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18 recordsLinked to original sources
PubMed1978

Catecholamine innervation of the basal forebrain. III. Olfactory bulb, anterior olfactory nuclei, olfactory tubercle and piriform cortex.

The catecholamine innervation of the olfactory bulb, anterior olfactory nuclei, olfactory tubercle and piriform cortex was studied in the rat using biochemical analysis and fluorescence histochemistry. Biochemical studies demonstrate a moderate norepinephrine (NE) content in all olfactory structures, a high dopamine (DA) content in the olfactory tubercle and a low DA content in the olfactory bulb, anterior olfactory nucleus and piriform cortex. Following locus coeruleus lesions NE content decreases 71% in the olfactory bulb, 82% in the anterior olfactory nucleus, 62% in olfactory tubercle and 77% in piriform cortex...

Amygdala↗
PubMed1977

Cellular events induced in the molecular layer of the piriform cortex by ablation of the olfactory bulb in the mouse.

Cellular events associated with degeneration of the projection of the olfactory bulb to the molecular layer of the piriform cortex of the mouse have been studied with rapid-Golgi and Fink-Heimer impregnations and with the electron microscope. Four classes of axon terminals: s-1, s-d, f-1, and f-d, are differentiated on the basis of whether the synaptic vesicles are spherical or flattened and whether the axoplasm is lightly or darkly stained. The majority of s-1 terminals, the predominant class in sublamina Ia of the molecular layer, degenerate after bulb ablation. Degeneration of axon terminals is associated with dilation and, eventually, degeneration of segments of dendrites in Ia. Both s-1 and s-d terminals contribute to a partial reconstitution of the neuropil of Ia during the weeks after bulb ablation.

Animals↗
PubMed1978

Exploration and avoidance in rats with lesions in amygdala and piriform cortex.

Lesions localized to specific areas of the amygdala and overlying cortex in rats produced differential effects in several behavioral tasks. Three different types of lesions were tested: central, basolateral, and cortex lateral to the amygdala. Lesions restricted to the central nucleus produced increased activity on all parameters studied in an open-field test, but the other two groups were not changed. In one-way active avoidance all three groups with lesions showed deficits. The most pronounced change was observed in the central group. All groups showed the same degree of retention loss, but in forced extinction of one-way active avoidance after retraining, the cortical and basolateral groups were most defective. A fear-reduction hypothesis is proposed for the central lesion. The basolateral and cortical areas may be more specifically involved in passive avoidance behavior.

Amygdala↗
PubMed1978

Association and commissural fiber systems of the olfactory cortex of the rat.

The association and commissural fiber systems arising in the olfactory cortical areas caudal to the olfactory peduncle (the piriform cortex, nucleus of the lateral olfactory tract, anterior cortical nucleus of the amygdala, periamygdaloid cortex and entorhinal cortex) have been studied utilizing horseradish peroxidase as both an anterograde and a retrograde axonal tracer. In the piriform cortex two sublaminae within layer II (IIa and IIb) layer III have been found to give rise to distinctly different projections. Retrograde cell labeling experiments indicate that the association fiber projection from layer IIb is predominatnly caudally directed, while the projection from layer III is predominantly rostrally directed. Cells in layer IIa project heavily to areas both caudal and rostral to the piriform cortex. The commissural fibers from the piriform cortex are largely restricted in their origin to layer IIb of the anterior part of the piriform cortex and in their termination on the contralteral side to the posterior part of the piriform cortex and adjacent olfactory cortical areas. A projection to the olfactory bulb has also been found to arise from cells in layers IIb and III of the ipsilateral piriform cortex, but not in layer IIa. In addition to those from the piriform cortex, association projections have also been found from other olfactory cortical areas. The nucleus of the lateral olfactory tract has a heavy bilateral projection to the medial part of the anterior piriform cortex and the lateral part of the olfactory tubercle (as well as a lighter projection to the olfactory bulb); both the anterior cortical nucleus of the amygdala and the periamygdaloid cortex project ipsilaterally to several olfactory cortical areas. The entorhinal cortex has been found to project to the medial parts of the olfactory tubercle and the olfactory peduncle. The olfactory tubercle is the only olfactory cortical area from which no association fiber systems (instrinsic or extrinsic) have been found to originate. A broad topographic organization exists in the distribution of the fibers from several of the olfactory areas. This is most obvious in the anterior part of the olfactory cortex, in which fibers from the more rostral areas (the anterior olfactory nucleus and the anterior piriform cortex) terminate in regions near the lateral olfactory tract, while those from more caudal areas (the posterior piriform cortex and the entorhinal cortex) terminate in areas further removed, both laterally and medially, from the tract. Projection to olfactory areas from the hypothalamus, thalamus, diagonal band, and biogenic amine cell groups have been briefly described.

Animals↗
PubMedDate not supplied

[Electrophysiological study of the functional connections of the hypothalamus with the forebrain in the tortoise Emys orbicularis].

During stimulation of the posterior hypothalamus, the evoked potentials with short latent periods, high amplitude and poor exhaustion by rhythmic stimulation were recorded in the hippocampal cortex. In the piriform cortex, the evoked potentials exhibited longer latent periods and complex configuration. Less readily the evoked potentials appeared in the neocortex, their latency being very large. During stimulation of the anterior hypothalamus, maximum activity was also localized in the hippocampal cortex. The data obtained indicate close connection between hypothalamic structures and the hippocampal cortex. The latter is presumably the main projectional area for the ascending afferentation from the hypothalamus.

Animals↗
PubMed1979

Regional topography within noradrenergic locus coeruleus as revealed by retrograde transport of horseradish peroxidase.

A hitherto unsuspected degree of regional topographic organization in the noradrenergic nucleus, locus coeruleus, was revealed by the use of retrograde transport of horseradish peroxidase (HRP) from terminal areas receiving noradrenergic innervation. HRP was injected into hippocampus, hypothalamus, thalamus, caudate-putamen, septum, amygdala-piriform cortex, cerebellum and cortex. Successful transport was obtained from all areas, including the caudate-putamen and cerebral cortex. The pattern of HRP positive cells in the ipsilateral locus coeruleus was markedly different depending on the location of the HRP injection. Thus, hippocampal injections labeled cells in the dorsal locus coeruleus but not at all in the ventral tip. Injections of HRP into caudate-putamen or cerebellum labeled the ventral tip along with the rest of the dorsal portion. HRP injections into the septum labeled cells only in the dorsal half of the dorsal locus coeruleus. There thus exists a three tier division of locus coeruleus into the ventral one third, dorsal one third and intermediate one third. A further division was seen in the anterior-posterior plane with HRP injections into the thalamus labeling the posterior pole of locus very intensely but with little transport to more anterior levels; conversely HRP injection into the hypothalamus resulted in intense labeling only in the anterior pole of locus coeruleus. Amygdala-piriform cortex HRP injections revealed a further pattern with very intensely reactive cells scattered sparsely throughout the nucleus. Cortical HRP injections yielded weaker labeling also in occasional, scattered cells. All HRP transport to locus coeruleus was shown to be noradrenergic by degeneration with 6-hydroxydopamine and due to terminal, rather than fiber of passage, uptake by control injection into the dorsal NA bundle. It is concluded that the locus coeruleus is not an homogenous nucleus with respect to the origin of the noradrenergic projections to sundry forebrain, spinal and cerebellar areas but is comprised of distinct subdivisions of noradrenergic neurons.

Amygdala↗
PubMed2026

Biophysical mechanisms underlying the generation and maintenance of rule-learning engram.

Training rodents in a particularly difficult olfactory-discrimination task results with acquisition of high-skill to perform the task superbly, termed 'rule-learning'. We show that rule-learning occurs abruptly, in a "light-bulb moment". Using whole-cell patch-clamp recordings from the piriform cortex (PC) of Fos2A-iCreER/TRAP2 mice, we target activated-neurons, expressing immediate early genes (IEG). We notice, from the onset of training, IEG-positive neurons from trained animals display enhanced intrinsic excitability. Subsequently, synaptic excitation and inhibition are enhanced in these neurons, in a coordinated, cell-wide process. Additionally, in parallel, we detect the density of IEG-expressing neurons sharply declines. Double labeling with TRAP and c-Fos reveal that nearly two-thirds of the rule-memory cell ensemble neurons are activated from the beginning of training. Silencing TRAP-expressing neurons using inhibitory DREADD leads to a complete loss of rule memory. Hence, we propose that rule learning occurs at a discrete moment and is developed through a gradual process that stabilizes the memory of the rule.

Animals↗
PubMed1979

5-HT concentration in cat's brain.

Endogenous concentrations of TRP, 5-HT and 5-HIAA were determined in the different cortical and subcortical areas of adult cat's brain, using ion-exchange chromatography and spectrofluorimetric methods. Tryptophan is homogeneously distributed in all structures of the brain. 5-HT is mainly accumulated in the brain stem, hypothalamus and caudate nucleus, but also in cortical areas as olfactory and piriform gyrus. The ratio 5-HIAA/5-HT shows that 5-HT utilization is higher in the structures containing small amounts of 5-HT. Using the radioenzymatic assay described by Saavedra et al. (1973), the rostrocaudal distribution of 5-HT content was determined in olfactory and piriform cortex. Important concentrations of 5-HT were detected in the prepiriformis and anterior amygdaloidea areas. Using the same assay and microdissection on frozen frontal slices of the brain, the distribution of 5-HT concentration throughout the different layers of cortical areas was studied. Piriform, olfactory and sigmoid cortex present high concentrations in the superficial layers, including the molecular one. These results were confirmed by uptake studies, made on crude homogenates from frozen tissue, suggesting that 5-HT is mainly contained in the most external cortical terminals.

Animals↗
PubMedDate not supplied

[Descending connections of the dorsal cortex in turtles].

Efferent connections of the dorsal cortex have been studied in the tortoises Emys orbicularis and Testudo horsfieldi using the degeneration tracing after dorso-medial lesions of this zone. Terminal degeneration was found in the hippocampal and piriform cortex, in the structures of striatum (d.v.r. bandle, putamen) and in the nucleus (centralis) lateralis and nucleus geniculatus lateralis of the thalamus. Fiber degeneration was also found in the fornix, hippocampal commissure, in the medial and lateral forebrain bundles including dorsal and ventral peduncies.

Animals↗
PubMed1978

Histochemical labeling of beta-adrenergic receptors in the mouse central nervous system by 9-amino-acridin propranolol.

A new fluorescent beta-adrenergic antagonist, 9-amino-acridin propranolol (9-AAP), was administered intravenously to living mice. In the cerebral cortex, the highest concentration of 9-AAP was noted in the hippocampal formation, where it distinctly labeled the hippocampal pyramidal cell layer and the granule cell layer of the dentate gryus. High uptake occurred in the pyramidal cell layer of the piriform cortex. In the neocortex, fluorescence was less dense and more diffuse but confined to the basal layers. A similar pattern was observed in the basal layers of the cingulate cortex, but an additional high-density dotted fluorescence labeled its layer II. In the cerebellar cortex, 9-AAP was localized within the Purkinje cell layer. In the spinal cord, the highest density of fluorescence was observed in the nuclear collections of alpha-motoneurons. The findings were similar to those observed in the central nervous system of the rat and support the reproducibility of the method. 9-AAP may be used in vivo as a fluorescent probe to map out the central beta-adrenergic receptor system.

Acridines↗
PubMed1978

Afferent connections of the entorhinal area in the rat as demonstrated by retrograde cell-labeling with horseradish peroxidase.

The entorhinal cortex (EC) of the rat has been divided into medial (MEA) and lateral (LEA) subdivisions. In order to analyze its afferent connections, small deposits of horseradish peroxidase (HRP) were placed at various loci within EC. The patterns of retrograde cell-labeling charted in 18 such cases suggested that EC is projected upon by several allocortical and subcortical structures and that there are differences in the afferent connections of the two subdivisions. Thus, although HRP injection of either division of EC led to cell-labeling in the hippocampal formation, most in ammonic field CA1 and the subiculum, several cells of the presubiculum were preferentially labeled by injection of MEA. Injections of LEA, but not those in MEA, resulted in substantial cell-labeling in the anterior piriform cortex of both hemispheres. Regardless of the location of its injection site within EC, the enzyme labeled cells in the diagonal band nucleus of Broca, amygdala and claustrum. The pattern of cell-labeling in the diagonal band nucleus extended into the ventrolaterally contiguous nucleus basalis after injection of LEA and into the dorsally contiguous medial septal nucleus after injection of MEA Whereas HRP deposits in either division of EC resulted in cell-labeling in the cortical and medial nuclei of the amygdala, only those deposits which involved LEA led to cell-labeling in the posterior part of the lateral nucleus. In the thalamus, labeled cells were found in the rostral part of the paratenial, periventricular and reuniens nuclei. Finally, at midbrain levels, numerous labeled cells appeared in the dorsal raphe nucleus, a few in the median raphe and locus coeruleus, and, only after rostral EC injection, in the ventral tegmental area.

Afferent Pathways↗
PubMed1978

The islands of Calleja: organization and connections.

The islands of Calleja (IC) in the rate are composed of seven small groups of granule cells in the polymorph layer of the olfactory tubercle and one large group, the insula magna, which lies along the border between septum, nucleus accumbens and nucleus of the diagonal band. The cytoarchitecture and neuronal morphology of the IC and surrounding cells, studied using Nissl-stained and Golgi-Kopsch material, are described. In addition, the afferent and efferent connections of the IC were analyzed using fluorescence histochemistry, the autoradiographic tracing method, and the anterograde and retrograde horseradish peroxidase methods. Topographically organized projections to the IC from the dopamine-containing cells of the substantia nigra-ventral tegmental area are demonstrated by the glyoxylic acid fluorescence histochemical method and the autoradiographic tracing technique. Anterograde and retrograde horseradish peroxidase studies provide evidence for reciprocal, topographically organized interconnections between the IC and the septum, nucleus accumbens, amygdala and piriform cortex. These observations indicate that the IC constitute a unique population of granule cells, located in the olfactory tubercle, innervated by dopamine neurons of the mesencephalon and interconnected with olfactory and non-olfactory components of the basal forebrain.

Animals↗
PubMed1979

Ibotenic acid-induced neuronal degeneration: a morphological and neurochemical study.

Possible neurotoxic actions of intracerebral injections of ibotenic acid, a conformationally restricted analogue of glutamic acid, have been evaluated in rat brain and compared with those of kainic acid. Light microscopical analysis revealed that ibotenic acid produced a marked disappearance of nerve cells in all areas studied, namely striatum, the hippocampal formation, substantia nigra and piriform cortex. Lesions in areas distant to the injection site were not seen. Axons of passage and nerve terminals of extrinsic origin did not seem to be damaged, since, e.g., no apparent degeneration of the dopaminergic terminals in the neostriatum was observed except for a small area surrounding the cannula. In the neostriatum, enkephalin immunoreactive neuronal cell bodies as well as nerve terminals disappeared after injection of ibotenic acid into this nucleus. After injection into the substantia nigra tyrosine hydroxylase immunoreactive cell bodies in the zona compacta disappeared, whereas no certain effect could be seen on the enkephalin immunoreactive nerve fibers. In vitro experiments, conducted with striatal synaptosomal and membrane preparations, showed that ibotenic acid differed from kainic acid by being devoid of a significant inhibitory effect on high affinity glutamate uptake and by having a low affinity for 3H-kainic acid binding sites. Furthermore, ibotenic acid did not interfere with the binding of a number of radioligands for other transmitter receptors. As compared to kainic acid, ibotenic acid has the advantage of being less toxic to the animals and of producing more discrete lesions, possibly due to faster metabolism and/or other fundamental biochemical differences. Because of these special features, ibotenic acid seems to represent a valuable new tool in the morphological and functional analysis of central neuronal systems.

Animals↗
PubMed1978

Direct mapping of beta-adrenergic receptors in the rat central nervous system by a novel fluorescent beta-blocker.

DL-N-(2-Hydroxy-3-napthyloxypropyl)-N'-dansylethylenediamine, dansyl analogue of propranolol (DAPN) is a novel fluorescent beta-adrenergic antagonist with high affinity to beta-receptors. The distribution pattern of DAPN fluorescence was studied in the rat central nervous system subsequent to its intravenous administration to living rats. DAPN distinctly labels specific regions and cells in the central nervous system (CNS). Highly dense DAPN fluorescence was observed in the pyramidal cell layer of the hippocampus, the granule cell layer of the dentate gyrus, the basal layers of the piriform cortex and the neocortex, the cerebellar Purkinje cell layer, and the spinal a-motoneurons. Pretreatment of control rats with DL-and L-propranolol markedly decreased the intensity and density of DAPN fluorescence in the tissue sections, whereas prior administration of D-propranolol had almost no effect. Pretreatment with large doses of reserpine did not alter the pattern of DAPN fluorescence. These findings were identical to those observed with another fluorescent beta-blocker, 9-aminoacridino-propranolol (9-AAP). Our data suggest that fluorescent beta-adrenergic antagonists may be used in vivo for the direct probing of the beta-receptors within the mammalian CNS.

Animals↗
PubMed1979

Functional development of dopamine receptors in the rat forebrain.

Dopamine (DA) was injected unilaterally into the dorsal caudate-putamen (D-CPU), ventral caudate-putamen (V-CPU), piriform cortex (PIR), olfactory tubercle (OTU) and frontal cortex (FC) of two day old rats and rotational behavior observed. Injection of DA into D-CPU, PIR, and OTU produced a contralateral postural deviation which differed significantly from the ipsilateral deviation produced by control injections. Only DA injections into PIR and OTU produced contralateral turning differing significantly from the effects of control injections. These results suggest that the DA receptors in C-CPU, PIR, and OTU involved in rotational behavior are functionally mature at two days of age and that the two components of rotation, postural deviation (direction) and turning (locomotion), involve different neural systems at this age. The developing rat is suggested as a valuable tool for understanding the neural circuitry and pharmacology of rotational behavior.

Animals↗
PubMed2026

Causal relationships between somatic movement, brain structures, and mental well-being: A multi-stage Mendelian randomization study.

BACKGROUND: While the relationships between somatic movement, mental well-being, and brain health have been well established, the causal nature and underlying mechanisms of such associations remain incompletely understood. METHODS: By applying multi-stage Mendelian randomization to multi-source summary data derived from genome-wide association studies, we examined the causal effects of 4 somatic movement measures on 2 mental well-being indices and 13 types of brain structures, followed by testing the mediating roles of brain structures in accounting for the causal associations between somatic movement and mental well-being. RESULTS: Two-sample Mendelian randomization revealed that more physical activity was causally associated with greater mental well-being (life satisfaction and positive affect), while more sedentary behavior (longer leisure screen time and more sedentary behavior at work) with lower mental well-being. With respect to brain structures, sedentary behavior was causally linked to decreased volume, surface area, and local gyrification index in distributed cortical regions. Remarkably, decreased surface area of the piriform cortex was found to mediate the causal associations between sedentary behavior and lower mental well-being. CONCLUSIONS: Our findings not only complement and extend earlier reports on the associations of somatic movement with mental well-being and brain health by further resolving the causality but also help elucidate the neural mechanisms by which sedentary behavior adversely affects mental well-being.

Humans↗
PubMed1978

[Features of the development of the dendrites of differentiating pyriform cerebellar cortex neurons in mammals and man].

Pecularities of development of the differentiating piriform neuron cerebellum cortex dendrite system in the mammals and in man were studied with light and electron microscopy. Three consequent stages are involved in the process: the formation of a dilated portion of apical (supranuclear) cytoplasm with an increased amount of organelles; the formation of a temporary apical cytoplasmic mitre (cone); the development of the dendrite system occurring on the background of reduction of this temporary cytoplasmic formation. In the course of differentiation, a distinct change of the dendrite cytoplasm contents from reticular to tubular ones takes place.

Animals↗