El trasplante de astrocitos encapsulados mejoran el déficit motor en la habilidad manual producido por la lesión de la corteza frontal en ratas adultas / Transplant of encapsulated astrocyte ameliorate lesion-induced motor deficits in adults rats with frontal cortex injury

Objetivo: Investigar la capacidad de trasplantes de astrocitos encapsulados en esferas de alginato de recuperar el déficit en la habilidad manual producida por la lesión de la corteza frontal, en ratas adultas. Material y metodología: Se utilizaron ratas Wistar, y se emplearon pruebas conductuales, cultivos celulares, técnica de encapsulación de células y trasplantes. Los animales se condicionaron en un test de habilidad motora fina y se determinó su mano preferente. Se lesionó la corteza frontal contralateral a la mano preferente y se evaluó la efectividad de la lesión mediante el test de conducta. En un grupo de animales lesionados se trasplantó astrocitos encapsulados en esferas de alginato en la cavidad producida por la lesión; en un segundo grupo, se trasplantó tejido cortical fetal; y en un tercer grupo, se implantó esferas de alginato sin células. Resultados: A los tres meses post-trasplante, tanto los animales con trasplantes de astrocitos encapsulados como con trasplantes de tejido cortical mejoraron el déficit motor inducido por la lesión. Los animales con trasplantes de esferas de alginato vacías no experimentaron mejoría. Conclusión: Los trasplantes de astrocitos encapsulados mejoran, a largo plazo, el deficit motor. El alginato indujo efectos secundarios en el huésped (AU)

Objetive: To investigate whether transplants of encapsulated astrocytes in alginate spheres were able to recover the deficit in motor skills produced by frontal cortex lesion, in adult rats. Material and method: Male Wistar rats were used. Behavioral test, tissue culture, astrocyte transplants and immunocytochemical and histological techniques were applied. Animals were conditioned in a paw reaching for food task and the preferred paw determine. Lesion was produced in the frontal cortex contralateral to the preferred paw and the effectiveness of the lesion tested. In one group of lesion animals, encapsulated astrocytes in alginate spheres were implanted in the lesion cavity; in a second group, fetal cortical tissue was used as donor material; while in a third group empty alginate spheres were implanted. Results: Three months after grafting, the rats with encapsulated astrocyte or with fetal cortical tissue transplants ameliorated the lesion-induced motor deficit.The rats with implant of empty alginate spheres showed no improvement. Conclusion: Transplants of encapsulated astrocytes in alginate spheres induce a long- term improvement of motor lesion deficits. The alginate induced long-term side effects on the host (AU)

Recuperación de la habilidad motora mediante trasplantes neurales en ratas adultas con lesión de la corteza frontal / Motor skill recovery through neural transplants in adult rats with frontal cortex damage

Objetivo: Investigar los mecanismos involucrados en la recuperación funcional de alteraciones motoras producidas por la lesión de la corteza frontal mediante trasplantes neurales embrionarios, en ratas adultas. Material y metodología: Utilizamos ratas machos, de raza Wistar, empleando pruebas conductuales, métodos electrofisiológicos y técnicas inmunohistoquímicas e histológicas. Los animales se condicionaron en un test motor específico de habilidad motora fina y se determinó su mano preferente. Se realizó una lesión en la corteza frontal contralateral a la mano preferente y se evaluó la efectividad de la lesión mediante el test de conducta. En un grupo de animales lesionados se trasplantó tejido cortical embrionario en la cavidad producida por la lesión; en un segundo grupo, se utilizó tejido fetal amigdalino como tejido donante; y en un tercer grupo, se trasplantó nervio ciático de rata adulta. Los tres grupos se compararon con un grupo de animales control. Resultados: A los tres meses post-trasplante, los animales con trasplantes de tejido fetal amigdalino y con trasplantes de tejido cortical mejoraron el déficit motor producido por la lesión. Los animales con trasplantes de nervio ciático no presentaron ninguna mejoría. Conclusión: Los trasplantes de tejido amigdalino inducen una mejoría similar a la obtenida con los trasplantes de tejido cortical. El origen ontogenético, en parte común, del tejido amigdalino y el tejido cortical podría estar implicado en los mecanismos subyacentes a la recuperación funcional (AU)

Objetive: To investigate the mechanisms by which neural transplants contribute to functional recovery of the motor disorders produced by frontal cortex damage in adult rats. Material and methods: Male Wistar rats were used, with the application of behavioral tests, electrophysiological methods and immunohistochemical and histological techniques. The animals were conditioned using a specific fine motor skill test, with determination of the dominant paw. Damage was produced in the frontal cortex contralateral to the dominant paw, with evaluation of the effectiveness of the lesion based on the behavioral test. In one group of damaged animals embryonic cortical tissue was implanted in the cavity left by the lesion. In a second group fetal amygdaline tissue was used as donor material, while in a third group adult rat sciatic nerve was implanted. The three groups were compared with a control group. Results: Three months after grafting, the rats with fetal amygdaline tissue and with transplanted cortical material improved of the motor defect induced by the lesion. The rats with grafted sciatic nerve showed no improvement. Conclusion: Amygdaline tissue grafts induce improvement similar to that recorded with cortical tissue transplants. The partially shared ontogenetic origin of amygdaline and cortical tissue could be implicated in the functional recovery mechanisms (AU)

Single-cell recordings: a method for investigating the brain's activation pattern during exercise.

The precision of human movements to generate skills as accurate as the exercises performed by athletes are the consequence of a long and complex learning process. These processes involve a great amount of the nervous system's structures. Electrophysiological techniques have been largely used to highlight brain functions related to the control of these kinds of movements. These methods cover invasive and non-invasive techniques which have been applied to humans and experimental animals. We describe here electrophysiological techniques that are used in behaving animals. Especially, we will focus on the analysis and results obtained from single-cell recording in the prefrontal cortex to explain the relationship between single neuronal activity and movement during locomotion. In addition, we will show how, analyzing these results, that we can characterize the integrative role of neurons involved in the control of locomotion. The objective is to demonstrate single-cell recording techniques as suitable methods to study, in experimental animals, the brain's activation pattern during exercise.

Long-term effects of electroconvulsive therapy on episodic memory.

INTRODUCTION: Current guidelines consider electroconvulsive therapy (ECT) as a treatment of choice for some depressive disorders; however some psychiatrists are still reluctant toward using ECT as first choice treatment. This fact is probably due to its short-term deleterious effects on memory and cognition. OBJECTIVE: To investigate long-term effects of ECT on anterograde episodic memory. METHODS: Participants were assigned to three groups: 20 major depression patients receiving ECT treatment (group A), 28 major depression patients following only pharmacological therapy (group B) and 26 healthy controls (group C). Group A patients received three ECT sessions. Memory evaluation consisted of three tests: list of words, and logical memory I and II. Memory evaluation was performed before treatment (baseline) and six months post-treatment. RESULTS: Groups A and B performed at a similar level in baseline evaluation. Post-treatment evaluation indicated that ECT was associated with a significantly better clinical situation and improvement in all memory tests. There was also a very strong correlation between clinical improvement and memory performance. CONCLUSIONS: According to our results, ECT was not associated with deleterious effects on anterograde episodic memory. ECT produced faster and significantly higher clinical improvement, as measured by means of Hamilton Depression Rating Scale, which also correlates with memory performance.

Efectos a largo plazo de la terapia electroconvulsiva sobre la memoria episódica / Long-term effects of electroconvulsive therapy on episodic memory

Introducción. Los criterios actuales consideran la terapia electroconvulsiva (TEC) como un tratamiento de elección para ciertos trastornos depresivos; sin embargo, algunos psiquiatras son aún reticentes a su utilización. Este hecho se debe probablemente a sus efectos deletéreos a corto plazo sobre la memoria y la cognición. Objetivo. Evaluar los efectos a largo plazo de la TEC sobre la memoria anterógrada episódica. Métodos. Tres grupos participaron en el estudio: 20 pacientes con depresión mayor tratados con TEC (grupo A), 28 pacientes con depresión mayor que se mantienen exclusivamente con el tratamiento farmacológico (grupo B) y 26 sujetos control (grupo C). Los pacientes del grupo A recibieron tres sesiones de TEC. Las pruebas para la evaluación de la memoria fueron: recuerdo de una lista de palabras y memoria lógica I y II. La evaluación de la memoria se realizó antes del inicio del tratamiento (línea de base) y 6 meses postratamiento. Resultados. Los grupos A y B mostraron unos niveles de ejecución similares en línea de base. La evaluación postratamiento indicó que la TEC está asociada con una situación clínica significativamente mejor y puntuaciones superiores en todas las pruebas de memoria. Además existe una correlación muy fuerte entre la mejoría clínica y la ejecución en la pruebas de memoria. Conclusiones. De acuerdo con nuestros resultados la TEC no está asociada con efectos deletéreos sobre la memoria anterógrada episódica. La TEC produjo una mejoría clínica más rápida y más importante, medida según la Escala de Hamilton para la Depresión, que además se correlaciona con la ejecución en las pruebas de memoria

Introduction. Current guidelines consider electroconvulsive therapy (ECT) as a treatment of choice for some depressive disorders; however some psychiatrists are still reluctant toward using ECT as first choice treatment. This fact is probably due to its short-term deleterious effects on memory and cognition. Objective. To investigate long-term effects of ECT on anterograde episodic memory. Methods. Participants were assigned to three groups: 20 major depression patients receiving ECT treatment (group A), 28 major depression patients following only pharmacological therapy (group B) and 26 healthy controls (group C). Group A patients received three ECT sessions. Memory evaluation consisted of three tests: list of words, and logical memory I and II. Memory evaluation was performed before treatment (baseline) and six months post-treatment. Results. Groups A and B performed at a similar level in baseline evaluation. Post-treatment evaluation indicated that ECT was associated with a significantly better clinical situation and improvement in all memory tests. There was also a very strong correlation between clinical improvement and memory performance. Conclusions. According to our results, ECT was not associated with deleterious effects on anterograde episodic memory. ECT produced faster and significantly higher clinical improvement, as measured by means of Hamilton Depression Rating Scale, which also correlates with memory performance

Combined kinetic analysis of solid-state reactions: a powerful tool for the simultaneous determination of kinetic parameters and the kinetic model without previous assumptions on the reaction mechanism.

The combined kinetic analysis implies a simultaneous analysis of experimental data representative of the forward solid-state reaction obtained under any experimental conditions. The analysis is based on the fact that when a solid-state reaction is described by a single activation energy, preexponetial factor and kinetic model, every experimental T-alpha-dalpha/dt triplet should fit the general differential equation independently of the experimental conditions used for recording such a triplet. Thus, only the correct kinetic model would fit all of the experimental data yielding a unique activation energy and preexponential factor. Nevertheless, a limitation of the method should be considered; thus, the proposed solid-state kinetic models have been derived by supposing ideal conditions, such as unique particle size and morphology. In real systems, deviations from such ideal conditions are expected, and therefore, experimental data might deviate from ideal equations. In this paper, we propose a modification in the combined kinetic analysis by using an empirical equation that fits every f(alpha) of the ideal kinetic models most extensively used in the literature and even their deviations produced by particle size distributions or heterogeneities in particle morphologies. The procedure here proposed allows the combined kinetic analysis of data obtained under any experimental conditions without any previous assumption about the kinetic model followed by the reaction. The procedure has been verified with simulated and experimental data.

Beta-Amyloid peptide25-35 depresses excitatory synaptic transmission in the rat basolateral amygdala "in vitro".

The effects of beta-amyloid peptide25-35 on resting membrane potential, spontaneous and evoked action potential and synaptic activity have been studied in basolateral amygdaloid complex on slices obtained from adult rats. Intracellular recordings reveal that perfusion with beta-amyloid peptide25-35 at concentrations of 400 nM and less did not generate any effect on resting membrane potential. However, concentrations in the range of 800-1200 nM produced an unpredictable effect, depolarization and/or hyperpolarization, which were blocked by tetrodotoxin or 6-cyano-7-nitroquinoxaline-2,3-dione+D-(-)-2-amino-5-phosphonopentanoic acid together with bicuculline. Excitatory and inhibitory evoked responses mediated by glutamic acid or gamma-aminobutyric acid decreased in amplitude after beta-amyloid peptide25-35 perfusion. Additionally, results obtained using the paired-pulse protocol offer support for a presynaptic mode of action. To determine which type of receptors and/or channels are involved in the presynaptic mechanism of action, a specific blocker of alpha-7 nicotinic receptors (methyllycaconitine citrate) or L-type calcium channel blockers (calcicludine or nifedipine) were used. beta-amyloid petide25-35 decreased excitatory postsynaptic potentials amplitude in control conditions and also in slices permanently perfused with methyllycaconitine citrate. However, this effect was blocked in slices perfused with calcicludine or nifedipine suggesting the involvement of the L-type calcium channels. On the whole, these experiments provide evidence that beta-amyloid peptide25-35 affects neurotransmission in basolateral amygdala and its action is mediated through L-type calcium channels.

Low in vivo toxicity of a novel cisplatin-ursodeoxycholic derivative (Bamet-UD2) with enhanced cytostatic activity versus liver tumors.

Cisplatin-bile acid derivatives belonging to the Bamet-family maintain both liver organotropism and cytostatic activity. "In vivo" toxicity and usefulness as chemotherapeutic agent versus liver tumors of a novel drug, Bamet-UD2 [cis-diamminechlorocholylglycinate platinum (II)], with enhanced "in vitro" cytostatic activity was investigated. Using orthotopically implanted mouse Hepa 1-6 hepatoma in the liver of Nude mice, the antitumor effect of Bamet-UD2 was compared with that of a previously characterized compound of this family, Bamet-R2 [cis-diamminebis-ursodeoxycholate platinum(II)], and cisplatin. Life span was significantly prolonged in mice treated with both Bamets (Bamet-UD2 > Bamet-R2), compared with animals receiving saline or cisplatin. All these drugs inhibit tumor growth (Bamet-UD2 = cisplatin > Bamet-R2). However, toxicity-related deaths only occurred under cisplatin treatment. Using rats maintained in metabolic cages, organ-specific toxicity and drug accumulation in tissues were investigated. The amount of both Bamets in the liver was severalfold higher than that of cisplatin. By contrast, a significantly higher amount of cisplatin in kidney and nerve was found. In lung, heart, muscle, brain, and bone marrow the amount of drug was small and also significantly lower in animals receiving Bamets. Signs of neurotoxicity (altered nerve conduction velocity), nephrotoxicity (increased serum urea and creatinine concentrations and decreased creatinine clearance), and bone marrow toxicity (decreased platelet and white blood counts) in animals treated with cisplatin but not with the Bamets were found. These results indicate that, owing to strong antitumor activity together with absence of side effects, Bamet-UD2 may be useful in the treatment of liver tumors.

Functional recovery of skilled forelimb use in rats obliged to use the impaired limb after grafting of the frontal cortex lesion with homotopic fetal cortex.

The long-term effect of transplanting embryonic frontal cortex into a unilateral frontal cortex lesion has been studied in adult rats. Before surgery, activity in an open field, muscular strength of both forelimbs, and performance in a paw-reaching-for-food task were scored in 26 rats. In 21 animals a unilateral cortex lesion was then made in the forelimb motor area of the hemisphere contralateral to the preferred paw in the paw-reaching-for-food task, while the other 5 animals were sham-operated. On retesting, the lesion animals changed the preferred paw. A solid homotopic transplant of embryonic tissue (embryonic day 17) was then placed in the lesion cavity in 11 of the lesion rats. Three months later neither lesion alone nor lesion plus transplantation affected open field behavior and muscular strength, but the lesion permanently affected performance in the paw-reaching-for-food task, as shown by a change of preferred paw and a functional deficit in the paw contralateral to the lesion. Transplantation ameliorated the deficits caused by the lesion, but this was only evident when animals were forced to reach with the paw contralateral to the lesion plus transplant. The behavioral results were independent of the size of the lesion and graft. Connections between graft and host tissue were studied by means of the fluorescent tracer 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI). A dense array of labeled fibers was found in the host cortex adjacent to the transplant. The results suggest that functional recovery depends on grafting but is only evident when the animal is obliged to use the affected limb.

Muscarinic agonist carbachol depresses excitatory synaptic transmission in the rat basolateral amygdala in vitro.

Intracellular recordings in slice preparations of the basolateral amygdala were used to test which excitatory amino acid receptors mediate the excitatory postsynaptic potentials due to stimulation of the external capsule. These recordings were also used to examine the action of muscarinic agonists on the evoked excitatory potentials. Intracellular recordings from amygdaloid pyramidal neurons revealed that carbachol (2-20 microM) suppressed, in a dose-dependent manner, excitatory postsynaptic responses evoked by stimulation of the external capsule (EC). This effect was blocked by atropine. The estimated effective concentration to produce half-maximal response (EC(50)) was 6.2 microM. Synaptic suppression was observed with no changes in the input resistance of the recorded cells, suggesting a presynaptic mechanism. In addition, the results obtained using the paired-pulse protocol provided additional support for a presynaptic action of carbachol. To identify which subtype of cholinergic receptors were involved in the suppression of the EPSP, four partially selective muscarinic receptor antagonists were used at different concentrations: pirenzepine, a compound with a similar high affinity for muscarinic M1 and M4 receptors; gallamine, a noncompetitive antagonist for M2; methoctramine, an antagonist for M2 and M4; and 4-diphenylacetoxy-N-methylpiperidine, a compound with similar high affinity for muscarinic receptors M1 and M3. None of them independently antagonized the suppressive effect of carbachol on the evoked EPSP completely, suggesting that more than one muscarinic receptor subtype is involved in the effect. These experiments provide evidence that in the amygdala muscarinic agonists block the excitatory synaptic response, mediated by glutamic acid, by acting on several types of presynaptic receptors.

Rhythmic neuronal activity in the lateral cerebellum of the cat during visually guided stepping.

1. The discharge patterns of 117 lateral cerebellar neurones were studied in cats during visually guided stepping on a horizontal circular ladder. Ninety per cent of both nuclear cells (53/59) and Purkinje cells (53/58) showed step-related rhythmic modulations of their discharge frequency (one or more periods of 'raised activity' per step cycle of the ipsilateral forelimb). 2. For 31% of nuclear cells (18/59) and 34% of Purkinje cells (20/58) the difference between the highest and lowest discharge rates in different parts of the step cycle was > 50 impulses s-1. 3. Individual neurones differed widely in the phasing of their discharges relative to the step cycle. Nevertheless, for both Purkinje cells and nuclear cells population activity was significantly greater in swing than in stance; the difference was more marked for the nuclear population. 4. Some cells exhibited both step-related rhythmicity and visual responsiveness (28 of 67 tested, 42%), whilst others were rhythmically active during locomotion and increased their discharge rate ahead of saccadic eye movements (11 of 54 tested, 20%). The rhythmicity of cells that were visually responsive was typical of the rhythmicity seen in the whole locomotor-related population. The step-related rhythmicity of cells that also discharged in relation to saccades was generally below average strength compared with the cortical and nuclear populations as a whole. 5. The possibility is discussed that the rhythmicity of dentate neurones acts as a powerful source of excitatory locomotor drive to motor cortex, and may thereby contribute to establishing the step-related rhythmicity of motor cortical (including pyramidal tract) neurones. More generally, the activity patterns of lateral cerebellar neurones provide for a role in the production of visually guided, co-ordinated eye and body movements.

Muscarinic activation of a non-selective cationic conductance in pyramidal neurons in rat basolateral amygdala.

In the present study, a cationic membrane conductance activated by the acetylcholine agonist carbachol was characterized in vitro in neurons of the basolateral amygdala. Extracellular perfusion of the K+ channel blockers Ba2+ and Cs+ or loading of cells with cesium acetate did not affect the carbachol-induced depolarization. Similarly, superfusion with low-Ca2+ solution plus Ba2+ and intracellular EGTA did not affect the carbachol-induced depolarization, suggesting a Ca2+-independent mechanism. On the other hand, the carbachol-induced depolarization was highly sensitive to changes in extracellular K+ or Na+. When the K+ concentration in the perfusion medium was increased from 4.7 to 10 mM, the response to carbachol increased in amplitude. In contrast, lowering the extracellular Na+ concentration from 143.2 to 29 mM abolished the response in a reversible manner. Results of coapplication of carbachol and atropine, pirenzepine or gallamine indicate that the carbachol-induced depolarization was mediated by muscarinic cholinergic receptors, but not the muscarinic receptor subtypes M1, M2 or M4, specifically. These data indicate that, in addition to the previously described reduction of a time- and voltage-independent K+ current (IKleak), a voltage- and time-dependent K+ current (IM), a slow Ca2+-activated K+ current (sIahp) and the activation of a hyperpolarization-activated inward rectifier K+ current (IQ), carbachol activated a Ca2+-independent non-selective cationic conductance that was highly sensitive to extracellular K+ and Na+ concentrations.

Neuronal activity in the lateral cerebellum of the cat related to visual stimuli at rest, visually guided step modification, and saccadic eye movements.

1. The discharge patterns of 166 lateral cerebellar neurones were studied in cats at rest and during visually guided stepping on a horizontal circular ladder. A hundred and twelve cells were tested against one or both of two visual stimuli: a brief full-field flash of light delivered during eating or rest, and a rung which moved up as the cat approached. Forty-five cells (40%) gave a short latency response to one or both of these stimuli. These visually responsive neurones were found in hemispheral cortex (rather than paravermal) and the lateral cerebellar nucleus (rather than nucleus interpositus). 2. Thirty-seven cells (of 103 tested, 36%) responded to flash. The cortical visual response (mean onset latency 38 ms) was usually an increase in Purkinje cell discharge rate, of around 50 impulses s-1 and representing 1 or 2 additional spikes per trial (1.6 on average). The nuclear response to flash (mean onset latency 27 ms) was usually an increased discharge rate which was shorter lived and converted rapidly to a depression of discharge or return to control levels, so that there were on average only an additional 0.6 spikes per trial. A straightforward explanation of the difference between the cortical and nuclear response would be that the increased inhibitory Purkinje cell output cuts short the nuclear response. 3. A higher proportion of cells responded to rung movement, sixteen of twenty-five tested (64%). Again most responded with increased discharge, which had longer latency than the flash response (first change in dentate output ca 60 ms after start of movement) and longer duration. Peak frequency changes were twice the size of those in response to flash, at 100 impulses s-1 on average and additional spikes per trial were correspondingly 3-4 times higher. Both cortical and nuclear responses were context dependent, being larger when the rung moved when the cat was closer than further away. 4. A quarter of cells (20 of 84 tested, 24%) modulated their activity in advance of saccades, increasing their discharge rate. Four-fifths of these were non-reciprocally directionally selective. Saccade-related neurones were usually susceptible to other influences, i.e. their activity was not wholly explicable in terms of saccade parameters. 5. Substantial numbers of visually responsive neurones also discharged in relation to stepping movements while other visually responsive neurones discharged in advance of saccadic eye movements. And more than half the cells tested were active in relation both to eye movements and to stepping movements. These combinations of properties qualify even individual cerebellar neurones to participate in the co-ordination of visually guided eye and limb movements.

Cholinergic responses of morphologically and electrophysiologically characterized neurons of the basolateral complex in rat amygdala slices.

The electrophysiological properties, the response to cholinergic agonists and the morphological characteristics of neurons of the basolateral complex were investigated in rat amygdala slices. We have defined three types of cells according to the morphological characteristics and the response to depolarizing pulses. Sixty-six of the recorded cells (71%) responded with two to three action potentials, the second onwards having less amplitude and longer duration (burst). In a second group, consisting of 21 cells (22%), the response to depolarization was a train of spikes, all with the same amplitude (multiple spike). Finally, seven neurons (7%) showed a single action potential (single spike). Burst response and multiple-spike neurons respond to the cholinergic agonist carbachol (10-20 microM) with a depolarization that usually attained the level of firing. This effect was accompanied by decreased or unchanged input membrane resistance and was blocked by atropine (1.5 microM). The depolarizing response to superfusion with carbachol occurred even when synaptic transmission was blocked by tetrodotoxin, indicating a direct effect of carbachol. Similarly, the depolarization by carbachol was still present when the M-type conductance was blocked by 2 mM Ba2+. The carbachol-induced depolarization was prevented by superfusion with tetraethylammonium (5 mM). Injection of biocytin into some of the recorded cells and subsequent morphological reconstruction showed that "burst" cells have piriform or oval cell bodies with four or five main dendritic trunks; spines are sparse or absent on primary dendrites but abundant on secondary and tertiary dendrites. This cellular type corresponds to a pyramidal morphology. The "multiple-spike" neurons have oval or fusiform somata with four or five thick primary dendritic trunks that leave the soma in opposite directions; they have spiny secondary and tertiary dendrites. Finally, neurons which discharge with a "single spike" to depolarizing pulses are round with four or five densely spiny dendrites, affording these neurons a mossy appearance. The results indicate that most of the amygdaloid neurons respond to carbachol with a depolarization. This effect was concomitant with either decrease or no change in the membrane input resistance and was not blocked by the addition of Ba2+, an M-current blocker, indicating that a conductance pathway other than K+ is involved in the response to carbachol.

Electrophysiological study of prefrontal neurones of cats during a motor task.

The prefrontal cortex is involved in many processes, some of which are related to motor activity such eye movements and speech. Experimental data exist that suggest that prefrontal cortical activity occurs in relation to attention, short-term memory, affective discrimination, and complex forms of motor behaviour, i.e. anticipatory preparation, motor sequences, programming of speech, etc. We were interested in studying participation of this cortical region in locomotion. For this purpose, recordings were made of unitary activity in the prefrontal cortex of chronically prepared cats walking on an exercise belt that was moving at a speed of 0.1 m/s. From a total of 63 neurones in the prefrontal area from which recordings were made, 37 (59%) changed their activity during locomotion, 28 of which (76%) increased and 9 of which (24%) decreased their frequency of discharge; the remaining 26 units (41%) showed no locomotor-related change in activity. The results obtained show that 59% of prefrontal units are involved in the locomotor process and it is reasonable to assume that their activity contributes to the control of the movements.

Changes in the discharge patterns of cat motor cortex neurones during unexpected perturbations of on-going locomotion.

1. The impulse activity of single neurones in the forelimb part of the motor cortex was recorded extracellularly in unrestrained cats during self-paced locomotion on a horizontal circular ladder. 2. Fifty-one cells (forty-nine of which discharged rhythmically in time with the step cycle) were recorded during encounters with a number of rungs that could be locked firmly in position or, alternatively, held in position by weak springs so that when stepped on they unexpectedly descended (under the weight of the animal) from 1 to 5 cm before contacting a mechanical stop. 3. In eleven cells (22%) including four fast-axon pyramidal tract neurones (PTNs), an increase in discharge occurred when the contralateral forelimb descended unexpectedly. Onset latency relative to the start of rung movement ranged from ca 20 to ca 100 ms. In eight cells latency was such that most of the response preceded contact of the rung with the stop; averaged over a number of trials the altered discharge in five of these cells (including two PTNs) represented an accurate profile of the averaged velocity of rung (and foot) descent. The three remaining cells appeared to be responding largely to the cessation of rung movement. 4. Thirty-six of the cells were also studied during unexpected descent of the ipsilateral forelimb and six (17%) displayed an increase in discharge (onset latency ca 35 to ca 80 ms); three of these were among those that also responded to contralateral descents. 5. These findings for skilled locomotion requiring a high degree of visuomotor coordination are discussed and it is concluded that the motor cortex is rapidly informed regarding unexpected perturbations delivered to the contralateral forelimb at the onset of stance and that changes are evoked in the pattern of impulse traffic descending via the pyramidal tract.

Electrophysiological influences of the parietal cortex and dorso-medial thalamic nucleus on the prefrontal cortex of the cat.

Lesion studies have shown that the functional integrity of prefrontal and posterior parietal cortex is necessary for complex behavioural performance. Recordings were made from 137 prefrontal cells in awake cats. Parietal cortex stimulation affected fifty-four cells (39.5%); thirty-four (63%) increased and twenty (37%) decreased their discharge frequency. Thalamic stimulation affected forty-seven cells; twenty-eight increased their discharge and nineteen decreased it. These responses suggest firstly that the organization between parietal and prefrontal cortex is similar to that in monkeys, and secondly that prefrontal cortex has an integrative role.

Passive avoidance conditioning and unitary activity in the basolateral amygdaloid nucleus of the rat.

Single unit activity was recorded in the basolateral nucleus of amygdala in rats in a passive avoidance test. Simultaneously, visual control of exploratory behaviour was carried out. Prior to establishing the conditioning, the mean frequency of the unit discharge was 14 Hz (SD = 9) and 1 minute after conditioning this unit activity decreased to values close to zero; later on (24 and 48 hours), a progressive recovery of the discharge was observed. Behavioural changes were also detected. The long term recovery of unit activity follows the time course of the extinction process. The possible significance of these findings is discussed in relation to some of the functional roles of this nucleus.