Biomedical subjects

C Bucherelli

Publications and source records attributed to C Bucherelli.

At least 37 records · Page 2Linked to original sources

PubMed1996

Amnesic effects of preacquisition, postacquisition, or preretrieval tetrodotoxin administration into the medial septal area on rat's passive avoidance memorization.

By means of local administration of tetrodotoxin (TTX) fully reversible functional inactivation of the medial septal area (MSA) of the rat was obtained in order to define the role of this structure in the retention of a conditioned passive avoidance response (PAR). In permanently cannulated animals, TTX (5 ng in 0.5 microl saline) or saline (0.5 microl) was injected in the MSA. TTX or saline was administered to six different groups of rats, respectively 1 h before PAR acquisition, immediately after PAR acquisition, and 1 h before PAR retrieval, performed 48 h after the acquisition trial. It was shown that MSA preacquisition and preretrieval TTX injections were followed by significant PAR retention impairment, while postacquisition TTX administration had no effect on PAR retention. The results indicate a well-defined mnemonic role of MSA during the acquisition and retrieval periods but not during the consolidation of PAR engram. The experimental evidence is discussed in relation to other reports and to MSA connectivity with other subcortical structures.

Animals↗

PubMed1995

Time-dependent deficits of rat's memory consolidation induced by tetrodotoxin injections into the caudate-putamen, nucleus accumbens, and globus pallidus.

In order to better define corpus striatum involvement in memory processing, tetrodotoxin functional ablation was employed to assess the respective roles of the caudate-putamen as a whole and of its anterior, median, and posterior regions, of the nucleus accumbens, and of the globus pallidus during early passive avoidance response consolidation of the rat. Under general ketamine anesthesia (100 mg/kg) by means of microinjections, tetrodotoxin (10 ng/microliter) was bilaterally administered at the appropriate stereotaxic locations of the chosen sites and subsites at different postacquisition delays (0.25, 1.5, and 6 h). Saline solution was administered to control subjects in the same sites. Rats always underwent retrieval testing 48 h after treatment, i.e., when tetrodotoxin blockade had completely disappeared. The results show that both total caudate-putamen and median caudate-putamen blockades caused passive avoidance responding impairment when performed at 0.25- and 1.5-h postacquisition delays, that caudate-putamen anterior and caudate-putamen posterior blockades were never followed by passive avoidance impairment, and that both nucleus accumbens and globus pallidus blockades were followed by passive avoidance impairment when performed at 0.25- and 1.5-h postacquisition delays. In all structures, tetrodotoxin administration caused no impairment at the 6-h delay. The results are discussed with reference both to previous results obtained after reversible or irreversible lesions of the same structures and to the functional mnemonic relationships of the corpus striatum and its components with other subcortical structures, particularly the substantia nigra.

Animals↗

PubMed1995

Transitory effects of intracerebral administration of protein synthesis inhibitors on rat's spontaneous behavior.

In order to evaluate whether the effects of the local administration of protein synthesis inhibitors are transient or permanent, small volumes of cycloheximide, 2-deoxy-d-galactose, tetrodotoxin, and saline solution were stereotaxically administered in the amygdala, substantia nigra, and nucleus basalis magnocellularis of naive male adult Wistar rats. Three spontaneous activities (feeding, drinking, locomotion) were continuously recorded. 12 groups of animals were housed in activity cages for 6 consecutive days with a light/dark schedule (LD 12:12). The active compounds at doses sufficient to cause only limited effects were administered at the beginning of the light period of the fourth day. During the initial three days spontaneous activities remained constant, following the normal circadian distribution of rodents. Cycloheximide and tetrodotoxin administrations were followed by transient site-specific and activity-specific changes, which occurred only during the fourth and fifth day. The results show that protein synthesis inhibitors can be locally administered into the CNS at doses affecting only limited subcortical structures. The observed modifications of the three spontaneous activities were all transient and were always followed by complete recovery within 48 hours, thus confirming previous biochemical data. Therefore, the local injection of protein synthesis inhibitors, like tetrodotoxin, lidocaine or other compounds, can be employed to induce transient functional effects on well delimited brain structures in order to study the time-course of the mechanism of mnemonic trace formation.

Amygdala↗

PubMed1994

Post-training nucleus basalis magnocellularis functional tetrodotoxin blockade effects on passive avoidance consolidation in the rat.

The tetrodotoxin (TTX) functional ablation technique was employed in order to evaluate the temporal coordinates of the rat's nucleus basalis magnocellularis (NBM) involvement in memory trace processing. Under ketamine general anesthesia, TTX (10 ng in 1 microliter saline) was stereotaxically administered to rats, either in one or both NBMs. TTX was injected to different groups of rats, respectively 15 min, 6, 24, 48, 96 h after passive avoidance acquisition testing. The rats underwent retrieval testing 48 h later, i.e. after full recovery from TTX effects. Results show that: (1) monolateral TTX blockade significantly impairs PAR conditioned responding if induced up to 6 h but not 24 h after acquisition testing; (2) bilateral TTX blockade dramatically impairs passive avoidance responding up to a 48-h delay but not 96 h after acquisition testing. The results indicate a very profound involvement of NBM in passive avoidance response consolidation. The experimental evidence is discussed together with previous functional ablation findings concerning amygdala, parabrachial nuclei and neocortex.

Amygdala↗

PubMed1994

Passive avoidance response distribution by post-training substantia nigra functional tetrodotoxin inactivation in the rat.

The tetrodotoxin (TTX) functional ablation technique was employed to assess the temporal coordinates of rat's substantia nigra (SN) in memory processing. TTX (10 ng in 1 microliter saline) was stereotaxically administered to rats under general ketamine anesthesia, either bilaterally or unilaterally. TTX was injected in different groups of rats respectively 0.25, 6, 24, and 48 hours after passive avoidance acquisition testing. Rats always underwent retrieval testing 48 hours later, after full recovery from TTX effects. The results show that: i) unilateral TTX blockade significantly impairs PAR only up to 0.25 h and not 6 h after acquisition testing, and ii) bilateral TTX blockade dramatically disrupts passive avoidance responding up to 24 but not 48 hours after acquisition testing. The results indicate a much more important SN role in memory processing than was previously assessed. The experimental evidence is discussed both in relation to previous TTX functional ablation findings (amygdala, parabrachial nuclei, nucleus basalis magnocellularis) and in relation to SN anatomical and functional connections with other subcortical structures.

Animals↗

PubMed1993

Forced extinction as a means to evaluate consolidation gradient of a passive avoidance response in the rat.

Passive avoidance response (PAR) consolidation gradient, and US (footshock) intensity/engram strength relationship were investigated by means of specific forced extinction procedure (30 min detention in the shock box without receiving punishment) in Wistar rats trained in the light-dark box apparatus. Different groups of rats (punished either with 0.8 or 1.2 mA footshock intensity) underwent detention at different postacquisition time delays: immediately or 1, 2, 4 days after acquisition training. By means of this purely behavioral paradigm, designed to investigate a specific PAR memory trace, previous results obtained by using diverse and sometimes unspecific memory-disrupting agents were fully confirmed: PAR strength and consolidation gradient are positively related to US intensity. The influence of differential generalization effects on extinction is discussed. An unexpected finding was that from engrams that are experimentally shown to be of unequal resistance to disruption, equal conditioned responses are obtained.

Animals↗

PubMed1993

Minaprine facilitates acquisition and retrieval of an active avoidance response in the rat.

The nootropic activity of 3-(2-morpholino-ethylamino)-4-methyl-6-phenyl-pyridazine dihydrochloride (minaprine) has been investigated in intact male, adult Long Evans rats by means of an active avoidance paradigm. In the light-dark box apparatus, the rat had to learn the active avoidance response of going out of the normally preferred dark chamber to avoid electric foot-shocks. These were administered during one trial per day for 3 consecutive days (acquisition period). After a 72-h interval, rats underwent, for 3 consecutive days, one trial per day in which punishments were omitted (retrieval period). In the first experiment, rats were injected IP with minaprine (5, 10, and 25 mg/kg b.w.) 30 min before each trial of both periods. Rats injected with the two lower dosages showed better responding during the retrieval period than controls (saline). On the contrary, the highest dosage impaired active avoidance during both periods. In Experiment 2, minaprine (10 mg/kg b.w.) was administered either only during the acquisition or only during the retrieval period. In both instances, active avoidance was equally enhanced, if compared to controls (saline), only during the retrieval period. The results are discussed on the basis of the known facilitating activity on cholinergic systems of this compound. It is concluded that minaprine acts positively both on acquisition and retrieval of mnemonic traces.

Animals↗

PubMed1993

Differential effect of functional ablation of thalamic reticular nucleus on the acquisition of passive and active avoidance.

The possible contribution of inadvertent damage of the thalamic reticular nucleus to memory impairment caused by lesion of nucleus basalis magnocellularis (NBM) was examined. Rats carrying chronically implanted cannulae received unilateral injection of 3 ng tetrodotoxin (TTX) into the reticular nucleus either 60 min before (PRE) or 2 min after (POST) acquisition of a combined passive avoidance (PAR)--active avoidance (AAR) task. Three days later retrieval was tested during unilateral TTX blockade of the reticular nucleus in the same (IPSI) or in the opposite (CONTRA) hemisphere. Unilateral inactivation of the reticular nucleus affected neither acquisition nor retrieval of PAR, but interfered with AAR acquisition under the PRE conditions. AAR reacquisition was impaired in the PRE-CONTRA but not in the other groups. The effects of reticular nucleus blockade (AAR disruption without PAR impairment) contrast with AAR facilitation and PAR disruption after NBM lesions. It is concluded that the consequences of NBM damage are not enhanced by unintentional thalamic encroachment.

Animals↗

PubMed1993

Physical and optical shelter characteristics influence rat's preferences in a multiple Y-maze.

Rat's preference for covered or uncovered sections of a multiple Y-maze, measured as time spent under cover, was investigated. Surface area of covered and uncovered sections was the same. There were no light-intensity differences between uncovered and covered sections. Coverings were of two types: transparent or sanded plexiglas, affording respectively only physical or physical and optical protection. Both types of covering were placed either over discontinuous sections of the maze or continuously over one entire half of it. Male adult Wistar rats were employed. Rats exhibited maximal preference for the continuous sanded covering. They also exhibited a very similar significant preference for the continuous transparent covering and the discontinuous sanded one. Equal permanence time was measured in uncovered sections and under discontinuous transparent coverings. The results show that rats can recognize and choose shelter even when there is no light diminution under it. In fact they can very well discriminate between the several types of shelter, as shown by their significant longer permanence under the most protective and most continuous one. Finally, results are taken as basis for discussing whether the accepted "dark preference" of rats may be due solely to photophobia or also to the fact that normally darkness indicates a shelter.

Animals↗

PubMed1992

Engram activation reinstates the susceptibility of consolidated memory traces to retrograde amnesia by functional blockade of parabrachial nuclei.

Previous studies have shown that in rats the acquisition of a step-through passive avoidance reaction (PAR) in the light-dark box apparatus is disrupted by tetrodotoxin (TTX) inactivation of the parabrachial nuclei (PBN) 24 but not 48 h after the acquisition trial. The present experiment shows that TTX induces retrograde amnesia even when applied to the PBN 48 h after PAR acquisition only if it is preceded by a 30-min confinement (extinction) or by a footshock (retraining) in the dark compartment. These stimuli, independently of their sign, induce quantitatively comparable TTX disrupting effects. This happens notwithstanding the fact that these stimuli are too weak to modify PAR under control conditions. This paradoxical finding suggests that engram vulnerability may not be a simple inverse function of its recency but that it may reflect a reactivation of the neural circuits involved in memory trace formation. Consolidated engrams become again vulnerable only when contextual cue stimuli are presented shortly before the application of the disrupting procedure.

Amnesia, Retrograde↗

PubMed1992

Duration of retrograde amnesia induced by tetrodotoxin inactivation of the parabrachial nuclei is inversely related to the intensity of footshock in rat's passive avoidance response.

Previous work has demonstrated that in rats post-trial bilateral functional blockade of the parabrachial nuclei by local injection of tetrodotoxin (10 ng in 1 microliter) partially disrupts retention of an overtrained passive avoidance response. The time-course of functional blockade disrupting effects on passive avoidance response has been studied by altering both the acquisition-tetrodotoxin injection interval and footshock intensity as independent variables. When week footshocks (0.8 mA) were delivered, functional ablation of the parabrachial nuclei was still effective when induced up to 8 days after acquisition training. On the other hand, when rats were shocked with the stronger stimuli (1.2 mA), 2 days after acquisition functional ablation was no longer effective. The results are discussed in terms of unconditioned stimulus (US) intensity and engram consolidation.

Amnesia, Retrograde↗

PubMed1992

Time-dependent disruption of passive avoidance acquisition by post-training intra-amygdala injection of tetrodotoxin in rats.

The role of the amygdala (AM) in the consolidation of the passive avoidance reaction (PAR) has been examined with the tetrodotoxin (TTX)-induced functional block of this structure. Rats were trained in the step-through PAR and anesthetized with ketamine. TTX injected immediately after acquisition into both AM (2 x 10 ng) significantly reduced avoidance of the dark compartment in the retrieval test performed two days later. The amnesic effect was significant when the acquisition--TTX delay was prolonged to 90 min but not to 6 h or 24 h. Earlier research indicated that TTX blockade of the parabrachial nuclei caused similar PAR disruption when elicited 24 h but not 48 h after acquisition. Comparison of the TTX-induced retrograde amnesias indicates that the two structures play different roles in the formation of the PAR engram.

Amnesia, Retrograde↗

PubMed1992

Minaprine cancels scopolamine effects on the rat's acquisition of passive avoidance responses in two multitrial paradigms.

The antiamnesic activity of minaprine has been studied in male Wistar rats. Two multitrial paradigms were employed: the light-dark box test (aversive stimulus: 0.6-mA foot-shocks) and the tail-handling test (aversive stimulus: manual tail-handling). In both paradigms, intraperitoneal scopolamine administration 30 min before testing significantly impaired the acquisition of the passive avoidance conditioned response. There were no significant differences in either paradigm between control rats and those to whom scopolamine and minaprine were simultaneously administered. These results show that minaprine fully protects the acquisition process of conditioned responses against scopolamine impairment not only in one-trial tests but also in multitrial paradigms. The effects of minaprine in reversing memory deficits are discussed in relation to its stimulating activity on central cholinergic systems.

Amnesia↗

PubMed1992

Postacquisition injection of tetrodotoxin into the parabrachial nuclei elicits partial disruption of passive avoidance reaction in rats.

The recent discovery that post-trial functional blockade of the parabrachial nuclei by intracerebral injection of 10 ng tetrodotoxin (TTX) disrupts acquisition of conditioned taste aversion (CTA) (Ivanova & Bures, 1990a,b) has prompted attempts to ascertain the role of this structure in other types of inhibitory learning. In Experiment 1, rats with implanted parabrachial cannulae were trained in a step-through avoidance task and received bilateral TTX (2 x 10 ng) immediately after the acquisition trial; they displayed significantly weakened avoidance of the shock compartment 2 days later. In Experiment 2, rats were anesthetized with pentobarbital (50 mg/kg) immediately after passive avoidance acquisition and received parabrachial TTX 15 min later; whereas anesthesia alone left the passive avoidance reaction (PAR) unaffected, TTX elicited similar disruption as in unanesthetized animals. In Experiment 3, TTX was injected in anesthetized animals 0, 1, 2, or 4 days after PAR acquisition. The amnesic effect was significant when the acquisition-TTX delay had been prolonged to 24 but not to 48 or 96 h. Since CTA is disrupted by reversible blockade of parabrachial nuclei and of the adjacent reticular formation elicited up to 4 days after acquisition (Ivanova & Bures, 1990b), PAR seems to be impaired to a lesser degree and for a shorter time than CTA by similar TTX treatment.

Amygdala↗

PubMed1992

Lateralized contributions of the cerebral cortex, parabrachial nucleus, and amygdala to acquisition and retrieval of passive avoidance reaction in rats: a functional ablation study.

Reversible blockade of the neocortex by spreading depression and of the parabrachial nucleus (PBN) and amygdala (AMG) by tetrodotoxin (TTX) injection was used to study lateralization of passive avoidance reaction (PAR) engrams in rats. In Experiment 1, PAR acquisition was not disrupted by posttrial TTX applied into the PBN or AMG or into both of these structures in the same hemisphere but was impaired when the AMG and PBN were blocked in opposite hemispheres. In Experiment 2, retrieval of PAR acquired with intact brain was not impaired by unilateral TTX blockade of the AMG. In Experiment 3, PAR was acquired with posttrial TTX blockade of the AMG and PBN in one hemisphere. Full or partial block of PAR retrieval was induced by functional decortication of the contra- or ipsilateral hemisphere, respectively, whereas blockade of either AMG was ineffective. It is concluded that PAR acquisition requires ipsilateral interaction of the AMG and PBN and that the two hemicortices contribute differentially to the retrieval of engrams formed under such conditions.

Amygdala↗

PubMed1991

The behavior of the homozygous and heterozygous sub-types of rats which are genetically-selected for diabetes insipidus: a comparison with Long Evans and Wistar stocks.

Several aspects of spontaneous and conditioned behavior (food and water intake, locomotion and emotionality, passive and active avoidance acquisition and retention) of standard (albino and pigmented) rats, and rats heterozygous (HEDI) and homozygous (HODI) for diabetes insipidus, are reviewed. As would be expected, HODI rats have been repeatedly found to consume far more fluid than either HEDI or control rats. Pigmented rats appear to be more active than albinos. HODI rats exhibit less marked emotional responses than do control rats, among which the pigmented ones exhibit the highest emotionality. Light aversion is more evident in albino than in pigmented rats. No differences are found among HEDI, HODI and normal Long Evans rats. It is quite difficult to provide a clear-cut statement concerning inter-strain differences in passive avoidance behavior, possibly because of the variety of techniques employed. In any case, HODI rats do not perform worse than normal controls do. In one-way active avoidance paradigms, pigmented rats perform better than albinos, and the performance of HODI rats does not differ from that of controls. In two-way avoidance paradigms, albinos appear to outperform pigmented rats. Once again, there are no obvious differences between HODI and control animals. In addition to indicating that HODI rats may actually be less emotional than the other groups of rats reviewed here, the studies described once again fail to confirm the previously alleged functions of vasopressin in memory consolidation.

Animals↗

PubMed1991

Effects of nucleus basolateralis amygdalae neurotoxic lesions on aversive conditioning in the rat.

After bilateral stereotaxic administration of ibotenic acid on the n. basolateralis amygdalae, male adult rats were tested in the light-dark box apparatus to measure the time-course of the acquisition and retention of passive and active avoidance responses. The results show that after the lesions both passive avoidance and active avoidance acquisition were impaired. Passive avoidance responses were retained quite well, while active avoidance responses disappeared quickly. Conditioned freezing was almost completely absent. Thus it appears that the n. basolateralis plays a facilitatory role in all the conditioned responses which were investigated.

Amygdala↗

PubMed1991

Effects of nucleus basolateralis amygdalae neurotoxic lesions on some spontaneous activities in the rat.

Drinking, feeding, locomotion and exploratory activity of male Wistar rats were assessed after bilateral stereotaxic administration of ibotenic acid in the nucleus basolateralis amygdalae. Feeding, drinking and locomotion were measured in an activity cage, while exploratory activity was determined in a multiple Y-maze. In the 24-hour cycle, lesioned animals exhibited unvaried feeding, decreased drinking and increased locomotion. Exploration was also increased. The results show that this nucleus is not involved in quantitative feeding control, while it does exert a significant facilitatory influence on drinking. It also exerts an inhibitory influence on exploration and on locomotion.

Amygdala↗