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T J Ruigrok

Publications and source records attributed to T J Ruigrok.

At least 55 records · Page 3Linked to original sources
PubMed1995

Olivary projecting neurons in the nucleus prepositus hypoglossi, group y and ventral dentate nucleus do not project to the oculomotor complex in the rabbit and the rat.

The nucleus prepositus hypoglossi, dorsal group y, ventral dentate nucleus, and medial vestibular nucleus all project to both the oculomotor complex and inferior olive. In the present study, we demonstrate with the use of retrograde double labeling techniques in rabbits and rats, that the neurons in these pre-oculomotor nuclei that project to the inferior olive are intermingled with those that project to the oculomotor nucleus, but that virtually none project to both.

Animals↗
PubMed1995

Cerebellar influence on olivary excitability in the cat.

This study examines the influence of the cerebellum on the excitability of inferior olivary neurons in the cat. Two major pathways from the cerebellar nuclei to the inferior olive have been investigated by electrophysiological and anatomical techniques. The first, excitatory pathway connects the cerebellar nuclei through nuclei at the mesodiencephalic junction with the inferior olive. The second is the direct, GABAergic, nucleo-olivary pathway. Intra- as well as extracellular recordings obtained in the rostral part of the medial accessory and principal olives revealed that electrical stimulation with a short burst of three pulses delivered at the mesodiencephalic junction results in short-latency activation (4-8 ms) of most olivary neurons. More than half of the units showed, in addition to the short-latency activation, a consistent response with a much longer latency (approximately 180 ms). Many units (66%) that responded to mesodiencephalic stimulation could also be activated by superior cerebellar peduncle stimulation with a similar stimulation paradigm (latency 9-15 ms). However, in such cases consistent long-latency responses were only rarely recorded (7%). To distinguish between the effect of the two pathways, both of which are activated by superior cerebellar peduncle stimulation, an electrolytic lesion of the nucleo-olivary fibres was made in the brainstem in six experiments. The effect of this lesion was verified in three cases by retrograde horseradish peroxidase tracing from the rostral inferior olive at the end of the experiment. This time only extracellular recordings were made. Stimulation of the mesodiencephalic junction still resulted in easily activated olivary units which showed an increased probability of firing a long-latency action potential. Stimulation of the superior cerebellar peduncle now resulted in a 50% decrease in probability of activating olivary units in the short-latency range. However, a five-fold increase in the chance of triggering action potentials in the long-latency interval was noted, implying that many units reacted only with a long-latency action potential. The results obtained with our experimental paradigm appear enigmatic since it is well established that the nucleo-olivary pathway is GABAergic and thus, by convention, should be inhibitory to the olivary neurons. However, it is possible to explain these results in terms of dynamic coupling of olivary neurons. This concept ascribes an important role to the nucleo-olivary pathway in regulating the degree of electrotonic coupling between olivary neurons (probably by a shunting mechanism) and as such may be an important instrument in the regulation of synchronous and rhythmic olivary discharges.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1995

Cerebellar projections to the red nucleus and inferior olive originate from separate populations of neurons in the rat: a non-fluorescent double labeling study.

In the rat, the extent of collateralization of projections from the cerebellar nuclei to the red nucleus and inferior olive was investigated using a retrograde double labeling technique. The combination of tracers selected, cholera toxin-beta-subunit and WGA-BSA-gold, not only enabled the use of small injection sites but also resulted in clearly distinguishable and permanently stained neurons that could be analyzed in counterstained sections.

Animals↗
PubMed1995

Lidocaine does not prevent the calcium paradox in rat hearts: a laser microprobe mass analysis (LAMMA) study.

The calcium paradox stands for the cell damage that occurs when isolated hearts are perfused with a Ca(2+)-free solution followed by perfusion with a Ca(2+)-containing solution. Although it is generally accepted that a massive Ca2+ influx during the Ca(2+)-repletion phase is responsible for the cell damage, there is no consensus about what makes the heart susceptible to the calcium paradox during the Ca(2+)-depletion phase. It has been suggested that the extent of the calcium paradox is primarily determined by accumulation of Na+ during Ca2+ depletion and a subsequent accumulation of Ca2+ via reverse Na(+)-Ca2+ exchange during Ca2+ repletion. According to another theory, weakening of intercalated disc junctions during Ca2+ depletion and contracture-mediated disruption of the cell membrane during Ca2+ repletion are responsible for the calcium paradox. In the present study we further investigated the possible role of Na+ in the development of the calcium paradox. During Ca2+ depletion, lidocaine was used to inhibit Na+ entry through the Na+ channels. Isolated rat hearts were perfused with Krebs Henseleit buffer (KH) containing 1.4 mM Ca2+ for 15 min, followed by 10 min of Ca(2+)-free perfusion and 10 min of reperfusion with Ca2+. In the treated group 0.1 mM lidocaine was present throughout the experiment. At the end of each experiment, Ca2+ cytochemistry was performed and the intracellular Ca2+ content was analyzed by laser microprobe mass analysis (LAMMA). The results show that during Ca2+ depletion, the intracellular Ca2+ content did not change significantly. Ca2+ repletion, however, gave rise to a full calcium paradox irrespective of the presence of lidocaine: massive cell damage and Ca2+ accumulation in the mitochondria. The results provide further evidence that intracellular Na+ accumulation during Ca2+ depletion is not involved in the occurrence of the calcium paradox.

Animals↗
PubMed1994

Olivary projecting neurons in the nucleus of Darkschewitsch in the cat receive excitatory monosynaptic input from the cerebellar nuclei.

The direct projection from the cerebellar nuclei to the inferior olive is GABAergic. In the present study, we investigated the projection from the cerebellar nuclei to the mesodiencephalic junction which is known to provide an excitatory projection to the inferior olive. The mesodiencephalic junction was studied in cat following anterograde transport of wheatgerm agglutinated horseradish peroxidase from the cerebellar nuclei in combination with: (1) retrograde transport of gold-lectin conjugate from the inferior olive; and (2) postembedding GABA-immunocytochemistry. Light microscopic analysis revealed that overlap of the anterograde and retrograde labeling was especially prominent in the nucleus of Darkschewitsch. Electron microscopic examination of this area showed: (1) that many cerebellar terminals made synaptic contacts with neurons that project to the inferior olive; (2) that virtually all cerebellar terminals were non-GABAergic and displayed an excitatory morphology; and (3) olivary projecting neurons were non-GABAergic. It is concluded that the indirect cerebellar projection to the inferior olive via the nucleus of Darkschewitsch is disynaptic and excitatory.

Animals↗
PubMed1993

Electron microscopy of in vivo recorded and intracellularly injected inferior olivary neurons and their GABAergic innervation in the cat.

This paper reports on the detailed morphology of inferior olivary neurons in the cat following electrophysiological examination, intracellular injection with horseradish peroxidase, and gamma aminobutyric acid (GABA) immunocytochemistry. The activity of olivary cells was recorded intracellularly in vivo and their response to mesodiencephalic stimulation was tested. In a number of cases their response to stimulation of the contralateral superior cerebellar peduncle was also tested. Mesodiencephalic stimulation resulted in monosynaptic, and superior peduncle stimulation in disynaptic activation of cells in the medial accessory and principal olivary subdivisions. Rebound olivary activity was usually only found after mesodiencephalic stimulation. Light microscopic investigation of osmicated and Araldite embedded Vibratome sections was facilitated considerably when performing the osmication in a glucose solution. Peroxidase labeled olivary cells, like that earlier described for Golgi-impregnated material, possess a complex globular dendritic geometry. Especially, and unlike Golgi material, the abundance of exceptionally long and complex spiny appendages could be appreciated. The axons usually stemmed from first order dendrites and did not give rise to recurrent axon collaterals. The ultrastructural analysis of this material, mainly from serial sections, was combined with postembedding GABA immunohistochemistry. In this way, GABAergic as well as non-GABAergic profiles were studied in conjunction with HRP labeled cellular elements. The GABAergic terminals usually contained pleomorphic vesicles and made symmetrical synapses whereas non-GABAergic terminals nearly always formed asymmetrical synapses and contained round or oval vesicles. Most, if not all, HRP labeled spiny appendages were incorporated in glomeruli. A particular spiny appendage may contribute more than one spine head to a glomerular core, which, on average, consisted of spiny elements of six different neurons. A glomerular core is surrounded by approximately the same amounts of GABAergic and non-GABAergic boutons. Also, all spiny appendages, and most of their individual spine heads, are contacted by GABAergic as well as non-GABAergic boutons. Spiny appendages on the axon hillock may be incorporated in dendritic glomeruli, however, most synapses with the hillock were made by GABAergic boutons. The combined physiological and morphological observations imply that 1) the cerebellar nuclei can exert an excitatory influence on inferior olivary neurons through a mesodiencephalic relay, 2) the GABAergic nucleo-olivary input seems to be capable of diminishing the oscillatory tendencies of olivary neurons, and 3) the mesodiencephalic (non-GABAergic) and cerebellar (GABAergic) input may subserve a timing function since these inputs systematically impinge upon the same olivary spines.

Animals↗
PubMed1993

Post-ischemic contractile dysfunction does not correlate with an elevated intracellular free [Mg2+]: a 31P-NMR study on isolated rat and rabbit hearts.

The aim of this study was to investigate whether intracellular free Mg2+ (Mgr), which increases during myocardial ischemia due to hydrolysis of ATP, remained elevated during reperfusion after a relatively short period of ischemia and thereby could account for temporary post-ischemic contractile dysfunction, often referred to as stunning. 31P-magnetic resonance (31P-NMR) spectroscopy was used to follow creatine phosphate, adenosine triphosphate, intracellular inorganic phosphate, intracellular pH and Mgr simultaneously with left ventricular developed pressure (LVDP) and coronary flow in isolated rat and rabbit hearts, which were perfused (37 degrees C) according to Langndorff. LVDP was measured in an isovolumic way by means of an intraventricular latex balloon. Rat hearts (300 beats/min) were made globally ischemic for 15 min and rabbit hearts (180 beats/min) for 15 or 20 min. All hearts were reperfused for 60 min. Control hearts were perfused for 75 min without being made ischemic. During ischemia Mgr (mmol/l) increased from 0.76 +/- 0.20 to 4.34 +2- 1.99 in the rat hearts, and from 0.72 +/- 0.22 to 2.18 +/- 1.06 (15 min) and 2.35 +/- 1.26 (20 min) in the rabbit hearts. During reperfusion Mgr in the three groups returned to the level of the control hearts within 7.5 min, and LVDP within 25 min. At the end of the reperfusion period ATP content amounted to 56 +/- 17% (rat hearts), 66 +/- 10% (rabbit hearts; 15 min ischemia group) and 61 +/- 7% (rabbit hearts; 20 min ischemia group) of the pre-ischemic levels. The results confirm that in vitro stunning is a short-lived phenomenon and indicate that an increased Mgr is not involved in this temporary mechanical dysfunction.

Adenosine Triphosphate↗
PubMed1992

Organization of inferior olivary projections to the flocculus and ventral paraflocculus of the rat cerebellum.

The climbing fiber projection to the rat flocculus and adjacent ventral paraflocculus was investigated by using Phaseolus vulgaris-leucoagglutinin as an anterograde and horseradish peroxidase as a retrograde tracer. Large injections of horseradish peroxidase in the flocculus and ventral paraflocculus indicated that the climbing fibers to this region are derived exclusively from any of the following contralateral olivary regions: the dorsal cap of Kooy, the ventrolateral outgrowth, the caudal half of the ventral leaf of the principal olive near its lateral bend, and the rostral pole of the medial accessory olive. Subsequent anterograde and retrograde studies with small injections demonstrated that the latter area projects to the C2 zone, which runs caudally in the ventral paraflocculus and enters the caudal most aspect of the flocculus. The ventral leaf of the principal olive is connected to a D zone in the cerebellar hemisphere and paraflocculus, which, upon entering the ventral paraflocculus, divides into a caudal and rostral strip, termed FD and FD', respectively. The dorsal cap and the ventrolateral outgrowth each project to two distinct zones in the flocculus and part of the ventral paraflocculus. Two floccular zones, which are continuous with the parafloccular FD and FD' zones, receive their climbing fibers from the ventrolateral outgrowth. Two other zones, (FE and FE') receive their climbing fibers from the dorsal cap. The FE' zone is found at the rostral pole of the flocculus and is followed caudalwards by the FD', FE, FD, and C2 zones, respectively. The rostromedial part of the dorsal cap is connected to the continuation of the FE zone into the ventral paraflocculus. The observation that the dorsal cap and the ventrolateral outgrowth are both connected to a set of two alternating zones of floccular/ventral parafloccular Purkinje cells is in agreement with recent studies in the rabbit, and suggests that these zones reflect functionally distinct and discrete units related to specific aspects of visuomotor control.

Animals↗
PubMed1992

Postischaemic metabolic and functional recovery of rat heart after transient reperfusion with various low Ca2+ concentrations.

OBJECTIVE: The effects of transient low Ca2+ reperfusion after ischaemia on metabolic and functional recovery were studied in isolated rat hearts. METHODS: 31P nuclear magnetic resonance (NMR) was used to monitor creatine phosphate, ATP, intracellular inorganic phosphate (Pi), and intracellular pH during control perfusion (15 min), total ischaemia (30 min), and reperfusion (30 min). During early reperfusion (0-10 min) perfusate [Ca2+] amounted to 1.3 (control group), 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7 mmol.litre-1. During late reperfusion (10-30 min) perfusate [Ca2+] was 1.3 mmol.litre-1. Isolated rat hearts were used and perfused according to Langendorff. RESULTS: Recovery of creatine phosphate during early reperfusion was partly abolished during late reperfusion in the 0.1-0.4 mmol.litre-1 groups (p < 0.01). In the 0.1 mmol.litre-1 group creatine phosphate content after 30 min reperfusion was lower (p < 0.05) than in the control group. Recovery of ATP during early reperfusion in the 0.3 mmol.litre-1 group was better than in the control group (p < 0.01). After 30 min reperfusion ATP recovery was better in the 0.3 mmol.litre-1 group (p < 0.01) and worse in the 0.1 mmol.litre-1 group (p = 0.05) than in the control group. Decline of Pi during early reperfusion was more pronounced in the 0.2 and 0.3 mmol.litre-1 groups (p < 0.01) and in the 0.5 and 0.6 mmol.litre-1 groups (p < 0.05) than in the control group. In the 0.3 and 0.4 mmol.litre-1 groups, Pi after 30 min reperfusion was higher (p < 0.05) than after 10 min reperfusion. After 30 min reperfusion left ventricular developed pressure, measured with an intraventricular balloon, was lower in the 0.1 mmol.litre-1 group (p < 0.01) than in the control group. CONCLUSIONS: The data show that under the experimental conditions used successive postischaemic reperfusion with 0.1 and 1.3 mmol.litre-1 Ca2+ resulted in poorer metabolic and functional recovery of the hearts than continuous reperfusion with 1.3 mmol.litre-1 Ca2+. Postischaemic reperfusion with 0.1 mmol.litre-1 Ca2+ may predispose the heart to a mild calcium paradox. Successive reperfusion with 0.3 and 1.3 mmol.litre-1 Ca2+ was optimal in terms of ATP recovery but did not result in an increased recovery of left ventricular developed pressure.

Adenosine Triphosphate↗
PubMed1992

Possible mechanisms of the protective effect of pretreatment with anipamil in ischemic-reperfused isolated rat hearts.

Rats were given anipamil (5 mg/kg) or glucose, intraperitoneally twice daily for 5 days. During this period the mean arterial blood pressure and heart rate were measured daily. The heart was then isolated and perfused. Energy metabolism and intracellular pH were monitored by 31P nuclear magnetic resonance spectroscopy during 30 minutes of ischemia followed by 30 minutes of reperfusion, with a simultaneous isovolumetric measurement of left ventricular contraction. Myocardial norepinephrine and glycogen were assayed immediately after excision of the heart, after 15 minutes oxygenated perfusion, at the end of ischemia and at the end of reperfusion. Metabolic and functional recovery during reperfusion were significantly better in hearts pretreated with anipamil (p less than 0.0005 vs controls). However, protection was not preceded by an effect on mean arterial pressure or heart rate in vivo, or a negative inotropic effect during control perfusion of the isolated hearts. There was no energy sparing effect during ischemia; but intracellular pH during ischemia stabilized at a higher level (p less than 0.0005 vs controls). Myocardial norepinephrine and glycogen stores were not decreased by pretreatment with anipamil, and their release or degradation due to ischemia and reperfusion were also not different from controls. Commonly known mechanisms of myocardial protection by calcium antagonists fail to explain the protection by pretreatment with anipamil as observed in our experiments, and alternative mechanisms are to be considered.

Animals↗
PubMed1991

Chronic cardiotoxicity of adriamycin studied in a rat model by 31P NMR.

Adriamycin induced cardiotoxicity is, among other factors, characterized by an impairment of mitochondrial function and altered energy metabolism. The possible merits of 31P NMR in timely detection of this cardiotoxicity were studied in perfused hearts of chronically treated rats after cumulative doses of 6, 8, 10, 12 and 13 mg adriamycin/kg body wt and compared to histological evaluation. After high cumulative doses the Phosphocreatine (PCr)/ATP ratio was significantly decreased in the hearts of treated animals, compared to the control animals (1.65 +/- 0.13 vs. 2.47 +/- 0.36 (p less than 0.001) at 12 mg/kg and 1.92 +/- 0.22 vs. 2.37 +/- 0.15 (p less than 0.01) at 13 mg/kg adriamycin, respectively). This decrease coincides with a sudden increase in the histological score from 2.0 at 10 mg/kg to 8.0 at 12 mg/kg adriamycin on a scale of 10.0. The Pi/PCr ratio, coronary flow and rate pressure product (RPP) of the isolated hearts of treated animals were not significantly different from controls. When heart rates were increased, parallel changes in PCr/ATP ratio, Pi/PCr ratio, RPP and coronary flow were observed in both control and treated groups, except for the 12 mg/kg adriamycin group in which pacing failed to increase RPP. In addition, in this group the Pi/PCr ratio at higher heart rates was significantly increased (p less than 0.001) compared to controls. At 13 mg/kg similar effects were observed but less pronounced. The decreased PCr/ATP ratio may indicate an increased ADP concentration and altered regulation of energy metabolism. Differences between control and treated groups in RPP and Pi/PCr ratio during pacing may also be related to cardiotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1991

Intracellular sodium during ischemia and calcium-free perfusion: a 23Na NMR study.

Accumulation of sodium-ions (Na+) in myocardial cells during both ischemia and calcium (Ca2+)-free perfusion has been suggested to play an important role in the damage occurring during subsequent reperfusion and calcium repletion, respectively. We have used 23Na NMR spectroscopy in combination with shift reagents to determine intracellular Na(+)-concentration [( Na+]i) in isolated rat hearts during either control perfusion followed by ischemia and reperfusion, or during control perfusion, Ca(2+)-free perfusion and subsequent ischemia. [Na+]i during control perfusion was found to be 10.5 +/- 0.6 mmol/l. During 30 min of ischemia [Na+]i rose substantially to 25.0 +/- 3.2 mmol/l. During 15 min of reperfusion [Na+]i initially decreased, but leveled off after approximately 3 min and was 17.9 +/- 3.7 mmol/l at the end of the reperfusion period. Most surprisingly, however, no significant increase of [Na+]i was observed during 30 min of Ca(2+)-free perfusion, although severe calcium paradox damage was shown to occur under the used conditions, when calcium was readmitted to the heart. The absence of a rise of [Na+]i during Ca(2+)-free perfusion was substantiated when during subsequent ischemia a similar rise of [Na+]i was observed as during ischemia without previous Ca(2+)-depletion. We conclude that an increased [Na+]i during Ca(2+)-depletion is not a prerequisite for the calcium paradox to occur, but that increased [Na+]i during ischemia may influence the subsequent reperfusion damage through Na(+)-Ca2+ exchange.

Animals↗
PubMed1990

Intracellular labeling of neurons in the medial accessory olive of the cat: I. Physiology and light microscopy.

This study is the first of three reports on the detailed morphology of horseradish peroxidase injected neurons in the medial accessory olive of the cat. Intracellular, in vivo recordings of olivary cells were made and their response to mesodiencephalic stimulation was tested. In 44 units a short latency action potential could be recorded, which was very suggestive of a monosynaptic excitatory pathway. The short latency response was frequently followed by a long latency (mean 188 msec) or rebound action potential. Recordings were followed by intracellular iontophoresis of horseradish peroxidase. A total of 21 neurons, all located within the medial accessory olive were chosen for morphological analysis. Cells could be divided into two categories on the basis of their overall morphological appearance. Type I cells (n = 5) had sparsely branching dendrites that radiated away from the soma and were usually found in the caudal part of the medial accessory olive. The axon usually originated from the soma. Type II cells (n = 16) were located more rostrally. They had larger cell bodies with dendrites that ramified extensively, forming a globular structure (mean diam. 338 microns). The axon usually originated from a first order dendrite. No recurrent axon collaterals were observed on either type I or II cells. Both cell types carried long and complex spiny appendages; however, they were most numerous on the second and higher order dendrites of type II cells. Since the soma of these cells is usually not found in the centre of its dendritic field, even if the cell is located in the center area of the neuropil, it is suggested that the dendritic trees of up to 100 neurons may be intricately interwoven, establishing clusters with intensive intercommunication by means of dendritic gap junctions. The abundance, length and complexity of the spiny appendages suggest an important role in this process, but may also be relevant instruments in enhancing the computational capabilities of these neurons, especially in time sensitive processes. When relating the physiological and the morphological results, it was noted that both type I and type II cells could respond to mesodiencephalic stimulation and were both able to trigger a rebound action potential. No significant correlations were found between cell size and the latency of the rebound.

Action Potentials↗
PubMed1990

Intracellular labeling of neurons in the medial accessory olive of the cat: II. Ultrastructure of dendritic spines and their GABAergic innervation.

In order to describe the morphology of dendritic spines of identified neurons in the cat inferior olive together with their gamma-aminobutyric acid (GABA) synaptic input, a technique was used combining intracellular labeling of horseradish peroxidase with postembedding gold-immunocytochemistry. With this technique physiologically identified olivary cells were reconstructed with the light microscope, and the horseradish peroxidase reaction product and immunogold labeling were subsequently examined in serial sections at the ultrastructural level. In addition, a degenerating neuron was observed, resulting in a triple labeling in single ultrathin sections. Quantitative and three-dimensional analysis showed that the dendritic spines were composed of long, thin stalks ending in one or more spine heads. The spines of cells located in the caudal half of the medial accessory olive (type I cells, characterized by dendrites which run away from the soma) were found to be less complex than those of cells located rostrally in this olivary subnucleus (type II cells, characterized by dendrites which tend to turn back towards the soma). Most, if not all, of the spines of both cell types were located within glomeruli. On average, the spines within individual glomeruli originated from 6 different dendrites (with a maximum of 8). Different spines within the same glomerulus were never derived from different dendrites of the same olivary neuron, but single spines frequently gave rise to several spine heads, which could be located either within different glomeruli or inside a single glomerulus. The glomerular spine heads originating from the same spine were rarely located near one another. All spines and most of the spine heads were contacted by both GABAergic and non-GABAergic terminals. Most of the GABAergic terminals contained pleomorphical vesicles and displayed symmetric synapses whereas the non-GABAergic terminals showed usually round to oval vesicles and asymmetric synapses.

Animals↗
PubMed1990

Intracellular labeling of neurons in the medial accessory olive of the cat: III. Ultrastructure of axon hillock and initial segment and their GABAergic innervation.

The gamma-aminobutyric acid (GABA) synaptic input of identified axons in the cat inferior olive was studied by use of combination of intracellular labeling with horseradish peroxidase and postembedding gold-immunocytochemistry. With this technique olivary cells were physiologically identified and light microscopically reconstructed, and the horseradish peroxidase reaction product and the immunogold labeling were subsequently simultaneously visualized for electron microscopic investigation with the use of serial ultrathin sections. The axons of cell type I (characterized by dendrites which radiate away from the cell body) originated from the soma, whereas those of type II neurons (characterized by dendritic trees which curve back towards the soma) were derived from a primary dendrite. The axons of olivary neurons stand out by the length of their axon hillock (up to 21 microns) and initial segment (up to 40 microns). The hillock forms various spiny appendages which were located within glomeruli together with dendritic spines of other olivary neurons. Axonal spines of type II neurons were more numerous and complex looking than those of type I. The axonal spines, the shaft of the axon hillock, and the transition between the hillock and initial segment were primarily innervated by GABAergic terminals (65%) but non-GABAergic terminals (35%) were present as well. The terminals apposed to the axons of type I neurons contacted mainly the axonal shafts, whereas most of the terminals adjacent to the axons of type II neurons established synaptic contacts with the axonal spines. The initial segments were largely devoid of synaptic input. Distally, the initial segment acquired a myelin sheath.

Animals↗