Biomedical subjects

F Reinoso-Suárez

Publications and source records attributed to F Reinoso-Suárez.

At least 19 recordsLinked to original sources

PubMed2006

GABAergic structures in the ventral part of the oral pontine reticular nucleus: An ultrastructural immunogold analysis.

GABA mediates inhibitory effects in neurons of the ventral part of the oral pontine reticular nucleus (vRPO). Evidence increasingly suggests that GABA plays an important role in the modulation of rapid eye movement (REM) sleep generation in the cat vRPO. Here, we investigate the anatomical substrate of this modulation using GABA immunocytochemistry. Immunoperoxidase labeling revealed a few small GABA-immunoreactive cell bodies scattered throughout the vRPO. The numerical densities of all vRPO synapses and the GABA-immunoreactive synapses were estimated, at the electron microscopical level, by using a combination of the physical disector and the post-embedding immunogold techniques. We estimated that 30% of all vRPO synaptic terminals were immunoreactive to GABA. Our findings support the hypothesis that vRPO neuron activity is significantly controlled by inhibitory GABAergic terminals that directly target somata and the different parts of the dendritic tree, including distal regions. GABAergic input could inhibit vRPO REM sleep-inducing neurons during other states of the sleep-wakefulness cycle such as wakefulness or non-REM sleep.

Animals↗

PubMed2002

Firing activity and postsynaptic properties of morphologically identified neurons of ventral oral pontine reticular nucleus.

The ventral part of the oral pontine reticular nucleus (vRPO) is an important region for the generation and maintenance of REM sleep. Firing activity and synaptic response properties of morphologically identified vRPO neurons have been investigated in urethane-anaesthetized cats. Extracellular recordings were performed through recording micropipettes and neurons were extracellularly stained with biocytin. Two types of neurons were identified under spontaneous conditions: type I neurons (77%) are characterized by non-rhythmic firing; type II neurons (23%) display single spikes firing rhythmically at between 7 and 22 Hz. Type I neurons displayed ellipsoid somata with thick dendritic trunks and axons that arose from either the soma or the initial dendritic segment; these axons could not be clearly followed. Type II neurons showed polygonal somata with radial dendrites; their axons branched at a small distance from the soma. Electrical stimulation of the contralateral vRPO elicited responses in both neuron types (57% and 31%, respectively); this effect was blocked by the non-NMDA glutamatergic receptor antagonist CNQX. Electrical stimulation of the PpT evoked orthodromic responses in type I neurons (41%) and inhibited the firing rate of all type II neurons for 50-100 ms. Both effects were blocked by the muscarinic receptor antagonist atropine. The cholinergic agonist, carbachol, increased the firing rate in most type I neurons and inhibited most type II neurons in these animals. The results demonstrated that the activity of vRPO neurons is modulated through the postsynaptic activation exerted by extrinsic afferents on cholinergic and glutamatergic receptors.

Acetylcholine↗

PubMed2000

Ultrastructural synaptic organization of axon terminals in the ventral part of the cat oral pontine reticular nucleus.

In an attempt to contribute to the current knowledge of the brainstem reticular formation synaptic organization, the ultrastructure and distribution of synaptic terminal profiles on neurons in the ventral part of the oral pontine reticular nucleus (vRPO), the rapid eye movement (REM) sleep-induction site, were studied quantitatively. Terminals with asymmetric contacts and rounded vesicles were classified according to vesicle density as type I or II (high or low density, respectively). The area, apposed perimeter length, and mitochondrial area of type I terminals, on average, were significantly smaller than those of type II terminals. Type III and IV terminals had symmetric contacts and oval and/or flattened vesicles; type III terminals formed synapses between them and on initial axons. Type V and VI terminals showed characteristics intermediate to those of asymmetric and symmetric synapses. Interestingly, some terminal features were related to both terminal area and postsynaptic dendritic diameter. The percentages of different synapses sampled on somata were as follows: asymmetric synapses (usually formed by type II terminals; mean +/- S.D.), 26.4% +/- 3%; symmetric synapses, 46.7% +/- 5.2%; and intermediate synapses, 26.9% +/- 6.1%. The percentages of different synapses sampled on dendrites were asymmetric synapses, 62.1% +/- 9%; symmetric synapses, 25.6% +/- 8.1%; and intermediate synapses, 12.3% +/- 1.7%. Comparison between large- and small-diameter dendrites revealed that the percentages of symmetric synapses and type II terminals decreased, whereas the percentages of type I terminals increased as postsynaptic dendritic diameters became smaller. Synaptic density was approximately four times lower on somata than on dendrites. The vRPO synaptic organization reflects some patterns that are similar to those found in other regions of the central nervous system as well as specific synaptic patterns that are probably related to its functions: the generation and maintenance of REM sleep and the control of eye movement or limb muscle tone.

Animals↗

PubMed2000

Serotonergic connections to the ventral oral pontine reticular nucleus: implication in paradoxical sleep modulation.

Cholinergic microstimulation of the ventral part of the oral pontine reticular nucleus (vRPO) in cats generates and maintains paradoxical sleep. The implication of rostral raphe nuclei in modulating the sleep-wakefulness cycle has been based on their serotonergic projections to the pontine structures responsible for the induction of paradoxical sleep. However, serotonergic neurons have also been described in brainstem structures other than the raphe nuclei. The aim of the present work is to trace the origin of the serotonergic afferents to the vRPO and to the locus coeruleus alpha and perilocus coeruleu alpha nuclei, closely related with different paradoxical sleep events. Anterograde and retrograde horseradish peroxidase conjugated with wheat germ agglutinin tracer injections in these nuclei in cats were combined with serotonin antiserum immunohistochemistry. Our results demonstrate that reciprocal connections linking the rostral raphe nuclei to those oral pontine nuclei are scarce. The percentage of double-labeled neurons after injections in the vRPO averaged 18% in rostral raphe nuclei, while a level of 82% was estimated in mesopontine tegmentum structures other than the raphe nuclei. These results showed that the main source of serotonin to the vRPO, implicated in generation and maintenance of paradoxical sleep, arises from these mesopontine tegmentum structures. This indicates that the serotonin modulation of paradoxical sleep could be the result of activation in non-raphe mesopontine tegmentum structures. The existence of a complicated network in the vRPO, which maintains a balance between different neurotransmitters responsible for the generation and alternance of paradoxical sleep episodes, is discussed.

Animals↗

PubMed2000

The anatomical connections of the macaque monkey orbitofrontal cortex. A review.

The orbitofrontal cortex (OfC) is a heterogeneous prefrontal sector selectively connected with a wide constellation of other prefrontal, limbic, sensory and premotor areas. Among the limbic cortical connections, the ones with the hippocampus and parahippocampal cortex are particularly salient. Sensory cortices connected with the OfC include areas involved in olfactory, gustatory, somatosensory, auditory and visual processing. Subcortical structures with prominent OfC connections include the amygdala, numerous thalamic nuclei, the striatum, hypothalamus, periaqueductal gray matter, and biochemically specific cell groups in the basal forebrain and brainstem. Architectonic and connectional evidence supports parcellation of the OfC. The rostrally placed isocortical sector is mainly connected with isocortical areas, including sensory areas of the auditory, somatic and visual modalities, whereas the caudal non-isocortical sector is principally connected with non-isocortical areas, and, in the sensory domain, with olfactory and gustatory areas. The connections of the isocortical and non-isocortical orbital sectors with the amygdala, thalamus, striatum, hypothalamus and periaqueductal gray matter are also specific. The medial sector of the OfC is selectively connected with the hippocampus, posterior parahippocampal cortex, posterior cingulate and retrosplenial areas, and area prostriata, while the lateral orbitofrontal sector is the most heavily connected with sensory areas of the gustatory, somatic and visual modalities, with premotor regions, and with the amygdala.

Animals↗

PubMed2000

Cortical connections of the insular and adjacent parieto-temporal fields in the cat.

We present a comprehensive analysis of the cortical connections of the insular and adjacent cortical areas in the domestic cat by using microinjections of wheat-germ agglutinin conjugated to horseradish peroxidase. We examined the identity and extent of the cortical fields connected to each area, the relative anatomical weights of the various connections, their laminar origin, and their paths across the cerebral commissures. Our main finding is that despite their relatively small size and close apposition, the connections of the insular and adjacent areas are far more widespread and more specific to each area than previously realized, suggesting that each area is involved in disparate aspects of cortical integration. The granular insular area is linked to a constellation of somatosensory, motor, premotor and prefrontal districts. The dysgranular insular area is chiefly associated with lateral prefrontal and premotor, lateral somatosensory and perirhinal cortices. The dorsal agranular insular area is connected with limbic neocortical fields, while the ventral agranular insular area is associated with an array of olfactory allocortical fields. The anterior sylvian area is associated with visual, auditory and multimodal areas, with the dorsolateral prefrontal cortex, and with perirhinal area 36. The parainsular area is linked to non-tonotopic auditory and ventromedial frontal areas. Trajectories followed by the callosal axons of each of the investigated areas are extremely divergent. As a whole, the picture of the insular region that emerges from this and a parallel study (Clascá et al., J Comp Neurol 384:456-482, 1997) is that of an extreme heterogeneity, both in terms of histological architecture and neural connections. Comparison with earlier published reports on primates suggests that most, but not all, of the areas we investigated in cats may have an direct counterpart within the insula of Old World monkeys.

Afferent Pathways↗

PubMed1998

Neurotransmitter actions on oral pontine tegmental neurons of the rat: an in vitro study.

The actions of neurotransmitters involved in the sleep-wakefulness cycle on neurons located in the ventral part of the oral pontine tegmentum were studied in a rat brain-slice preparation. Results show that glutamate and histamine evoke depolarizations and spike firing while serotonin and gamma-aminobutyric acid evoke hyperpolarizations. The excitatory and inhibitory actions of these neurotransmitters increase pontine neuron activity during the conditions occurring during paradoxical sleep.

Animals↗

PubMed1998

Sleep patterns after carbachol delivery in the ventral oral pontine tegmentum of the cat.

This study examines dose-related effects on sleep produced by low-volume and low-dose carbachol microinjections in the ventral part of the cat nucleus reticularis pontis oralis. Carbachol microinjections (0.04, 0.08, 0.8 or 4 microg; volume 20 nl) in this location triggered paradoxical sleep with a very short dose-unrelated latency. The four carbachol doses effectively generated all the polygraphic and behavioral signs of paradoxical sleep when microinjected at any level within the ventral part of the nucleus reticularis pontis oralis (AP 0.5 to -3.5, L 0.5-3.5, V 3.5-5.0, on the Reinoso-Suárez atlas [Topographischer Hirnatlas der Katze (1961); Merck, Darmstadt]). The dose-related increase of total paradoxical sleep time was due to the increase in both the duration and number of paradoxical sleep episodes. This paradoxical sleep increase was associated with a dose-related decrease in the amount of time spent in both slow wave sleep and drowsiness, but not with any decrease in total wakefulness. The lengthening of the latency to slow wave sleep onset was dose related. These results show that the ventral oral pontine tegmentum is a very sensitive site for the induction and maintenance of paradoxical sleep.

Animals↗

PubMed1997

Neocortical and hippocampal electrical activities are similar in spontaneous and cholinergic-induced REM sleep.

Neocortical and hippocampal EEG power spectra obtained during REM-like sleep induced by unilateral carbachol microinjections (0.01 M, 0.02 M and 0.2 M; volume 20 nl) into the ventral part of the nucleus reticularis pontis oralis have been compared with EEG power spectra obtained during spontaneous REM sleep. Our findings indicate that neocortical and hippocampal electrical activities during the REM-like state generated by carbachol delivery in this pontine region mimic those present in spontaneous REM sleep.

Acetylcholine↗

PubMed1997

Insular cortex and neighboring fields in the cat: a redefinition based on cortical microarchitecture and connections with the thalamus.

The insular areas of the cerebral cortex in carnivores remain vaguely defined and fragmentarily characterized. We have examined the cortical microarchitecture and thalamic connections of the insular region in cats, as a part of a broader study aimed to clarify their subdivisions, functional affiliations, and eventual similarities with other mammals. We report that cortical areas, which resemble the insular fields of other mammals, are located in the cat's orbital gyrus and anterior rhinal sulcus. Our data suggest four such areas: (a) a "ventral agranular insular area" in the lower bank of the anterior rhinal sulcus, architectonically transitional between iso- and allocortex and sparsely connected to the thalamus, mainly with midline nuclei; (b) a "dorsal agranular insular area" in the upper bank of the anterior rhinal sulcus, linked to the mediodorsal, ventromedial, parafascicular and midline nuclei; (c) a "dysgranular insular area" in the anteroventral half of the orbital gyrus, characterized by its connections with gustatory and viscerosensory portions of the ventroposterior complex and with the ventrolateral nucleus; and (d) a "granular insular area", dorsocaudal in the orbital gyrus, which is chiefly bound to spinothalamic-recipient thalamic nuclei such as the posterior medial and the ventroposterior inferior. Three further fields are situated caudally to the insular areas. The anterior sylvian gyrus and dorsal lip of the pseudosylvian sulcus, which we designate "anterior sylvian area", is connected to the ventromedial, suprageniculate, and lateralis medialis nuclei. The fundus and ventral bank of the pseudosylvian sulcus, or "parainsular area", is associated with caudal portions of the medial geniculate complex. The rostral part of the ventral bank of the anterior ectosylvian sulcus, referred to as "ventral anterior ectosylvian area", is heavily interconnected with the lateral posterior-pulvinar complex and the ventromedial nucleus. Present results reveal that these areas interact with a wide array of sensory, motor, and limbic thalamic nuclei. In addition, these data provide a consistent basis for comparisons with cortical fields in other mammals.

Animals↗

PubMed1997

Electrophysiological properties and cholinergic responses of rat ventral oral pontine reticular neurons in vitro.

In order to characterize the electrophysiological properties of morphologically identified neurons of the ventral part of the oral pontine reticular (vRPO) nucleus and the effects of cholinergic agonists on them, intracellular recordings were obtained from 45 cells in a rat brain-slice preparation. Intracellular staining was performed with 2% biocytin in potassium acetate (1 M)-filled micropipettes. Results demonstrated the presence of two types of vRPO neurons. Type I cells (n = 12, 24%) were characterized by a break with a decrease of the depolarizing slope following hyperpolarizing pulses which delayed the return to the resting Vm and subsequent spike-firing. The delay was antagonized by 4-AP (200-500 microM) which specifically blocks the transient outward K+-mediated current I(A). Type II neurons (n = 38, 76%) displayed a typical depolarizing sag during hyperpolarizing current pulses which was blocked by Cs+. This behavior is characteristic of the hyperpolarization-activated current I(Q). These two neuronal types displayed different morphological features. Most type I and II cells (100 and 73.7%, respectively) were depolarized by acetylcholine (1-15 microM), carbachol (0.5-1 microM) and muscarine (1-10 microM) through the activation of post-synaptic muscarinic receptors. The remaining type II cells (26.3%) were hyperpolarized (1-10 min, 3-15 mV) through the activation of post-synaptic muscarinic receptors. Results are consistent with the hypothesis that the vRPO could be a neuronal target of Cch in eliciting paradoxical sleep because most of its neurons are activated by muscarinic agonists.

4-Aminopyridine↗

PubMed1995

Projections from the 17/18 visual area transition zone to the ipsilateral visual field representation in the cat superior colliculus.

We demonstrate by retrograde tracing methods that the transition zone between visual cortical areas 17 and 18--where a representation of the ipsilateral visual field (IVF) has been described--projects to the IVF representation in the ipsilateral superior colliculus. The stratum griseum superficiale is the target of this retinotopically organized cortical projection to the rostral part of the superior colliculus.

Animals↗

PubMed1995

Afferent connections of the lateralis medialis thalamic nucleus in the cat.

We have used anterograde and retrograde horseradish peroxidase tracing methods in this study. Peroxidase injections in the lateralis medialis thalamic nucleus (LM) of the cat resulted in labeled neurons in cortical and subcortical structures that averaged 71% and 29%, respectively. Every LM sector receives abundant projections from the polymodal sylvian anterior cortical area, the reticular thalamic nucleus, and the stratum opticum and intermediate layer of the superior colliculus. Less abundant but consistent projections were detected in cingular, auditory II, lateral suprasylvian and anterior ectosylvian visual cortices, and cortical area 7. A topographical distribution of afferent connections to different LM sectors arising from other cortical and subcortical structures could be established. The ventromedial sector receives connections mainly from the insular agranular, limic and prefrontal cortical areas, as well as from brain stem structures and the contralateral pretectal region. The dorsolateral sector is mainly related to cortical areas and subcortical structures processing visual information. The existence of overlap among neuronal LM populations receiving and sending connections to and from various cortical areas suggests that this nucleus is an appropriate substrate for effective interaction between different and distant cortical areas.

Afferent Pathways↗

PubMed1995

Acetylcholinesterase histochemistry in the macaque thalamus reveals territories selectively connected to frontal, parietal and temporal association cortices.

The patterns of histochemical staining for acetylcholinesterase (AChE) activity in the macaque thalamus were analyzed and compared with the distribution of cells and terminals labeled from injections of axonal tracers in the dorsolateral and orbital prefrontal cortex, in area 7a of the posterior parietal cortex and in the polysensory cortex of the superior temporal sulcus. AChE histochemistry is very useful in delineating the thalamic nuclei connected with the association cortex and in uncovering thalamic subdivisions that are barely evident on cytoarchitectonic grounds. Moreover, AChE activity reveals previously unrecognized heterogeneities within several thalamic nuclei, like the ventral anterior (VA), where a new ventromedial subdivision (VAvm) is described, the medial pulvinar (PulM) or the mediodorsal nucleus (MD). In this nucleus three distinct chemical domains are present: the medial, ventral and lateral sectors characterized by low, moderate and high AChE activities, respectively. The staining pattern of the lateral sector is markedly heterogeneous with patches of intense AChE activity surrounded by a moderately stained matrix. The MD medial sector is connected with the orbitofrontal cortex, whereas the AChE-rich patches in the lateral sector are selectively connected with the dorsolateral prefrontal, parietal and temporal association cortices. In the PulM, a dorsomedial AChE-rich patch is selectively connected with the orbitofrontal cortex, whereas the surrounding territory, which shows moderate AChE activity, is preferentially connected with the parietal and temporal cortices. Chemically specific domains in the anterior, ventral anterior, midline, and intralaminar thalamic nuclei are also connected with the examined association cortices. These findings indicate that the topographic patterns of the thalamo-cortical connections of primate association areas conform to the chemical architecture of the thalamus. This implies that because each cortical area is connected to a particular set of thalamic regions, the influence of the thalamus on cortical function is exclusive for each area, highly diverse among the various association areas, and subject to a wide range of modulation at the thalamic level.

Acetylcholinesterase↗

PubMed1994

The lateral geniculate nucleus projects to the inferior temporal cortex in the macaque monkey.

The dorsal lateral geniculate nucleus of the thalamus (dLGN) projects to several extrastriate areas of the macaque brain. The extent of the dLGN projection to the visual temporal cortex was investigated using retrogradely transported dyes. A population of dLGN neurones was labelled after injections in the inferior temporal cortex (ITC) including the lower bank of the superior temporal sulcus and the inferior temporal convexity. The labelled neurons were located in the lateral half of the posterior one-third of the dLGN and predominated in the interlaminar zones or close to the borders of the parvocellular layers. This direct projection from the dLGN to the ITC may mediate some of the visual abilities known to be retained by destriated animals.

Amidines↗

PubMed1994

Location and anatomical connections of a paradoxical sleep induction site in the cat ventral pontine tegmentum.

The brainstem mechanisms for the generation of paradoxical sleep are under considerable debate. Previous experiments in cats have demonstrated that injections of the cholinergic agonist carbachol into the oral pontine tegmentum elicit paradoxical sleep behaviour and its polygraphic correlates. The different results on the pontine structures that mediate this effect do not agree. We report here that limited microinjections of a carbachol solution into the ventral part of the oral pontine reticular nucleus in the cat induce, with a short latency, a dramatic, long-lasting increase in paradoxical sleep. Moreover, neuronal tracing experiments show that this pontine site is connected with brain structures responsible for the different bioelectric events of paradoxical sleep. These two facts suggest that the ventral part of the oral pontine reticular nucleus is a nodal link in the neuronal network underlying paradoxical sleep mechanisms.

Animals↗

PubMed1993

Nicotinamide-adenine dinucleotide phosphate diaphorase activity matches acetylcholinesterase-rich patches in the medial thalamic nuclei of the cat.

Patches of high nicotinamide-adenine dinucleotide phosphate diaphorase (NADPH-d) activity were found in the mediodorsal and midline thalamic nuclei of cats. These patches matched acetylcholinesterase (AChE)-rich patches within the medial thalamus, whereas other AChE-rich patches were NADPH-d negative. There were also patches of NADPH-d activity in the lateral habenula, but these did not match the AChE staining. These results suggest that the functional role of discrete thalamic regions may require the joint presence of AChE and NADPH-d enzymatic activities.

Acetylcholinesterase↗

PubMed1993

Rapid evolution of the visual system: a cellular assay of the retina and dorsal lateral geniculate nucleus of the Spanish wildcat and the domestic cat.

The large Spanish wildcat, Felis silvestris tartessia, has retained features of the Pleistocene ancestor of the modern domestic cat, F. catus. To gauge the direction and magnitude of short-term evolutionary change in this lineage, we have compared the retina, the optic nerve, and the dorsal lateral geniculate nucleus (LGN) of Spanish wildcats and their domestic relatives. Retinas of the two species have the same area. However, densities of cone photoreceptors are higher in wildcat--over 100% higher in the area centralis--whereas rod densities are as high, or higher, in the domestic lineage. Densities of retinal ganglion cells are typically 20-100% higher across the wildcat retina, and the total ganglion cell population is nearly 70% higher than in the domestic cat. These differences are confined to the populations of beta and gamma retinal ganglion cells. In contrast, the population of alpha cells is almost precisely the same in both species. The wildcat LGN is much larger than that of the domestic cat and contains approximately 50% more neurons. However, cell size does not differ appreciably in either the retina or LGN of these species. The differences in total numbers of ganglion cells and LGN neurons correspond neatly to the overall decline in brain size in the domestic lineage and to allometric predictions based on average species differences in body size. We suggest that an increase in the severity of naturally occurring cell death is the most plausible mechanism that can account for the rapid evolutionary reduction in cell populations in this feline lineage.

Animals↗