Overexpression of kynurenic acid in stroke: An endogenous neuroprotector?

It is known that kynurenic acid (KYNA) exerts a neuroprotective effect against the neuronal loss induced by ischemia; acting as a scavenger, and exerting antioxidant action. In order to study the distribution of KYNA, a highly specific monoclonal antibody directed against KYNA was developed. This distribution was studied in control rats and in animals in which a middle cerebral artery occlusion (stroke model) was induced. By double immunohistochemistry, astrocytes containing KYNA and GFAP were exclusively found in the ipsilateral cerebral cortex and/or striatum, at 2, 5 and 21days after the induction of stroke. In control animals and in the contralateral side of the stroke animals, no immunoreactivity for KYNA was found. Under pathological conditions, the presence of KYNA is reported for the first time in the mammalian brain from early phases of stroke. The distribution of KYNA matches perfectly with the infarcted regions suggesting that, in stroke, this overexpressed molecule could be involved in neuroprotective/scavenger/antioxidant mechanisms.

Randomized controlled trial comparing the effectiveness of the ultrasound-guided galvanic electrolysis technique (USGET) versus conventional electro-physiotherapeutic treatment on patellar tendinopathy.

BACKGROUND: Patellar tendinopathy has a high prevalence rate among athletes. Different therapeutic options can be found in the current literature, but none of them has been clearly established as the gold standard. The purpose of this study is to compare, in a randomized controlled trial, the clinical efficacy of eccentric exercise combined with either an ultrasound-guided galvanic electrolysis technique (USGET) or conventional electrophysiotherapy to treat patellar tendinopathy. METHODS: Sixty patients diagnosed with patellar tendinopathy were randomized into two groups. Group 1 (n = 30) received electrophysiotherapy treatment consisting of ultrasound, laser and interferential current techniques. Group 2 (n = 30) received USGET. Both groups did the same standardized eccentric exercise program. Periodic assessments of the subjects were carried out with the Victorian Institute of Sport Assessment-Patella (VISA-P) score. An analysis of means and a survival study were performed. RESULTS: There were statistically significant differences in the VISA-P between the baseline and final follow-up in each treatment group. Group 1 (conventional electrophysiotherapy) went from 52.5 ± 18.8 to 61.9 ± 13.7 (in VISA-P < 90 subgroup) and from 69.1 ± 9.1 to 95.2 ± 2.5 (in VISA-P > 90 subgroup). Group 2 (USGET) went from 51.4 ± 17.9 to 63.3 ± 14.3 (in VISA-P < 90 subgroup) and from 66.3 ± 13.1 to 97.1 ± 1.7 (in VISA-P > 90 subgroup). There were statistically significant correlations between the baseline and final score in the VISA-P > 90 subjects upon completing the study but no statistically significant correlations between subjects with VISA-P < 90. The mean number of sessions applied was 22.6 ± 2.5 in Group 1 and 3.2 ± 0.9 in Group 2. The success probability in Group 1 was 36.1% versus 72.4% in Group 2. The difference was statistically significant. CONCLUSION: The results obtained with the combination of USGET and eccentric exercise reported better outcomes than with the conventional electrophysiotherapy techniques in the treatment of patellar tendinopathy.

NO-tryptophan: a new small molecule located in the rat brain.

A highly specific monoclonal antibody directed against nitric oxide-tryptophan (NO-W) with good affinity (10-9 M) and specificity was developed. In the rat brain, using an indirect immunoperoxidase technique, cell bodies containing NO-W were exclusively found in the intermediate and dorsal parts of the lateral septal nucleus. No immunoreactive fibres were found in the rat brain. This work reports the first visualization and the morphological characteristics of cell bodies containing NO-W in the mammalian brain. The restricted distribution of NO-W in the rat brain suggests that this molecule could be involved in specific physiological mechanisms.

3-hydroxi-anthranilic acid is early expressed in stroke.

Using an immunohistochemical technique, we have studied the distribution of 3-OH-anthranilic acid (3-HAA) in the rat brain. Our study was carried out in control animals and in rats in which a stroke model (single transient middle cerebral artery occlusion) was performed. A monoclonal antibody directed against 3-HAA was also developed. 3-HAA was exclusively observed in the infarcted regions (ipsilateral striatum/cerebral cortex), 2, 5 and 21 days after the induction of stroke. In control rats and in the contralateral side of the stroke animals, no immunoreactivity for 3-HAA was visualized. Under pathological conditions (from early phases of stroke), we reported for the first time the presence of 3-HAA in the mammalian brain. By double immunohistochemistry, the coexistence of 3-HAA and GFAP was observed in astrocytes. The distribution of 3-HAA matched perfectly with the infarcted regions. Our findings suggest that, in stroke, 3-HAA could be involved in the tissue damage observed in the infarcted regions, since it is well known that 3-HAA exerts cytotoxic effects.

Early growth hormone (GH) treatment promotes relevant motor functional improvement after severe frontal cortex lesion in adult rats.

A number of studies, in animals and humans, describe the positive effects of the growth hormone (GH) treatment combined with rehabilitation on brain reparation after brain injury. We examined the effect of GH treatment and rehabilitation in adult rats with severe frontal motor cortex ablation. Thirty-five male rats were trained in the paw-reaching-for-food task and the preferred forelimb was recorded. Under anesthesia, the motor cortex contralateral to the preferred forelimb was aspirated or sham-operated. Animals were then treated with GH (0.15 mg/kg/day, s.c) or vehicle during 5 days, commencing immediately or 6 days post-lesion. Rehabilitation was applied at short- and long-term after GH treatment. Behavioral data were analized by ANOVA following Bonferroni post hoc test. After sacrifice, immunohistochemical detection of glial fibrillary acid protein (GFAP) and nestin were undertaken in the brain of all groups. Animal group treated with GH immediately after the lesion, but not any other group, showed a significant improvement of the motor impairment induced by the motor lesion, and their performances in the motor test were no different from sham-operated controls. GFAP immunolabeling and nestin immunoreactivity were observed in the perilesional area in all injured animals; nestin immunoreactivity was higher in GH-treated injured rats (mainly in animals GH-treated 6 days post-lesion). GFAP immunoreactivity was similar among injured rats. Interestingly, nestin re-expression was detected in the contralateral undamaged motor cortex only in GH-treated injured rats, being higher in animals GH-treated immediately after the lesion than in animals GH-treated 6 days post-lesion. Early GH treatment induces significant recovery of the motor impairment produced by frontal cortical ablation. GH effects include increased neurogenesis for reparation (perilesional area) and for increased brain plasticity (contralateral motor area).

Direct visualization of retinoic acid in the rat hypothalamus: an immunohistochemical study.

In order to increase our knowledge about the distribution of vitamins in the mammalian brain, we have developed a highly specific antiserum directed against retinoic acid with good affinity (10(-8) M), as evaluated by ELISA tests. In the rat brain, no immunoreactive fibers containing retinoic acid were detected. Cell bodies containing retinoic acid were only found in the hypothalamus. This work reports the first visualization and the morphological characteristics of cell bodies containing retinoic acid in the mammalian paraventricular hypothalamic nucleus and in the dorsal perifornical region, using an indirect immunoperoxidase technique. The restricted distribution of retinoic acid in the rat brain suggests that this vitamin could be involved in very specific physiological mechanisms.

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.

Immunocytochemical visualization of D-glutamate in the rat brain.

Using highly specific antisera directed against conjugated d-amino acids, the distribution of d-glutamate-, d-tryptophan-, d-cysteine-, d-tyrosine- and d-methionine-immunoreactive structures in the rat brain was studied. Cell bodies containing d-glutamate, but not d-glutamate-immunoreactive fibers, were found. Perikarya containing this d-amino acid were only found in the mesencephalon and thalamus of the rat CNS. Thus, the highest density of cell bodies containing d-glutamate was observed in the dorsal raphe nucleus, the ventral part of the mesencephalic central gray, the superior colliculus, above the posterior commissure, and in the subparafascicular thalamic nucleus. A moderate density of immunoreactive cell bodies was observed in the dorsal part of the mesencephalic central gray, above the rostral linear nucleus of the raphe, the nucleus of Darkschewitsch, and in the medial habenular nucleus, whereas a low density was found below the medial forebrain bundle and in the posterior thalamic nuclear group. Moreover, no immunoreactive fibers or cell bodies were visualized containing d-tryptophan, d-cysteine, d-tyrosine or d-methionine in the rat brain. The distribution of d-glutamate-immunoreactive cell bodies in the rat brain suggests that this d-amino acid could be involved in several physiological mechanisms. This work reports the first visualization and the morphological characteristics of conjugated d-glutamate-immunoreactive cell bodies in the rat CNS using an indirect immunoperoxidase technique. Our results suggest that the immunoreactive neurons observed have an uptake mechanism for d-glutamate.

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.

[Implication of the neuropeptides methionine enkephalin, neurotensin and somatostatin of the caudal trigeminal nucleus in the experimental migraine]. / Implicación de los neuropéptidos metionina-encefalina, neurotensina y somatostatina del núcleo caudal del trigémino en la migraña experimental.

INTRODUCTION: Primary peptidergic sensory neurons of the trigeminal ganglion that innervate the cerebral dura have been involved in the pathogenesis of headache, including the migraine. In addition, it is known that nociceptive central processes of the trigeminal neurons terminate in the caudal trigeminal nucleus. Moreover, the electrical stimulation of the trigeminal ganglion has been used as an experimental model in order to study the vascular headache, including the migraine. AIM: To study whether there is or not a decrease of the immunoreactivity for methionine enkephalin, somatostatin and neurotensin in the caudal trigeminal nucleus after electrical stimulation of the trigeminal ganglion. MATERIAL AND METHODS: The trigeminal ganglia of Wistar albino rats of both sexes were electrically stimulated (frequency, 5 Hz; duration, 5 ms; intensity, 0,8 1.4 mA) and unilaterally for five minutes. Sections of the medulla oblongata containing the caudal trigeminal nucleus were obtained and processed for immunocytochemistry, in which specific antibodies were used against methionine enkephalin, neurotensin and somatostatin 28. RESULTS: In stimulated animals, we observed a decrease in the immunoreactivity for the three neuropeptides studied in the stimulated (ipsilateral) side, in comparison with the not stimulated side (contralateral). In control animals (not stimulated) the degree of the immunoreactivity was the same on both sides. CONCLUSIONS: 1. The decrease of the immunoreactivity in the ipsilateral side (stimulated) suggests that methionine enkephalin, neurotensin and somatostatin 28 are released in the caudal trigeminal nucleus after electrical stimulation of the trigeminal ganglion; 2. Methionine enkephalin and somatostatin 28 could act in the caudal trigeminal nucleus as inhibitors (with antinociceptive action) of another released exciters neuropeptides (with nociceptive action); and 3. These data will allow in the future to try new therapeutic strategies (e.g., the inhibition of the receptors implicated.), in order to alleviate certain headaches.

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.

Depletion of substance P, neurokinin A and calcitonin gene-related peptide from the contralateral and ipsilateral caudal trigeminal nucleus following unilateral electrical stimulation of the trigeminal ganglion; a possible neurophysiological and neuroanatomical link to generalized head pain.

Primary trigeminal neurons of the trigeminal ganglion (TG) innervate major parts of the face and head, including the dura. Electrical stimulation of the TG at specific parameters, can activate its nociceptive neurons and may serve as an experimental pain model. Markowitz [J. Neurosci. 7 (1987) 4129] reported that electrical stimulation of the trigeminal ganglion (TG) causes extravasation of plasma proteins from venules of the trigeminally innervated domain possibly due to the release of vasoactive substances. Neurogenic inflammation (vasodilatation, plasma protein extravasation, release of vasoactive peptides) in dura may serve as one of the possible pathomechanisms underlying vascular head pain [Moskowitz, Ann. Neurol. 16 (1984) 157]. We performed a unilateral electrical stimulation (7.5 Hz, 5 ms, 0.8-1.4 mA for 5 min) of the TG in rat, to induce a neurogenic inflammation in the peripheral trigeminal domain including the dura, looking for calcitonin gene related peptide (CGRP), substance P (SP) and neurokinin A (NKA) immunoreactivity (IR) in the caudal trigeminal nucleus (CTN) into which massive central trigeminal processes terminate. Here, we show patchy depletion(s) of CGRP-, SP- and NKA-IRs in the contralateral CTN of the rat in addition to their ipsilateral depletion. Such depletion is due to the release of these neuropeptides in the CTN leading to the activation of bilateral trigeminal nociceptive pathway. These data afford the possibility that under specific frequencies (which may roughly correlate to the intensity of the painful stimulus) and/or specific intensities (may correlate to specific areas of the peripheral trigeminal domain) of stimulation, activation of one side of the TG may activate bilateral trigeminal nociceptive pathway leading to the perception of an ill localized/generalized pain or headache rather than a unilateral one.

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.

Simultaneous depletion of neurokinin A, substance P and calcitonin gene-related peptide from the caudal trigeminal nucleus of the rat during electrical stimulation of the trigeminal ganglion.

The central terminals of the primary sensory trigeminal ganglion (TG) neurons projecting into the caudal trigeminal nucleus (CTN) of the rat exhibit neurokinin A (NKA)-, substance P (SP)-, and calcitonin gene-related peptide (CGRP)-immunoreactivities (IRs). We stimulated the TG in the rat to induce some of the alterations which might occur during migraine (neurogenic inflammation). Under a stereotaxic apparatus and by means of a bipolar electrode, one-side TG of the animals were electrically stimulated (7.5 Hz, 5 ms, 0.8-1. 4 mA) with square pulses for 5 min. Then, using immunohistochemical methods, the lower medulla of each rat was studied for NKA-, SP- and CGRP-IRs. Light microscopic examination of brain-stem sequencial sections revealed a simultaneous decrease in the immunoreactivities of all neuropeptides (NKA, SP and CGRP) in the CTN ipsilateral to TG stimulation in comparison with the other (not stimulated) side CTN. It is suggested that this decrease in immunoreactivity would be due to the co-release of neuropeptides following noxious stimuli and that NKA, SP and CGRP might therefore act as co-transmitters or co-modulators at the first central synapses of the trigeminal sensory pathway.

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.

Alterations in neurokinin A-, substance P- and calcitonin gene-related peptide immunoreactivities in the caudal trigeminal nucleus of the rat following electrical stimulation of the trigeminal ganglion.

We have carried out an immunohistochemical study on the presence of neurokinin A (NKA) and substance P (SP) in the rat caudal trigeminal nucleus (CTN) after electrical stimulation of the trigeminal ganglion (TG), used as an experimental model to induce alterations, some of which may occur during migraine attacks (release of vasoactive peptides from perivascular trigeminal axons and neurogenic inflammation). Both unilateral, 30 min electrical stimulation (5 Hz, 5 ms, 0.1-1 mA) of the TG and 5 min stimulation with a slight increase in the stimulating parameters (7.5 Hz, 5 ms, 1.4 mA) caused a significant depletion of the NKA and SP immunoreactivities (-IR) of the TG nerve central terminals in the ipsilateral CTN. Calcitonin gene-related peptide (CGRP)-IR of the ipsilateral CTN was also studied in the CTN using the increased stimulating parameters and a marked depletion of CGRP-IR was also observed following TG stimulation. Such depletion may be due to the release of neuropeptides from the trigeminal central terminals. These findings suggest that NKA, SP and CGRP could act as neurotransmitters at the first central synapses of the trigeminal nociceptive pathway to transmit the sensory stimuli to the higher brain centers.

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.

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.