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PubMed1979

Possible involvement of serotonin in extinction.

In Experiment 1, rats were trained to leverpress for continuous reinforcement with food; half were then intubated with the serotonin synthesis inhibitor parachlorophenylalanine (PCPA: 400 mg/kg) and half with water. In extinction the PCPA-treated rats responded at a higher rate. In Experiment 2, rats were trained on a random interval schedule and then assigned to two groups, treated as in Experiment 1, and tested in extinction. There was no significant difference in the resistance to extinction of the two groups. In Experiment 3, the responding of rats trained in a punished stepdown response paradigm and then given an intragastric injection of PCPA took longer to recover than the responding of water-injected controls. These observations suggest that serotonergic neurons might play a role in extinction processes.

Animals↗
PubMed1979

Neurochemical basis of the dorsal bundle extinction effect.

Injection of 6-hydroxydopamine into the mesencephalon of the rat has been found to cause resistance to extinction on continuously reinforced schedules. The neurochemical basis of this effect was investigated by using another concentration of 6-hydroxydopamine and by another position of injection. Severe depletion of forebrain noradrenaline was found after these injections with no change in dopamine, serotonin, cholinergic or GABAergic parameters in any brain area measured. The noradrenergic nature of the effect was further shown by the reversal fo the usual behavioural effect following pretreatment with a noradrenaline uptake inhibitor (desimipramine, 25 mg/kg 30 min prior to intracerebral injection of 6-hydroxydopamine). This rules out non-specific damage caused by the 6-hydroxydopamine as the neurochemical basis of the dorsal bundle extinction effect. Failure to find resistance to extinction after either kainic acid or 5-7 dihydroxytryptamine injection seems also to exclude respectively cell body loss at the injection site or damage to serotonergic systems. It is concluded that the dorsal bundle extinction effect is noradrenergic in nature.

5,7-Dihydroxytryptamine↗
PubMed1976

Migration, extinction, and alary morphism in water-striders (Gerris Fabr.)

A migration-extinction model has been developed for the analysis of alary polymorphism and its adaptive significance in univoltine populations of water-striders (Gerris). It is assumed that all actual and potential population sites are identical with respect to all relevant variables, i.e. that populations do not live in a 'harlequin' environment. The model can be applied to other groups with alary polymorphism. The effects of isolation, environmental stability, and environmental productivity are discussed, with numerical examples. Isolation and stability enhance the optimality of short-wingedness, while temporariness of population sites selects for long-wingedness. Optima cannot always be realized. The models reveal several critical variables which are of interest in the ecological genetics of Gerris and which should be measured in natural populations: (a) extinction probabilities (a distinction being drawn between extinction due to drying up of the population site and extinction due to other causes), (b) extent of passive dispersal, and (c) the proportion of colonized population sites in a large geographical region.

Adaptation, Biological↗
PubMed1976

Effects of intraventricular glutamic acid on the acquisition, performance, and extinction of an operant response, and on general activity.

This study was designed to investigate the effects of intracerebral injections of glutamic acid on acquisition and extinction of a bar-press response, performance of that response, and behavior activity. Nineteen food-deprived rats bearing chronic ventricular cannulae were tested in operant conditioning chambers or in an open field. Just prior to each testing session each animal was injected intraventricularly with 10 mul of either normal or acidified saline solution (control groups), or 10 mul of 100 mMol glutamic acid solution. Acquisition of the bar-pressing response by the glutamic acid group was significantly retarded as compared to the control groups, and the responding of the glutamic acid group was suppressed during the beginning of the first few sessions of testing on a fixed-interval schedule and during extinction. Other behavioral measures, such as operant level, performance of the response on a continuous schedule, performance on fixed-interval and extinction schedules except during the start of the first few sessions, and behavioral activity, were either unaffected or only slightly affected. It is concluded that interference with the normal neurophysiological activity of glutamic acid in the central nervous system interferes with learning and suppresses behavioral output in certain situations.

Animals↗
PubMedDate not supplied

Personality and conditioning: factors of classical CR acquisition and extinction and their relationship to personality types.

A number of psychophysiological, cognitive and personality measures, and classical appetitive and aversive SR acquisition and extinction rates were taken from a sample of 25 male undergraduate volunteers. Principal Components Analysis of the data revealed general acquisition and extinction factors which were indexed by the psychophysiological variables. Regression analyses showed additionally that Eysenck's E-I dimension predicts both acquisition and extinction rates, and that imagery may be an important mediational variable in CR acquisition.

Adolescent↗
PubMed1976

Extinction-induced mirror responding as a baseline for studying drug effects on aggression.

Pigeons worked individually in a chamber containing a response key and a mirror. Responding on the key was controlled by a multiple schedule in which a brief period of continuous food reinforcement alternated with a 5 min period of extinction. Under baseline conditions, aggressive behavior (responding on the mirror) occurred at the onset of each extinction period. After 10 saline control sessions, 5 mg/kg of chlordiazepoxide was injected IM 30 min presession for 60 daily sessions. The drug initially produced a marked decrease in aggressive behavior but had little or no effect on key pecking. The aggressive behavior generally remained suppressed during the chronic drug regimen and returned to control levels when the drug was withdrawn. It was concluded that the technique of extinction-induced mirror responding in pigeons provides a stable, sensitive and recoverable baseline for objectively assessing selective drug effects on aggression.

Aggression↗
PubMed1977

Protein synthesis inhibition and memory for pole jump active avoidance and extinction.

This study utilizes a pole jump active avoidance task to investigate the effects of protein synthesis on memory formation. An extinction training procedure for this task is also described. Amnesia for extinction is produced by inhibition of protein synthesis and is also demonstrated by active responding, so it is clear that there is no general impairment sufficient to disrupt motor skill, motivation, or retrieval of stored memories. It was found that while inhibition of protein synthesis in brain for 2 hr did not produce amnesia, inhibition for 6 to 8 hr did. These results demonstrate that for both shock-motivated learning and non-shock motivated extinction learning, the duration of inhibition of protein synthesis is important in determining whether amnesia occurs. We conclude that inhibition of cerebral protein synthesis can best account for amnesia induced by anisomycin, cycloheximide, and acetoxycycloheximide.

Animals↗
PubMed1979

Forebrain noradrenaline depletion blocks the release by chlordiazepoxide of behavioral extinction in the rat.

The interaction between chlordiazepoxide (CDP) and forebrain noradrenaline (NA) was investigated in rats with bilateral radiofrequency lesions of the noradrenergic dorsal tegmental bundle (DTB). Forebrain NA was reduced to 35% of control by the DTB lesions; hypothalamic NA and dopamine were unchanged. Rats were trained on a straight alley runway task for food reward. During extinction of the runway task, CDP significantly increased extinction responding in sham lesion animals but not in DTB lesion animals. Thus, CDP was ineffective in increasing resistance to extinction responding in the runway task in animals with significant depletion of forebrain NA.

Animals↗
PubMed2026

The paradoxical extinction: Exploring signatures of assortative mating as a possible mechanism that maintains canonical Red Wolf genetic ancestry in the American Gulf Coast canids.

Admixed genomes, particularly those with an evolutionary history of genetic exchange with an endangered or extinct species, are valued for innovative and unconventional conservation actions. Here, we show the substantial conservation value that the admixed canids of the Gulf Coast have as they retain high amounts of contemporary Red Wolf ancestry and unique genetic variation of past Red Wolf lineages (e.g. ghost ancestry). We analyzed 54,439 loci genotyped across the genome of 413 North American canids and investigated the role that assortative mating with respect to ancestry proportions played in the retention of endangered genetic variation. We report high correlations of inter-chromosomal ancestry proportions that varied with geographic location along Texas and Louisiana Gulf Coast populations, with the stronger signatures reported in the latter. We found that models of assortative mating promoted greater ancestry variance compared with random mating leading to increased efficiency of selection for Red Wolf and ghost alleles. Despite the Red Wolf being extinct in the wild, original, and ghost genomic variation persists in Gulf Coast admixed canids. We suggest two conservation strategies that value and preserve this unique and endangered genomic variation through designed breeding programs. Ultimately the incorporation of this ghost genetic variation would be valuable to boost the genetic viability of the ex situ Red Wolf breeding program, create in situ redundancy, and avoid extinction for this endemic American wolf species.

Animals↗
PubMed1979

Personality and extinction of a conditioned electrodermal response.

This study investigated personality differences in extinction of a conditioned EDR. The subjects were selected on the basis of EPI neuroticism and impulsivity scores. Subjects with scores on, or near, the sample means were excluded. Fifty-one subjects underwent an aversive discrimination conditioning procedure. The reinforcement was 75 per cent, the UCS was 100 dB white noise for 1 sec, while the CS was one of five different coloured lights of 2 sec duration. The UCS was presented at CS termination. Subjects were informed of the CS--UCS contingency before the acquisition phase and informed of the onset of the extinction phase. Subjects high on impulsivity showed significantly (P less than 0.01) greater extinction of the discrimination than subjects low on impulsivity.

Conditioning, Classical↗
PubMed1979

Neonatal androgen effects on conditioned emotional response extinction of adult rats under various hormonal regimens.

Intact male rats and spayed female rats received 0.5 mg testosterone propionate in the first 24 hours after birth. They were divided into different groups, administered peanut oil, progesterone, oestradiol benzoate and testosterone propionate in adulthood. The animals were conditioned to fear with a shock paired sound. The experimental test consisted of investigating the conditioned emotional response (CER) extinction. It was verified that as to conditioned emotional response extinction, neonatally androgenized males were different from control males; neonatally androgenized females, testosterone propionate treated in adulthood were also different from control females. There was no significant difference between neonatally androgenized females oestradiol benzoate treated in adulthood and their control group. In comparing neonatally androgenized females having different hormonal treatment in adulthood, we verified that testosterone propionate treated females were significantly different from those treated with progesterone. On the other hand, neonatally androgenized females treated with oestradiol benzoate in adulthood were different from those that have had the same hormonal manipulation in neonatal period, but that were injected with progesterone in adulthood. It was concluded that conditioned emotional response extinction is facilitated by neonatal androgenization in non-oestrogenized male and female rats.

Age Factors↗
PubMedDate not supplied

[Effect of electric stimulation of the somatosensory cortex and caudate nucleus on extinctive inhibition of a conditioned alimentary reflex to sound].

In experiments performed on 9 dogs with alimentary method, extinctive inhibition was deepened and its elaboration was aceelerated by electrical stimulation of somatosensory and motor cortical areas and ventral segment of the caudate nucleus head. The extinction of the conditioned reflex was slowed down by stimulation of the anterolateral gyrus and the central segment of the caudate nucleus head. General motor excitation of animals during stimulation of the dorsal zone of caudate nucleus head impaired the elaboration of extinctive inhibition.

Animals↗
PubMedDate not supplied

[Changes in the cholinosensitivity of sensomotor cortex neurons during conditioned reflex extinction].

Characteristics of neuronal responses of the sensorimotor cortex to ionophoretically administered neuromediators (acetylcholine, L-glutamate) were studied in rabbit in the course of extinction of conditioned defensive reflex. In the majority of neurones the extinction of the conditioned reflex is accompanied by a drop of cholinosensitivity. In a number of neurones the extinction of reflexes either does not change the reaction to acetylcholine, or enhances it. The analysis of these reactions permits to assume the existence of a group of neurones directly involved in the formation, fixation and storage of the temporary connection.

Acetylcholine↗
PubMed1977

[Avoidance learning in a social situation- extinction resistance and defense reaction under stress. A pilot study].

Two successive experiments were conducted resulting from observations of the stability (resistance to extinction) of avoidance reactions and the manifestation of such reactions beyond the specific avoidance conditions in which they were acquired: a) 15 subjects were set the task to avoid an aversive acoustic stimulus for a helpless experimental partner. They could achieve this by reacting with contraction of either the forearm or the calf muscles in a difficult discrimination task. The stability of these avoidance reactions was assessed on different levels of forced extinction. Measures taken were HR, GSR and EMG of the avoidance reactions. Specific courses of the two autonomous measures evolved (Fig. 1,2). 14 of the 15 experimental subjects showed the avoidance behaviour during all phases of forced extinction. b) Six weeks after the experimental subjects had acquired the motor avoidance reactions all subjects were exposed to a relatively unspecific stress situation. Comparisons between experimental and control group (which consisted of the experimental partners) showed a tendency but not a significant difference as far as the reaction of the calf muscles was concerned. Contraction of the forearm muscles, however, occurred significantly more often in the experimental group. The subjects executed these reactions without being aware of it.

Adult↗
PubMed1978

Stimulus intensity effects of acute extinction of the CER in rats.

Two groups of 9 rats were trained in the conditioned emotional response (CER) consisting of suppression of food-motivated behavior as a consequence of the pairing of white noise with unavoidable shock. One group was trained and then extinguished with an 80 dB white noise value and the other with the 50 dB white noise intensity as the conditioned stimulus (CS). The CER acquisition was faster with the more intense CS, however, on the last training day, conditioned suppression reached the same asymptotic level in both groups. Then an acute extinction procedure was introduced, wherein the CS was presented only once a day and lasted continuously until the end of the session with no US presentation during this period. This procedure was repeated over several consecutive days. During the first prolonged CS action, CER extinction was more rapid in the 50- than in 80-dB group. However, on the next extinction day the amount of suppression was less with the more intense CS. The results were discussed in terms of CS intensity effects on learning and performance of the conditioned response.

Acoustic Stimulation↗
PubMed1975

Extinction of liver-specific functions in hybrids between differentiated and dedifferentiated rat hepatoma cells.

A cross has been performed between dedifferentiated rat hepatoma cells and the differentiated cells from which they were derived. 10 hybrid clones, containing the complete chromosome sets of both parents, show extinction of 4 liver-specific enzymes: tyrosine aminotransferase (E.C. 2.6.1.5), alanine aminotransferase (E.C. 2.6.1.2), and the liver-specific isozymes of alcohol dehydrogenase (E.C. 1.1.1.1) and aldolase (E.C. 4.1.2.13). Moreover, the 4 hybrid clones examined do not produce albumin . The only function of the differentiated parent which is not extinguished in the hybrid cells is inducibility of the aminotransferases. For 3 of the hybrid clones, extinction of 3 of the 4 enzymes is incomplete, but these clones do not differ in modal chromosome number from those which show more complete extinction of the enzymes. Subcloning of several of the hybrids revealed that the phenotype of the hybrids is very stable; 4 subclones showing reexpression of intermediate levels of the enzymes are characterized. These results show that dedifferentiation of the parental cells is not due to the simple loss of some factor required for the maintenance of expression of differentiated functions, and suggest that dedifferentiation is due to the activation of some control mechanism, whose final effect is negative, and which may be a part of the epigenotype of the embryonic hepatocyte.

Alanine Transaminase↗
PubMed2025

Time-lagged genomic erosion and future environmental risks in a bird on the brink of extinction.

Global biodiversity is rapidly declining due to habitat degradation and genomic erosion, highlighting the urgent need to monitor endangered species and their genetic health. Temporal genomics and ecological modelling offer finer resolution than single-time-point measurements, providing a comprehensive view of species' recent and future trajectories. We investigated genomic erosion and environmental suitability in the critically endangered regent honeyeater (Anthochaera phrygia) by sequencing whole genomes of historical and modern specimens and building multi-temporal species distribution models (SDMs) across the last century. The species has declined from hundreds of thousands of individuals to fewer than 300 over the past 100 years. SDMs correctly predicted known patterns of local extinction in southeast Australia. Our demographic reconstructions revealed a gradual population decline from 2000 to 2500 years ago, sharply accelerating in the last 500 years due to climate variability and habitat loss. Despite this substantial demographic collapse, the regent honeyeater has lost only 9% of its genetic diversity, with no evidence of inbreeding or connectivity loss. Also, it exhibits higher diversity than many other threatened bird species. Forward-in-time genomic simulations indicate that this time lag between population decline and genetic diversity loss conceals the risk of ongoing genomic erosion into a future of rapidly degrading environmental suitability. Our work underscores the need for targeted conservation efforts and continuous genetic monitoring to prevent species extinction.

Animals↗