Motoneuron firing properties are modified by trans-spinal direct current stimulation in rats.

Spinal polarization evoked by direct current stimulation [trans-spinal direct current stimulation (tsDCS)] is a novel method for altering spinal network excitability; however, it remains not well understood. The aim of this study was to determine whether tsDCS influences spinal motoneuron activity. Twenty Wistar rats under general pentobarbital anesthesia were subjected to 15 min anodal (n = 10) or cathodal (n = 10) tsDCS of 0.1 mA intensity, and the electrophysiological properties of their motoneurons were intracellularly measured before, during, and after direct current application. The major effects of anodal intervention included increased minimum firing frequency and the slope of the frequency-current (f-I) relationship, as well as decreased rheobase and currents evoking steady-state firing (SSF). The effects of cathodal polarization included decreased maximum SSF frequency, decreased f-I slope, and decreased current evoking the maximum SSF. Notably, the majority of observed effects appeared immediately after the current onset, developed during polarization, and outlasted it for at least 15 min. Moreover, the effects of anodal polarization were generally more pronounced and uniform than those evoked by cathodal polarization. Our study is the first to present polarity-dependent, long-lasting changes in spinal motoneuron firing following tsDCS, which may aid in the development of more safe and accurate application protocols in medicine and sport. NEW & NOTEWORTHY Trans-spinal direct current stimulation induces significant polarity-dependent, long-lasting changes in the threshold and firing properties of spinal motoneurons. Anodal polarization potentiates motoneuron firing whereas cathodal polarization acts mainly toward firing inhibition. The alterations in rheobase and rhythmic firing properties are not restricted to the period of current application and can be observed long after the current offset.

"Extracorporeal Membrane Oxygenation for Greater Poland" Program: How to Save Lives and Develop Organ Donation?

The "ECMO for Greater Poland" program takes full advantage of the extracorporeal membrane oxygenation (ECMO) perfusion therapy opportunities to promote the health of the 3.5 million inhabitants in the region. The main implementation areas are treatment of patients with hypothermia; severe reversible respiratory failure (RRF); critical states resulting in heart failure, that is, cardiac arrest, cardiogenic shock, or acute intoxication; and promotion of the donor after circulatory death (DCD) strategy in selected organ donor cases, after unsuccessful life-saving treatment, to achieve organ recovery. This organizational model is complex and expensive, so we used advanced high-fidelity medical simulation tests to prepare for real-life experience. Over the course of 4 months we performed scenarios including "ECMO for DCD," "ECMO for extended cardiopulmonary resuscitation," "ECMO for RRF," and "ECMO in hypothermia." Soon after these simulations, Maastricht category II DCD procedures were performed involving real patients and resulting in 2 successful double kidney transplantations for the first time in Poland. One month later we treated 2 hypothermia patients (7 adult patients with heart failure and 5 patients with reversible respiratory failure) with ECMO for the first time in the region. Fortunately, we have discovered an important new role of medical simulation. It can be used not only for skills testing but also as a tool to create non-existing procedures and unavailable algorithms. The result of these program activities will promote the care and treatment of patients in critical condition with ECMO therapy as well as increase the potential organ pool from DCDs in the Greater Poland region of Poland.

Adaptations of motoneuron properties to chronic compensatory muscle overload.

The aim of the study was to determine whether chronic muscle overload has measurable effect on electrophysiological properties of motoneurons (MNs), and whether duration of this overload influences intensity of adaptations. The compensatory overload was induced in the rat medial gastrocnemius (MG) by bilateral tenotomy of its synergists (lateral gastrocnemius, soleus, and plantaris); as a result, only the MG was able to evoke the foot plantar flexion. To assure regular activation of the MG muscle, rats were placed in wheel-equipped cages and subjected to a low-level treadmill exercise. The intracellular recordings from MG motoneurons were made after 5 or 12 wk of the overload, and in a control group of intact rats. Some of the passive and threshold membrane properties as well as rhythmic firing properties were considerably modified in fast-type MNs, while remaining unaltered in slow-type MNs. The significant changes included a shortening of the spike duration and the spike rise time, an increase of the afterhyperpolarization amplitude, an increase of the input resistance, a decrease of the rheobase, and a decrease of the minimum current necessary to evoke steady-state firing. The data suggest higher excitability of fast-type MNs innervating the overloaded muscle, and a shift towards electrophysiological properties of slow-type MNs. All of the adaptations could be observed after 5 wk of the compensatory overload with no further changes occurring after 12 wk. This indicates that the response to an increased level of chronic activation of MNs is relatively quick and stable.

Concomitant changes in afterhyperpolarization and twitch following repetitive stimulation of fast motoneurones and motor units.

The study aimed at determining changes in a course of motoneuronal afterhyperpolarization (AHP) and in contractile twitches of motor units (MUs) during activity evoked by increasing number of stimuli (from 1 to 5), at short interspike intervals (5 ms). The stimulation was applied antidromically to spinal motoneurones or to isolated axons of MUs of the medial gastrocnemius muscle within two separate series of experiments on anesthetized rats. Alterations in the amplitude and time parameters of the AHP of successive spikes were compared to changes in force and time course of successive twitches obtained by mathematical subtraction of tetanic contractions evoked by one to five stimuli. The extent of changes of the studied parameters depended on a number of applied stimuli. The maximal modulation of the AHP and twitch parameters (a prolongation and an increase in the AHP and twitch amplitudes) was typically observed after the second pulse, while higher number of pulses at the same frequency did not induce so prominent changes. One may conclude that changes observed in parameters of action potentials of motoneurons are concomitant to changes in contractile properties of MU twitches. This suggests that both modulations of the AHP and twitch parameters reflect mechanisms leading to force development at the beginning of MU activity.

The influence of a 5-wk whole body vibration on electrophysiological properties of rat hindlimb spinal motoneurons.

The study aimed at determining the influence of a whole body vibration (WBV) on electrophysiological properties of spinal motoneurons. The WBV training was performed on adult male Wistar rats, 5 days a week, for 5 wk, and each daily session consisted of four 30-s runs of vibration at 50 Hz. Motoneuron properties were investigated intracellularly during experiments on deeply anesthetized animals. The experimental group subjected to the WBV consisted of seven rats, and the control group of nine rats. The WBV treatment induced no significant changes in the passive membrane properties of motoneurons. However, the WBV-evoked adaptations in excitability and firing properties were observed, and they were limited to fast-type motoneurons. A significant decrease in rheobase current and a decrease in the minimum and the maximum currents required to evoke steady-state firing in motoneurons were revealed. These changes resulted in a leftward shift of the frequency-current relationship, combined with an increase in slope of this curve. The functional relevance of the described adaptive changes is the ability of fast motoneurons of rats subjected to the WBV to produce series of action potentials at higher frequencies in a response to the same intensity of activation. Previous studies proved that WBV induces changes in the contractile parameters predominantly of fast motor units (MUs). The data obtained in our experiment shed a new light to possible explanation of these results, suggesting that neuronal factors also play a substantial role in MU adaptation.

Advantages of bilayered vascular grafts for surgical applicability and tissue regeneration.

Nanofibrous scaffolds are part of an intense research effort to design the next generation of vascular grafts. With electrospinning, the production of micro- and nano-fiber-based prostheses is simple and cost effective. An important parameter for tissue regeneration in such scaffolds is pore size. Too small pores will impede cell infiltration, but too large pores can lead to problems such as blood leakage. In this study, bilayered grafts were made by electrospinning a high-porosity graft with a low-porosity layer on either the luminal or the adventitial side. Grafts were characterized in vitro for fiber size, pore size, total porosity, water and blood leakage, mechanical strength, burst pressure and suture retention strength, and were evaluated in vivo in the rat abdominal aorta replacement model for 3 and 12 weeks. In vitro blood leakage through these bilayered grafts was significantly reduced compared with a high-porosity graft. All grafts had an excellent in vivo outcome, with perfect patency and no thrombosis. Cell invasion and neovascularization were significantly reduced in the grafts with a low-porosity layer on the adventitial side, and there was no significant difference between the grafts in endothelialization rate or intimal hyperplasia. By tailoring the microarchitecture of biodegradable vascular prostheses, it is therefore possible to optimize the scaffold for tissue regeneration while preventing blood leakage, and thus facilitating applicability in the clinic.

Doublet of action potentials evoked by intracellular injection of rectangular depolarization current into rat motoneurones.

A doublet of action potentials is frequently observed at the beginning of motoneuronal discharge patterns and its appearance leads to a considerable increase in the motor unit force. The aims of this study were (1) to determine the relationship between the intensity of rectangular depolarization currents injected into motoneurones and their ability to generate doublets and (2) to evaluate the influence of the initial doublets on changes in motoneuronal firing frequency. Experiments were performed on anesthetized rats, and recordings were taken from motoneurones located in the L4-L5 segments of the spinal cord. The depolarization current necessary to evoke the initial doublet of action potentials was measured and expressed in multiples of the rheobase. A gradual increase in the intensity of current injected into motoneurones resulted in initial doublets in 80% of the cases studied, at doublet threshold ranges between 1.25 and 4.0 times the rheobase. This suggests that doublets are an effect of strong synaptic excitation of motoneurones that may precede a sudden change in force during a movement. Moreover, in the great majority of the studied motoneurones, this initial doublet caused changes in the subsequent firing rate by the prolongation of the first interspike interval.

Octogenarians undergoing combined aortic valve replacement and myocardial revascularization: perioperative mortality and medium-term survival.

OBJECTIVE: Aim of the study was to answer the question whether the mortality and morbidity of octogenarians undergoing combined aortic valve replacement and myocardial revascularization (AVR + CABG) is higher than that of younger patients. PATIENTS AND METHODS: Between 01/1995 and 12/2002, 242 patients underwent AVR + CABG in our institution. 37 patients were older than 80 years (16 male, 21 female, median pressure gradient over the aortic valve: 53 mmHg, median EF: 62%), 205 patients were younger than 80 years (133 male, 72 female, median gradient 48 mmHg, median EF: 61%). NYHA class, aortic valve area and valve calcification were worse in the 80+ group. Biological valve prostheses were implanted in 94.6% of the older and in 45.4% of the younger patients (p < 0.001). RESULTS: Perioperative complications occurred more often (p = 0.0188) in the 80+ group (86.5% experienced 1 or more complications) than in the 80- group (66.3%). Similarly, the MACE (Major Adverse Cardiovascular Events) rate was higher (p = 0.0448) in the 80+ group than in the 80- group. Bleeding occurred (p = 0.092) more often in younger (9.3%) than in older (0%) patients, while renal insufficiency was more frequent (p = 0.0164) in older (21.6%) than in younger patients (7.8 %). The 30-day mortality was higher (p = 0.0045) in older (21.6%) than in younger patients (5.8%). Multivariate analysis revealed an odds ratio for early death of 2.9 (CI 1.014-8.397) for patients older than 80 years. The late death rate within the first 5 years after surgery was comparable in both groups (80- group 24.4%, 80+ group 24.3%). Postoperative quality of life was significantly worse in the 80+ group in 4 out of 8 functions. CONCLUSIONS: Octogenarians undergoing AVR + CABG have a relatively high perioperative complication rate and mortality, but show a stable medium-term survival. The perioperative complication rate is higher in older than in younger patients, and the postoperative quality of life with regard to bodily functions is acceptable but significantly worse than that of younger patients.

Summation of afterhyperpolarization after a doublet in fast motoneurones of the rat spinal cord.

Motoneurones located in lumbar segments (L4-L5) of the rat spinal cord were activated antidromically by stimulation of the sciatic nerve. Records following a single pulse and double stimuli were collected from fast motoneurones and in each case voltage and time parameters of the action potential and afterhyperpolarization (AHP) were compared to respective values calculated for a simulated doublet - obtained by mathematical summation of two individual single potentials. The most prominent differences between experimentally recorded and simulated potentials concerned spike duration and the AHP half-decay times, with significantly lower values obtained for the simulated doublets. Tendencies for a higher AHP amplitude, shorter AHP peak time and higher AHP area were observed in mathematically modeled doublets, though no statistical differences were present in comparison to experimental data. Results indicated a non-linear summation of the AHP after double stimuli running in a short interval. These observations suggest that alterations in the generation of the AHP, mainly based on the sustained activity of K(Na+) channels, influence time-intervals in motoneuronal discharge pattern and this way force development of individual motor units during muscle activity.

Interspecies differences in the force-frequency relationship of the medial gastrocnemius motor units.

Single, functionally isolated motor units were studied in the medial gastrocnemius (MG) muscle of cats and rats. Axons of their motoneurons were stimulated with trains of pulses at frequencies increasing from 1 to 150 Hz and forces developed by muscle fibers were measured and force-frequency curves were compared between species. The following observations were made: (1) the most steep parts of curves (related to unfused tetani of motor units) begun at lower frequencies of stimulations in all types of feline motor units, (2) for fast motor units, the same relative values of force of unfused tetani were achieved at significantly lower frequencies of stimulations in the cat than in the rat. Twitch time parameters of both species influenced the course of force-frequency curves. It was showed that the contraction times of feline units varied in the wide range (21-81 ms), and these units reached 60% of the maximum force at stimulation frequencies between 10 and 38 Hz. On the other hand, contraction times of rat units ranged from 10 to 34 ms, whereas stimulation frequencies necessary to reach 60% of the maximum force varied considerably, from 12 to 65 Hz. The correlations between the above parameters were found for motor units of each species. However, the regression lines drown for the collected population of cat and rat units did not form linear continuity. Thus it seems that interspecies differences in the twitch contraction times do not fully explain different force-frequency relationships in mammalian skeletal muscles.

Interspecies differences of motor units properties in the medial gastrocnemius muscle of cat and rat.

The purpose of the study was to analyze the interspecies differences of motor unit contractile properties in two most frequently studied mammals: cats and rats. A total sample of 166 motor units (79 in cats and 85 in rats) was investigated in the medial gastrocnemius muscle. Considerable differences were found in composition of the studied muscle. In cats, fast fatigable, fast resistant and slow units formed 68, 18 and 14% of the investigated population, whereas in rats 36, 52 and 12%, respectively. The contraction and relaxation times of motor units in the cat muscle were evidently longer than in the rat and the border values for fast/slow motor units division in these species were 44 and 20 ms, respectively. The mean values of twitch and tetanic forces appeared to be 7-8 times lower in rats, for fast, while 2-5 times for slow motor units. Also variability between the strongest and the weakest units within each type revealed differences 10-60 times in cats, whereas only 3.5-14 times in rats. The summation of twitches into tetanus for fast units was comparable in both species, but for S units was evidently more effective in the cat. In fast motor units' tetanic contractions evident interspecies differences concerned sag appearance and profiles of unfused tetani of FF and FR units. Differences in contractile properties described in the study may depend on the size, number and innervation ratio of motor units in the muscle of cat and rat, as well as their biochemical variability. Differences in composition of motor unit types and uneven mechanisms of force development may reflect biological adaptation to variable behaviour of cats and rats.

Convergence of forelimb afferent actions on C7-Th1 propriospinal neurones bilaterally projecting to sacral segments of the cat spinal cord.

Propriospinal neurones located in the cervical enlargement and projecting bilaterally to sacral segments of the spinal cord were investigated electrophysiologically in eleven deeply anaesthetized cats. Excitatory or inhibitory postsynaptic potentials from forelimb afferents were recorded following stimulation of deep radial (DR), superficial radial (SR), median (Med) and ulnar (Uln) nerves. 26 cells were recorded from C7, 22 from C8 and 3 from Th1 segments. The majority of the cells were located in the Rexed's laminae VIII and the medial part of the lamina VII. In 10 cases no afferent input from the forelimb afferents was found. In the remaining neurones effects were evoked mostly from DR (88%) and Med (63%), less often from SR (46%) and Uln (46%). Inhibitory actions were more frequent than excitatory. The highest number of IPSPs was evoked from high threshold flexor reflex afferents (FRA)--all connections were polysynaptic. However, inhibitory actions were often evoked from group I or II muscle afferents (polysynaptic or disynaptic) and, less frequently, from cutaneous afferents (mostly polysynaptic). Di- or polysynaptic IPSPs often accompanied monosynaptic EPSPs from group I or II muscle afferents. Disynaptic or polysynaptic EPSPs from muscle and cutaneous afferents were also recorded in many neurones, while polysynaptic EPSPs from FRA were observed only exceptionally. Various patterns of convergence in individual neuronal subpopulations indicate that they integrate different types of the afferent input from various muscle and cutaneous receptors of the distal forelimb. They transmit this information to motor centers controlling hind limb muscles, forming a part of the system contributing to the process of coordination of movements of fore--and hind--limbs.

Thyroid hormones levels in infants during and after cardiopulmonary bypass with ultrafiltration.

OBJECTIVE: The aim of this study was to find out if infants after cardiopulmonary bypass develop non-thyroidal illness and if illness severity after cardiopulmonary bypass depends on hormone concentration in ultrafiltrate. METHODS: Thyroid hormone status was assessed in 20 infants with congenital heart defects undergoing cardiac surgery (age range 7 days-11 months). Blood samples were collected preoperatively, during cardiopulmonary bypass, after cardiopulmonary bypass, and also postoperatively in 1, 2, 3, and 8 day after cardiac surgery. Plasma thyrotropin, thyroxine, free thyroxine, triiodothyronine, free triiodothyronine and reverse triiodothyronine were measured in blood samples and also in ultrafiltrate. RESULTS: All patients had reduction in serum thyrotropin, thyroxine, free thyroxine, triiodothyronine, free triiodothyronine, and elevation of reverse triiodothyronine after cardiac surgery. In all patients we performed ultrafiltration. Patients were divided in to two groups. (with and without prolonged recovery). In the group of patients with prolonged recovery we noticed significantly higher amount of triiodothyronine per kilogram body weight. One of these patients died. The average level of total thyroxine decreased from the level 126 nmol/l before bypass to the minimal level 73 nmol/l after bypass, free thyroxine from the level 18 pmol/l before bypass to the minimal level 12 pmol/l after bypass. The average level of total triiodothyronine decreased from the level 1.54 nmol/l before bypass to the minimal level 0.42 nmol/l after bypass, free triiodothyronine from the level 6.12 pmol/l before bypass to the minimal level 3.21 pmol/l after bypass. The average level of TSH decreased from the level 4.31 mU/l before bypass to the level 0.64 mU/l after bypass. The average level of reverse-triiodothyronine increase from the level 0.83 nmol/l before bypass to the maximal level 1.94 nmol/l after bypass. CONCLUSIONS: We conclude that non-thyroidal illness occurs in all infants after cardiopulmonary bypass. The amount of free triiodothyronine that is filtrated during cardiopulmonary bypass may influence postoperative recovery.

Neurones in the cervical enlargement of the cat spinal cord antidromically activated from sacral segments and the inferior cerebellar peduncle.

The electrophysiological investigation of neurones located in the cervical enlargement of the spinal cord was performed in eight-chloralose anaesthetized cats. Neurones were recorded intracellularly or extracellularly and identified by antidromic stimulation. The main purpose of the study was to test whether these neurones give off collateral branches ascending to the inferior cerebellar peduncle and descending to the sacral segments (S1/S2). Recordings were made from 78 neurones located in medial and central parts of Rexed's laminae VII and VIII of C6/C7 segments. Four subpopulations could be distinguished from their patterns of propriospinal or supraspinal projections: (a) ascending/descending neurones with axons ascending to RB and descending to S1/S2 (23%); (b) ascending/descending neurones projecting to RB and the level of Th13 (14%); (c) propriospinal neurones descending to Th13 (15%); (d) propriospinal neurones descending to S1/S2 (48%). Within these groups, ipsilateral, contralateral and bilateral descending projections were observed. The mean axonal conduction velocities for descending and ascending collaterals of bidirectional neurones were 59 and 39 m/s, respectively. Results suggest that parallel transmission of information to supraspinal and spinal centres plays an important role in the process of movement coordination.

Electrophysiological investigation of spino-olivary projections originating from sacral segments of the cat spinal cord.

Ascending projections of sacral spinal cord neurones (S1-S2) to the dorsal accessory olivary nucleus (DAO) were electrophysiologically investigated in 3 adult cats under deep alpha-chloralose anaesthesia. Antidromic action potentials were recorded extracellularly from 19 cells following stimulation of their axons in both the contralateral dorsal accessory olivary nucleus (coDAO) and the contralateral lateral funiculus at the level of lower thoracic segments (Th13). Two groups of neurones were identified in the gray matter of S1-S2 segments: one distributed in the medial part of Rexed's laminae VI and VII (n = 5), the other located in the ventromedial part of lamina VIII (n = 14). Axonal conduction velocities of neurones investigated were comprised in the range 32-55 m/s. A significant decrease of conduction velocity was observed in each case when distal and proximal parts of the axon were compared. Our research confirmed anatomical data concerning spino-olivary neurones originating from sacral segments. However, we suggest that axons of this pathway give off collaterals to other spinal or supraspinal centres.

Bidirectional neurones in the cervical enlargement of the cat spinal cord with axons descending to sacral segments and ascending to the cerebellum and the lateral reticular nucleus.

Neurones located in cervical segments (C6/C7) of the spinal cord were investigated electrophysiologically in cats deeply anaesthetized with alpha-chloralose. Extracellular recordings of antidromic action potentials were performed in order to establish whether long descending propriospinal neurones projecting to sacral segments could have collateral axonal branches ascending to supraspinal centres. The effects of stimulation of the lateral reticular nucleus (LRN) and the inferior cerebellar peduncle (restiform body, RB), as well as the thirteenth thoracic (Th13) and sacral (S1/S2) segments of the spinal cord were tested in 93 cells. Two main groups of cells were identified: 54 % of the total sample were classified as purely propriospinal and 46 % as bidirectional neurones. Various patterns of projections, as well as the ipsi-, contra- or bilateral courses of axons in the lateral funiculi of the spinal cord, enabled several types of neurones to be distinguished within the above groups. Comparison between particular types showed no significant difference with respect to location in the grey matter (predominantly Rexed's laminae VII-VIII) and the conduction velocities of descending axons. However, the mean axonal conduction velocities of branches ascending to LRN and/or RB were significantly lower in comparison to those measured for spinal collaterals. The hypothetical function of the neurones examined is discussed. Since the same information can be conveyed simultaneously by these branching neurones to lower spinal segments and supraspinal centres, an integrative role in the system of motor control is suggested.

Spinoreticular neurons in the second sacral segment of the feline spinal cord.

In continuation of previous electrophysiological studies on the location of ascending tract neurones within the second sacral segment of the feline spinal cord, the spinoreticular projections of these neurones have been investigated. Following electrical stimulation of the axonal terminals of 37 spinoreticular neurons via a tungsten electrode placed stereotactically in the contralateral nucleus reticularis gigantocellularis, antidromic potentials from their cell bodies were recorded with glass microelectrodes both extra- and intracellularly. The axons of these neurones were additionally excited from the dorsolateral funiculi of the contralateral (n = 37) and ipsilateral (n = 30) side at the lowermost thoracic spinal level. The latencies of antidromic excitation from the brainstem to the second sacral segment ranged from 3.2 to 11.8 ms (mean, 5.9 ms), whereas the corresponding axonal conduction velocities were between 27.1 and 100 m/s. The neurones examined in this study were found to be situated in the medial lamina VII of Rexed and the area adjacent to the central canal (n = 13), the medial lamina VIII (n = 12), medial laminae V and VI (n = 10) and in laminae II and III (n = 2). Three medium-sized (40-60 microm) of triangular- or oval-shaped neurones were visualized in medial laminae VII and VIII following the intracellular labelling with horseradish peroxidase.

Divergence of lamina VII and VIII neurones of S1 and S2 segments of the cat's spinal cord to the cerebellum and the reticular formation.

Cerebellar and reticular projections of neurones located in sacral segments of the spinal cord were electrophysiologically investigated in alpha-chloralose anaesthetized cats. Antidromic action potentials were recorded following stimulation of the contralateral restiform body (coRB), contralateral gigantocellular nucleus (coGRN) as well as ipsi- and contralateral lateral funiculus of the 13th thoracic segment (iTh13 and coTh13). Eighty-seven neurones were found in the medial lamina VII and lamina VIII of the gray matter of S1 and S2 segments. Their axons ascended in lateral funiculi on the contralateral side and in 46 cases also on the ipsilateral side of the spinal cord. A projection to coRB was found in 20 neurones, to coGRN in 10 and dual projections to both coRB and coGRN in 20 neurones. Axons of the remaining 37 cells were found to ascend to the level of Th13 only. Conduction velocities of neurones investigated were comprised in the range 35-83 m/s and no significant differences were found between particular groups. However, an evident decrease in conduction was observed in most neurones when comparing proximal to distal parts of their axons, suggesting the possibility of more extensive divergence than indicated in this study. The pattern of projections revealed that the information from the periphery is conveyed in parallel to various supraspinal and possibly also spinal centres.

The electrophysiological study of axonal branching of the C6-C7 neurones of the cat's spinal cord projecting to the lateral reticular nucleus and the cerebellum.

Ascending projections of the cervical spinal cord neurones to the lateral reticular nucleus (LRN) and the restiform body (RB) were electrophysiologically investigated in alpha-chloralose anaesthetized cats. The main purpose of the study was to demonstrate whether the some of C6/C7 segments neurones gave off collateral branches that reached both the LRN and RB. Antidromic action potentials were recorded from 50 neurones located in laminae IVVIII of the grey matter of C6/C7 segments following stimulation of the LRN and RB with tungsten electrodes. Analysis of the antidromic responses allowed to distinguish three populations of neurones according to their projection patterns, 41% cells ascended exclusively to either one of the two structures investigated (26% to LRN and 15% to RB), while in the remaining cases (59%) collateral projections ascended to both LRN and RB. The axonal conduction velocities were comprised in the range of 14-90 m/s and no differences were found when compared mean values for particular groups of neurones. In conclusion, the results obtained indicate that in a great number of C6/C7 neurones both spinoreticular and spinocerebellar projections are present. It is likely that afferent input from forelimbs may be directly of indirectly transmitted to the cerebellum through the same neurones.

Projection to the lateral reticular nucleus from neurons located in C6-C7 segments of the spinal cord. An electrophysiological study in the cat.

Spinoreticular neurons projecting to the lateral reticular nucleus (LRN) were investigated electrophysiologically in the cervical enlargement of the cat spinal cord. Experiments were performed on alpha-chloralose anaesthetized animals. Antidromic action potentials were recorded extracellularly from cells located in C6 and C7 segments following stimulation of the ipsilateral LRN. The total sample included 50 neurons. Their cell bodies were found to be distributed in Rexed's laminae VI-VIII of the gray matter. Axonal conduction velocities ranged from 14.7 to 89.7 ms-1. Considerable differences between particular cases enabled two separate groups of slower and faster conduction to be distinguished. Values for these two groups were 14.7-44.3 ms-1 and 52.2-89.7 ms-1, respectively. Discrete differences with regard to the location of these groups were also pointed out. Such differentiation suggests that a proportion of axons from the slower conducting pool may be in fact collaterals of neurons that project to other brainstem centers or to lower levels of the spinal cord.