PubMed Health⌕ Search

Biomedical subjects

A R Cinelli

Publications and source records attributed to A R Cinelli.

11 recordsLinked to original sources
PubMed1992

Intracellular injection of vital dyes into single cells in the salamander olfactory epithelium.

Intracellular vital dye injection was used to examine the morphology of single sustentacular and receptor cells and the developmental fate of individual basal cells in the olfactory epithelium of the tiger salamander. In acute experiments, Lucifer yellow injections were used to identify single basal, receptor or sustentacular cells on the basis of their overall morphology. Dye-coupling between a number of the different epithelial cells was observed. Progeny of basal cells were examined by following labeled cells for up to 2 weeks using intracellular injection of rhodamine-labeled dextran. These experiments indicate that some olfactory epithelial cells are dye-coupled and that dye-filled basal cells can undergo division and migration.

Ambystoma↗
PubMed1992

Dendritic origin of late events in optical recordings from salamander olfactory bulb.

1. Optical recordings of membrane-potential changes were used to characterize the origin and properties of the electrical signals from the dendritic level in slices of the salamander olfactory bulb. 2. The optical events were correlated with field-potential waves recorded simultaneously. Both responses exhibited patterns similar to those found in other species. 3. Orthodromic stimulation evoked a compound action potential in the olfactory nerve fibers, followed by two additional principal waves (N1 and N2). These field-potential waves reflected excitatory postsynaptic potentials at the primary mitral/tufted and granule cell dendrites, respectively. 4. Extrinsic optical signals from horizontal slices stained with the pyrazo-oxonal dye RH-155 showed a characteristic sequence of depolarizing and hyperpolarizing events. All of the signals exhibited a wavelength dependence expected for this dye and were abolished in the presence of high K+ in the bath. 5. According to their time courses, depolarizing responses under normal recording conditions were divided into two components, fast and slow. Orthodromic stimuli evoked a fast presynaptic response that represents synchronous compound action potentials from olfactory nerve fibers. At subglomerular levels, additional fast responses could often be recorded at the peri/subglomerular level and in the mitral/tufted somata region. These postsynaptic responses partially coincided with the rising phase of a different depolarizing signal, a slow component characterized by its prolonged time course. 6. With orthodromic stimulation, this slow signal attained its largest amplitude in the zone between the glomeruli and the superficial part of the external plexiform layer (EPL). Antidromic stimuli evoked a signal with some similarities to the one evoked orthodromically, but originating in deeper EPL regions. 7. Slow components were characterized by their Ca dependence. Low Ca2+ medium, or calcium channel blockers, suppressed this optical component, whether evoked orthodromically, antidromically, or by direct stimulation. In addition, Ba2+ (2.5-3.6 mM) in the bath did not abolish these responses, suggesting that they do not reflect a glial depolarization in response to elevated extracellular K+ concentration ([K+]o). 8. Locally applied stimuli next to the glomerular layer elicited these signals in 5-10 microM tetrodotoxin (TTX) or in low extracellular Na+ concentration ([Na+]o) medium, but antidromic or orthodromic stimuli failed to evoke the response under these conditions. The sizes of the responses to local stimuli remained constant, but an increase in their duration was observed in either TTX or low [Na+]o. 9. gamma-Aminobutyric acid (GABA) and baclofen reduced the size of the slow components in a dose-dependent manner.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1990

Multiple site optical recording of transmembrane voltage (MSORTV), single-unit recordings, and evoked field potentials from the olfactory bulb of skate (Raja erinacea).

1. Multiple site optical recording of transmembrane voltage (MSORTV), together with conventional extracellular electrophysiological techniques were utilized with in vivo and in vitro preparations of the olfactory bulb of the Atlantic skate Raja erinacea to analyze electrical activity simultaneously in layers deep to the glomerular layer. 2. In the living animals and the in vitro isolated olfactory bulb, orthodromic stimulation evoked a compound action potential in the olfactory nerve fibers, followed by a series of early field-potential waves (N1, P1, N2, P2, N3, and N4). During paired stimulation experiments, unusual patterns of facilitation and suppression were observed for the N2 wave. 3. After orthodromic stimulation, single units, presumably mitral/tufted cells, exhibited a period of early discharge, followed by a period of suppression of spontaneous activity and of their test response in a pair stimulation paradigm. Some neurons also exhibited a labile period of reexcitation that was accompanied by a late surface negative field potential; these responses were also present in olfactory bulb slices. 4. Extrinsic absorption changes obtained from 500-microns saggital slices of the olfactory bulb, stained with the pyrazooxonal dye RH-155, consisted mainly of two types of depolarizing responses, a fast and a slow component, followed under some conditions by a late hyperpolarization. All signals exhibited wavelength dependences typical of the action spectrum of RH-155 and were abolished in the presence of tetrodotoxin (TTX) or high K+ in the bath. 5. The fast component of the optical signal represents synchronous compound action potentials conducted by the olfactory nerve fibers or evoked in the mitral/tufted somata and axonal pathways. The slow depolarizing optical signal appeared, after orthodromic stimuli, mainly in the zone between the glomeruli and the mitral/tufted layer; barium (1-10 mM), which depolarizes glial cells, increased its size and duration, suggesting that this signal does not reflect a glial response to [K+]o. 6. Different condition/test (C/T) intervals produced partial or complete suppression of the test response, depending on the recording site and the stimulus intensity. Just threshold orthodromic stimuli evoked an intermediate period of facilitation of the slow signals. A similar period was also observed in the N2 wave of the field potential. 7. Calcium channel blockers such as cadmium ion, or a low Ca2+ medium, suppressed the slow optical component whether evoked by orthodromic, antidromic, or direct stimulation. gamma-Aminobutyric acid (GABA) and baclofen also reduced or blocked the slow component of the extrinsic absorption signal.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Current generators and properties of late components evoked in rat olfactory cortex.

Following main olfactory bulb (MOB) stimulation at frequencies of 0.1-0.3 Hz, in addition to early field potentials, a frequency-sensitive, surface negative late N2 wave (latency range: 63-96 msec) followed occasionally by a late N3 transient, was evoked in the piriform cortex and endopiriform nucleus of the rat. The N2 wave inverted polarity at the Ib-II cortical layer interface (P2 wave) and was associated with late unit discharges 200 to 1200 microns deep to the turnover point. Response probability, peak latency, recovery curve and frequency-sensitivity of the P2 wave were not significantly different in animals under urethane or pentobarbital. Current-source-density (CSD) analysis revealed that the N2 wave generators were localized to the Ib-II layer interface. Since inhibitory activity does not contribute substantially to the second derivative curve, CSD analysis strengthens the assumption that late components (LCs) are excitatory events (compound EPSPs) presumably generated on the proximal apical dendritic segments of pyramidal cells by association axons. The early "b" wave in a test response was facilitated, rather than occluded, when a LC was present in the conditioning response, or when the priming volley was delivered to the mediodorsal thalamic nucleus. Clustering of unit and field activity in two distinct periods of the evoked response separated by a prolonged interval of cell silence suggests that cortical coding of olfactory cues might be more efficiently achieved by temporal modulation of the neuronal response rather than by spatial distribution of firing patterns.

Animals↗
PubMed1988

A computer program for automatic plotting of isopotential contours in CNS.

A computer program was developed in a Basic (Applesoft) version for generating up to five isopotential curves from field potentials recorded in nervous structures. Voltages are fed according to a cartesian coordinate system, and an area is delineated each four points in which a certain number of intermediate voltage points are calculated, according to the required resolution. The calculated values are compared to those prefixed for each curve and, if similar, their coordinates are stored in corresponding bidimensional matrixes. A special subroutine was designed for constructing an isometric tridimensional perspective of the isopotential curve ensemble. The reliability of this program was tested in the localization of sensory representation areas on the neocortex of the South American armadillo (Chaetophractus vellerosus) studied by evoked potential mapping following visual, auditory and somatosensory stimuli. The isopotential curves traced permitted a quantitative evaluation of the cortical activated areas, and from their topographical distribution, relative unresponsive zones could be inferred where only inconspicuous responses were obtained. It is concluded that the present program provides a reliable and fast method for studying the evoked potential's spatial distribution over the entire neocortex. In addition, it can be extended to the study of curves or contours which connect equivalent values pertaining to biophysical magnitudes other than voltage data.

Animals↗
PubMed1987

Reciprocal functional connections of the olfactory bulbs and other olfactory related areas with the prefrontal cortex.

Reciprocal putative connections of the prefrontal cortex (PFC) (agranular insular, ventral and lateral orbital region) with the ipsi and contralateral main olfactory bulb (IOB; COB), the mediodorsal thalamic nucleus (MD), the basolateral amygdaloid nucleus (BLA) and the piriform cortex (PC) were investigated with electrophysiological techniques. Evoked field responses and orthodromic unit driving, generated in PFC following electrical stimulation of the above mentioned structures, were abolished following topical application of KCl, except for COB evoked mass potentials. Thus, locally generated activity was elicited in agranular insular cortex following IOB activation, the same region where recently, the taste cortex in the rat was localized. Since gustatory-visceral afferent information reaches insular cortex via 2-3 synaptic relays, autonomic, olfactory and gustatory inputs may interact at this level, and, as suggested previously for the mouse, play a key integrative role in flavor perception. Antidromically invaded neurons, 47% of which were identified by the collision-extinction technique, were also found in PFC areas which overlapped to a considerable extent with those from which orthodromic unit responses were obtained. In particular, closely spaced neurons in ventrolateral orbital (VLO) and lateral orbital (LO) regions were antidromically invaded following IOB and PC shocks; some neurons antidromically discharged by IOB were also transsynaptically activated following PC stimulation. These findings are in agreement with recent neuroanatomical studies which demonstrate axonal projections from PFC neurons to the IOB and COB in the rat and South American armadillo. In addition, stimulation of PFC regions dorsal to the rhinal fissure mostly inhibited spontaneous unit discharges recorded at the mitral cell layer of the IOB, suggesting that this effect may be partially mediated by excitatory inputs of prefrontal axons onto granule cells. The conduction properties, antidromic thresholds and activity-dependent variations in conduction velocity (CV) of bulbopetal neurons in prefrontal cortex were found to be similar to those exhibited by cells projecting to the IOB from olfactory peduncle regions, but not to those present in bulbopetal neurons of the horizontal limb of diagonal band, indicating that the OB may be subjected to centrifugal control by at least two cell groups differing in both histochemical and electrophysiological properties.

Afferent Pathways↗
PubMed1986

Axonal projections and conduction properties of olfactory peduncle neurons in the armadillo (Chaetophractus vellerosus).

Extracellular unit recording was employed to study the axonal properties and efferent projections of antidromically identified neurons in the olfactory peduncle (OP) region of a primitive eutherian macrosmatic mammal, the south american armadillo (Chaetophractus vellerosus). Of 72 cells which satisfied the criteria for antidromic invasion, 55 (76%) and 17 (24%) responded to ipsi- and contralateral olfactory bulb (IOB; COB) stimulation, respectively. The absolute refractory period (3.25 +/- 0.3 ms; mean +/- SE) and the conduction velocity (CV; 1.94 +/- 0.2 m/s; mean +/- SE) of IOB and COB driven neurons were negatively correlated (r = -0.52; p less than 0.001). In paired-shock tests (8-1950 ms interval), and early supernormal period (SPN) of increased CV and excitability was found following the relative refractory period in 82% of tested cells (N = 50); this period was followed by a late subnormal phase (SBN) of decreased CV and increased threshold in 58% of neurons (N = 50). Significant correlations were found to exist between: CV and absolute magnitude of latency variation (r = -0.55; p less than 0.001; n = 43), CV and duration of SPN and SBN periods (r = -0.60; p less than 0.002; n = 24 and r = 0.58; p less than 0.02; n = 19, respectively) and between duration of SPN and SBN phases (r = 0.79; p less than 0.001; n = 30). Maximum latency variation during the SPN and SBN periods was attained in a gradual, additive manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

An automatic device for determining threshold variations in antidromically activated neurons.

A device was designed and constructed with the purpose of evaluating threshold variations for antidromic invasion of extracellularly recorded neurons. Identification of a neuron is carried out by two procedures, an amplitude discriminator, which isolates the spike from the baseline noise, and by a latency window which is set accordingly to the neuron's antidromic latency. During threshold evaluation, the duration of an electric pulse applied to the neuron's axon is automatically varied depending on the presence or not of an action potential. For a given spike, the stimulus is progressively decreased (-delta i) up to a point where the neuron ceases to respond and thereafter, the stimulus amplitude is progressively increased (+delta i) until slightly suprathreshold values are obtained. The procedure guarantees a discharge probability of the neuron equivalent to 50% of all applied stimuli, and the simple monitoring of the stimulus amplitude is enough to obtain the threshold value for a predetermined intensity. The reliability of this device was checked in studies related to threshold variations in neurons antidromically driven in prefrontal cortex following stimulation of the ipsi and contralateral olfactory bulb. Variations in excitability were found during and following tetanic stimulation and throughout the axon's supernormal conduction period. This technique allows the assessment of threshold variations in antidromic driving, not only in the present experimental design, but also in other conditions induced by changes in extracellular ionic concentrations, drug applications or in those produced by excitatory or inhibitory synaptic activity on the neuron under study.

Animals↗
PubMed1985

Variations in axonal conduction velocity in olfactory peduncle neurons of the armadillo.

Following electrical stimulation of the ipsi- or contralateral olfactory bulb, antidromically invaded neurons in the olfactory peduncle (OP) of the armadillo (a primitive mammal with a low brain temperature) show progressive decreases in conduction velocity when challenged with stimulation frequencies of 1-40 Hz. Antidromic latency also decreased or increased in a gradual, additive manner during the super- and subnormal period following twin pulses at intervals of 8-2000 ms. Since centrifugal OP axons excite inhibitory granular cells in the olfactory bulb, these effects may bear on the problem of the control of mitral cell excitability by central structures.

Animals↗
PubMed1985

Current generators and properties of early components evoked in rat olfactory cortex.

Depth-profile, current-source-density (CSD) and impedance analysis were used to determine the current generators of secondary waves "a" and "b" in the response evoked in pyriform cortex (PC) of the urethane anesthetized rat following OB or LOT stimulation. Positive peaks (sinks) in the second-derivative curves of the "a" and "b" waves were localized at 50-75 and 225-250 microns deep, respectively. Cortical impedance was significantly (p less than 0.01) correlated with the cell packing density of PC layers, being maximal close to the zero dipole point of the gross evoked response; magnitude of conductivity gradients was, however, insufficient to alter the interpretation of positive and negative peaks in terms of net membrane currents. Post-tetanic and/or frequency potentiation of PC responses but not long-term potentiation were found in the majority of animals tested. Recovery of the test "b" wave was faster when using paired-shock stimulation at 3.0 Hz than at 0.3 Hz; suppression of this component following a conditioning OB volley could be overcome and the "b" wave facilitated if either a long-latency component (i.e., 65-100 msec) was present in the priming response, or if the conditioning stimulus was delivered to the mediodorsal thalamic nucleus (MDT). These results confirm and extend similar ones in other species, suggesting that following OB or LOT stimulation three successive excitatory processes take place in PC neural elements of the rat under urethane anesthesia: an initial monosynaptic excitation of distal segments of apical dendrites of layer II cells, and to a lesser extent, also of layer III neurons ("a" wave), followed by action potentials in their respective somas (PS wave); subsequently, long association axons give rise to a di or polysynaptic compound EPSP in proximal apical and possibly also, in basal pyramidal dendrites ("b" wave; early reactivation process). Finally, a "late" reactivation takes place in PC involving neurons which participated in the early reactivation process (late component). In addition, heterosynaptic facilitation of the "b" wave in the PC evoked response follows MDT conditioning stimulation.

Animals↗