonic areas in rhesus monkey. These findings raise the possibility of selective targets and functions for CA fibers in different layers and regions of the primate cortex.

Intralaminar neurochemical distributions in human midtemporal cortex: comparison between Alzheimer's disease and the normal

The intralaminar distributions of transmitter and nontransmitter enzyme activities and amino acid levels were determined in the midtemporal cortices from normal individuals and established cases of Alzheimer's disease. In the normal, choline acetyltransferase (CAT) and acetylcholinesterase (AChE) activities were relatively high in the outer cortical layers, particularly, for CAT, in the two granular layers (II and IV). Both activities were reduced in Alzheimer's disease at all, although generally most extensively in the outer and middle layers of the grey matter whereas activities were near normal in the white matter. Further, the enzyme distribution patterns of these cholinergic activities were also disrupted in Alzheimer's disease and the activity of CAT throughout the cortex was generally reduced to that found in the white matter. No such differences in distribution were found for two other enzymes, pseudocholinesterase and lactate dehydrogenase. Assessment of the gamma-aminobutyric acid (GABA) system in the normal revealed a much more extensive intralaminar variation in the enzyme, glutamate decarboxylase, compared with the level of GABA itself. In contrast with the cholinergic enzymes, neither the levels nor intralaminar patterns of GABA were altered in Alzheimer's disease. From an analysis of free amino acids at the different cortical levels, the cortical pattern of glutamic acid in the normal was different from that for GABA, aspartic acid, or nontransmitter amino acids such as alanine. Neither of the putative amino acids, glutamate or aspartate, was altered in Alzheimer's disease. These findings demonstrate the relatively selective nature of microchemical changes occurring in the cortex in Alzheimer's disease and suggest that a functional abnormality in cholinergic input to the outer neocortical layers (I-IV) with predominantly receptive and associative functions may be an important feature of the disease.

Norepinephrine levels in developing pigeon brain: effect of monocular deprivation on the Wulst noradrenergic system

The endogenous level of norepinephrine (NE) was measured in discrete brain areas of the pigeon during post-hatching development. The pontine tegmentum showed the highest NE content, which remained constant during the post-hatching period. On the contrary, the NE content in the Wulst and cerebellum gradually decreased from hatching to 6 days. After this period, the Wulst NE level did not change significantly. In fact, there was no significant difference between NE values at 6 days and those at 6 months of age. In contrast, the difference between the cerebellar NE level at 6 days and that at the adult stage was highly significant. The NE content in the Wulst could be related to noradrenergic afferents originating in the ipsilateral locus coeruleus and substantia grisea centralis, since an electrolytic lesion of the pontine tegmentum caused a 60% reduction in the NE level in the ipsilateral Wulst. In line with the hypothesis that NE plays an important role in cortical plasticity, effects of early monocular deprivation on the Wulst NE content were also observed. After monocular deprivation during the first 6 months of life, the NE level increased by 40% in the Wulst ipsilateral to the deprived eye in comparison to the other side, where the NE level was normal. Monocular deprivation performed in adult animals did not affect the NE content in the Wulst. These results indicate that noradrenergic systems in the Wulst are affected by early, but not late visual deprivation.

Effects of chlorpromazine and promazine on the visual aftereffects of tilt and movement

The effects of chlorpromazine (CPZ) and promazine on the visual aftereffects of tilt and motion were measured. CPZ markedly reduced the strength of both aftereffects, while promazine produced a smaller and not always significant reduction. Control experiments suggested that the effects were produced in the central visual system rather than by several possible peripheral artefacts or by drowsiness. The effects are discussed with reference to the pharmacological activity of the drugs and their influence on the strength of inhibition in the visual cortex, both in normal subjects and in schizophrenic illness.

The development of beta-adrenergic receptors in the visual cortex of the rat

The development of beta-adrenergic receptors in the rat visual cortex was examined and the density of beta-receptors and associated subtypes (beta 1 and beta 2) was compared between visual and non-visual or whole cortical tissues using radioreceptor assays employing [125I]iodohydroxybenzylpindolol and [125I]iodocyanopindolol as ligands. Saturation assays revealed not only similar affinities of beta-receptors for [125I]iodohydroxybenzylpindolol in visual cortical samples at 10, 24 and 160 days after birth but also practically identical saturation curves for visual and non-visual cortical samples at 160 days of age. Displacement of [125I]iodohydroxybenzylpindolol with propranolol in visual cortical membranes at various postnatal ages showed a gradual increase in receptor density from day 4 to day 24 with no change thereafter. No significant differences were observed in the overall density of beta-receptors or in the distribution and density of beta 1 and beta 2-receptors between visual and non-visual or whole cortical samples; however, there was a definite decline in the density of beta-receptors in these samples between 40 and 160 days of age. The results indicate that the developmental pattern of beta-receptor density and the distribution of beta 1 and beta 2-receptors are similar between visual and whole cortical tissues. In addition, the results emphasize the importance of maintaining the dissociation constant at a fixed value when comparing receptor densities between experiments, and also show the utility of employing the high-affinity ligand, [125I]iodocyanopindolol, with a combination of serotoninergic, dopaminergic and alpha-adrenergic antagonists to examine beta-adrenergic receptors in a specific region of the brain. Study of beta-receptors in the visual cortex may be beneficial in elucidating the role of norepinephrine in this region.

Responses of intracellularly recorded cortical neurons to the iontophoretic application of dopamine

Considering that a well-defined dopaminergic projection from the mesencephalic structures to the rat frontal cortex has been demonstrated, the purpose of this research was to study the action of iontophoretically applied dopamine (DA) on intracellularly recorded rat frontal neurons. The stimulation of the substantia nigra (SN) and the ventral tegmental area (VTA) evoked EPSP-IPSP sequences in these cells. About 50% of the tested neurons, widely distributed in all the frontal cortex, responded to DA application and no difference in the response to DA was observed between neurons with monosynaptic inputs and neurons with polysynaptic inputs. The catecholamine depolarized the cell membrane and decreased the firing rate, generally without significant changes in membrane resistance, as already observed in rat and cat striatal cells. In some neurons the decrease of the spikes preceded the membrane depolarization. Considering the complex effect of DA on the electrical properties of these neurons, these results seem to be indicative of a mechanism of action dependent on metabolic changes.

Catecholamines and serotonin in rat frontal cortex after PCPA and 6-OHDA: absolute amounts and ratios

The catecholamines dopamine, epinephrine and norepinephrine, as well as the indoleamine serotonin were measured using radioenzymatic assays, in the frontal cortex of normal rats and of rats in which serotonin synthesis had been inhibited with p-chlorophenylalanine. Besides serotonin, norepinephrine levels were significantly reduced, thus changing the monoamine ratios. To further evaluate these changes, two models of catecholaminergic deafferentation were analyzed, i.e., the massive catecholamine depletion induced by intraventricular 6-OHDA and the more selective norepinephrine deafferentation, obtained by microinjecting 6-OHDA in the dorsal noradrenergic bundle. The results are interpreted in relation to the functional interactions between the catecholamines and between the catecholamines and serotonin.

Noradrenergic and serotonergic fibers innervate complementary layers in monkey primary visual cortex: an immunohistochemical study

Antisera directed against human dopamine beta-hydroxylase or serotonin were used to characterize the noradrenergic and serotonergic innervation patterns within the primary visual cortex of the squirrel monkey. The noradrenergic and serotonergic projections exhibit a high degree of laminar complementarity: layers V and VI receive a dense noradrenergic projection and a very sparse serotonergic projection, whereas layer IV receives a very dense serotonergic projection and is largely devoid of noradrenergic fibers. In addition, the noradrenergic fibers manifest a geometric order that is not so readily apparent in the distribution of serotonergic fibers. These patterns of innervation imply that the two transmitter systems affect different stages of cortical information processing--the raphe-cortical serotonergic projection preferentially innervates the spiny stellate cells of layers IVa and IVc, whereas the ceruleo-cortical noradrenergic projection innervates pyramidal cells.

Altered neuronal responsiveness to biogenic amines in rat cerebral cortex after serotonin denervation or depletion

To further investigate monoaminergic mechanisms in cerebral cortex, responsiveness of cortical neurons to microiontophoretic applications of serotonin (5-HT), dopamine (DA) or noradrenaline (NA) was examined in the frontoparietal region of control, 5,7-dihydroxytryptamine (5,7-DHT)- and p-chlorophenylalanine (PCPA)-treated rats anesthetized with urethane. As a rule, 100 nA applications of either one of these biogenic amines induced marked slowing or total interruption of 'spontaneous' firing overlasting the 30 s period of ejection. Given the large amounts of monoamines ejected, it could be inferred that such microiontophoretic applications produced a maximal activation of receptors. In control rats, the responses to 5-HT, DA and NA were of approximately equal duration (approximately equal to 5 min). Two to 4 weeks after denervation with 5,7-DHT, most neurons (75%) exhibited greatly prolonged responses to 5-HT (approximately equal to 14 min), and marked depressions of firing could be induced by small ejection currents (approximately equal to 2 nA) having little or no effect in the controls. In addition, 85% of the units supersensitive to 5-HT showed considerably shortened responses to DA and NA (approximately equal to 1 min). After 2-14 days of depletion with PCPA, there was no change in the responsiveness to 5-HT in spite of a 91% lowering of cortical 5-HT content equivalent to that measured after denervation. Nevertheless, responsiveness to DA and NA was again diminished in a majority (80%) of the units tested. In control or PCPA-treated rats, acute administration of the 5-HT re-uptake blocker fluoxetine increased the duration of depressions induced by 100 nA applications of 5-HT but did not enhance responsiveness to low ejection currents. This suggested that, after 5-HT denervation, the suppression of re-uptake was mainly responsible for the prolongation of 5-HT responses ('presynaptic' component of supersensitivity), whereas a modification of 5-HT receptors accounted for the greater efficacy of small doses of 5-HT ('postsynaptic' component). Responsiveness to the microiontophoretic application of phenylephrine (PHE), a noradrenergic a-agonist, was comparable with that to NA in PCPA- and 5,7-DHT-treated as well as in control rats. Therefore, the hyposensitivity to DA and NA appeared indicative of a desensitization of catecholamine receptors caused by the absence of 5-HT. Such a desensitization may be viewed as an adaptive change resulting from an increased release of endogenous DA and NA. This interpretation would in turn imply that, normally, 5-HT regulates catecholamine release in the neocortex.

Dynamic changes of serotonin levels during the first visual experience of binocularly deprived kittens

Kittens deprived of pattern vision until the 28th day of life received monocular visual experience for 3, 6, 14, and 75 h. Biphasic response of serotonin was found in the visual cortex. Stimulation for 3 h resulted in an increase of serotonin level whereas at 14 h it produced a decrease. The effects are transient, no longer observable after 75 h stimulation. No changes were observed in somatosensory cortex.

Histochemical evidence for a catecholaminergic (presumably dopaminergic) projection from the ventral mesencephalic tegmentum to visual cortex in the cat

An histochemical technique combining the retrograde transport of horseradish peroxidase (HRP) and catecholamine histofluorescence was used to identify those neurons of the cat's mesencephalic ventromedial tegmentum (VMT) which project to visual cortex. In a region corresponding to the ventral tegmental area-A10 nucleus we identified a group of fluorescent cells which were retrogradely labeled by HRP injections into visual cortex. It is suggested that these cells belong to a hitherto unknown, posterior part of the mesocortical dopaminergic system.

Distribution of catecholamines and serotonin in the rat cerebral cortex: absolute levels and relative proportions

The rat cerebral cortex was dissected in five regions and analyzed for the catecholamines noradrenaline, adrenaline and dopamine, and for the indoleamine serotonin using sensitive radioenzymatic assay methods with thin-layer chromatography. The noradrenaline concentration was highest in the ventral cortex, lateral to the hypothalamus, had intermediate values for the prefrontal, frontal and parietal cortical areas and was lowest in the occipital cortex. Dopamine levels were also highest in the cortex lateral to the hypothalamus, and moderate in the prefrontal and frontal cortical areas, with the lowest values measured for the occipital cortex. The ratios dopamine/noradrenaline further supports the hypothesis that they are independent transmitters. Traces of adrenaline were measured in all regions examined. The serotonin distribution was found to be non-homogeneous, with the highest values for the prefrontal cortex and ventral cortex lateral to the hypothalamus. The functional significance of these amines and their ratios are discussed in relation to their role as putative modulators of cortical neuronal excitability.

An ultrastructural and biochemical analysis of norepinephrine-containing varicosities in the cerebral cortex of the turtle Pseudemys

The fine structure and norepinephrine content of small granular vesicle-containing profiles were studied in normal and norepinephrine-depleted cerebral cortex of the turtle, Pseudemys. The cortex was fixed for electron microscopy with the KMnO4 procedure of Koda and Bloom ('77), while the norepinephrine content was assayed wit the radioenzymatic method of Coyle and Henry ('73). Green fluorescent fibers have been described by Parent and Poitras ('74) as located almost exclusively in the outer half of the molecular layer in turtle cortex. Small granular vesicle-containing profiles are found down to 100 microns below the pial surface, but over 50% lie within 20 microns of the surface. Within the outer 100 microns of cortex, the frequency of labeled varicosities is 1.39/1,000 microns2. The average area of the norepinephrine-containing varicosities is 0.61 microns2, and there is a mean of 18.4 vesicles per single section. The average number of large plus small vesicles in an entire varicosity was estimated to be 72. Synaptic membranes are not well-preserved with KMnO4 fixation, but good examples were found of small granular vesicle-containing profiles forming both symmetrical and asymmetrical membrane differentiations. Only a small percentage of the small granular vesicle profiles were associated with a synaptic membrane differentiation in single sections. When norepinephrine-fiber synapses are seen, they usually share a postsynaptic element with another unlabeled vesicle-containing profile. Normal turtle cortex contains an average norepinephrine concentration of 1.95 micrograms/gr, which is about eight times higher than in rat cortex. The ratio of norepinephrine to dopamine is about 18 to one, suggesting that dopamine is present predominantly in a precursor pool for norepinephrine. Small granular vesicle-containing profiles were eliminated after treatment with reserpine and 6-hydroxydopamine in concentrations that were shown to reduce norepinephrine concentration by 94% and 86%, respectively. The labeled varicosities were partially depleted by midbrain hemisection and by an inhibitor of dopamine-beta-hydroxylase (FLA-63). The norepinephrine-containing varicosities are remarkably coextensive with the distribution of thalamic fibers, both in the total extent of cortex where they are found and in the depth of cortex where they terminate. The results support the idea that there is a close structural and functional association between locus coeruleus and thalamic fibers in cerebral cortex, and the apparent difference in frequency of synapses suggests that each fiber system exerts its influence on cortical cells in a different way.

Characterization and radioautography of [3H]LSD binding by rat brain slices in vitro: the effect of 5-hydroxytryptamine

Binding of D-[3H]lysergic acid diethylamide (LSD) to rat coronal brain slices and its blockade by 5-hydroxytryptamine (5-HT) had characteristics similar to those of brain homogenates in respect of KD, kinetics and reversibility of binding. Radioautography was done on slices that had been incubated in 6 nM [3H] LSD and on adjacent slices incubated in the same concentration of tritiated LSD plus 10(-5) M of 5-HT. Choroid plexus showed densest labeling of [3H] LSD. In neuropil, dense labeling occurred within parts of the hippocampal formation except for fields CA2 and CA3 which were sparsely labeled. All layers of the cortex except the posterior cingulate gyrus were labeled by LSD. 5-HT blocked labeling of choroid plexus, hippocampal formation, septum, pons, medulla and parts of cortex but only reduced labeling of most other structures. LSD binding sites may relate to some of its pharmacological effects.

Serotonin distribution in rat cerebral cortex; radioenzymatic assays with thin-layer chromatography

Serotonin was measured in six different cortical regions of the rat by a specific and sensitive radioenzymatic assay which includes thin-layer chromatography in the last separation step. The indoleamine was found to be unevenly distributed throughout the cortical regions examined; and the highest concentrations were determined for the prefrontal and the occipito-temporal cortex lateral to the hypothalamus. These results correlate with anatomical and electrophysiological studies which support a modulatory role for the serotonin afferent innervation of the cerebral cortex.