The irrelevancy of the inter-trial interval in delay-discounting experiments on an animal model of ADHD.

Delay discounting involves choosing between a small, immediate reward, and a larger but delayed one. As the delay between choice and large reward gets longer, people with ADHD tend to become impulsive faster than controls, indicated by a switch in preference from the large to the smaller reward. Choosing the smaller reward when the larger is considered reward maximizing is labeled impulsive behaviour.

Female rats release a trapped cagemate following shaping of the door opening response: Opening latency when the restrainer was baited with food, was empty, or contained a cagemate.

Research on pro-social rat behaviour is growing within the fields of comparative psychology and social neuroscience. However, much work remains on mapping important variables influencing this behaviour, and there is even disagreement on whether this behaviour is empathetically motivated and correctly labelled pro-social, or whether the behaviour is motivated by social contact. The present study used the helping behaviour paradigm where a rat can release a familiar cagemate from a restrainer.

Patterns of motor activity in spontaneously hypertensive rats compared to Wistar Kyoto rats.

Background: Increased motor activity is a defining characteristic of patients with ADHD, and spontaneously hypertensive rats have been suggested to be an animal model of this disorder. In the present study, we wanted to use linear and non-linear methods to explore differences in motor activity patterns in SHR/NCrl rats compared to Wistar Kyoto (WKY/NHsd) rats.

Methods: A total number of 42 rats (23 SHR/NCrl and 19 WKY/NHsd, male and female) were tested.

Gender-dependent and genotype-sensitive monoaminergic changes induced by polychlorinated biphenyl 153 in the rat brain.

Polychlorinated biphenyls (PCBs) are present as ortho- and non-ortho-substituted PCBs, with most of the ortho-substituted congeners being neurotoxic. The present study examined effects of the ortho-substituted PCB 153 on dopamine, serotonin and amino acid neurotransmitters in the neostriatum of both male and female Wistar Kyoto (WKY) and spontaneously hypertensive rat (SHR) genotypes. PCB 153 exposure at p8, p14 and p20 had no effects on levels of these transmitters when examined at p55, but led to increased levels of both homovanillic acid and 5-hydroxyindoleacetic acid, the degradation products of dopamine and serotonin, respectively, in all groups except the female SHR.

Behavioral changes following PCB 153 exposure in the spontaneously hypertensive rat - an animal model of Attention-Deficit/Hyperactivity Disorder.

Background: Attention-Deficit/Hyperactivity Disorder (ADHD) is a behavioral disorder affecting 3-5% of children. Although ADHD is highly heritable, environmental factors like exposure during early development to various toxic substances like polychlorinated biphenyls (PCBs) may contribute to the prevalence. PCBs are a group of chemical industrial compounds with adverse effects on neurobiological and cognitive functioning, and may produce behavioral impairments that share significant similarities with ADHD.

Marine Ο-3 polyunsaturated fatty acids induce sex-specific changes in reinforcer-controlled behaviour and neurotransmitter metabolism in a spontaneously hypertensive rat model of ADHD.

Background: Previous reports suggest that omega-3 (n-3) polyunsaturated fatty acids (PUFA) supplements may reduce ADHD-like behaviour. Our aim was to investigate potential effects of n-3 PUFA supplementation in an animal model of ADHD.

Methods: We used spontaneously hypertensive rats (SHR).

Postnatal exposure to PCB 153 and PCB 180, but not to PCB 52, produces changes in activity level and stimulus control in outbred male Wistar Kyoto rats.

Background: Polychlorinated biphenyls (PCBs) are a class of organic compounds that bioaccumulate due to their chemical stability and lipophilic properties. Humans are prenatally exposed via trans-placental transfer, through breast milk as infants, and through fish, seafood and fatty foods as adolescents and adults. Exposure has several reported effects ranging from developmental abnormalities to cognitive and motor deficiencies.

Rat models of ADHD.

Showing that an animal is hyperactive is not sufficient for it to be accepted as a model of ADHD. Based on behavioral, genetic, and neurobiological data, the spontaneously hypertensive rat (SHR) obtained from Charles River, Germany, (SHR/NCrl) is at present the best-validated animal model of ADHD. One Wistar Kyoto substrain (WKY/NHsd), obtained from Harlan, UK, is its most appropriate control.

The spontaneously hypertensive rat model of ADHD--the importance of selecting the appropriate reference strain.

Although several molecular and genetic manipulations may produce hyperactive animals, hyperactivity alone is insufficient for the animal to qualify as a model of ADHD. Based on a wider range of criteria - behavioral, genetic and neurobiological - the spontaneously hypertensive rat (SHR) obtained from Charles River, Germany (SHR/NCrl) at present constitutes the best validated animal model of ADHD combined subtype (ADHD-C), and the Wistar Kyoto substrain obtained from Harlan, UK (WKY/NHsd) is its most appropriate control. Although other rat strains may behave like WKY/NHsd rats, genetic results indicate significant differences when compared to the WKY/NHsd substrain, making them less suitable controls for the SHR/NCrl.

Origins of altered reinforcement effects in ADHD.

Attention-deficit/hyperactivity disorder (ADHD), characterized by hyperactivity, impulsiveness and deficient sustained attention, is one of the most common and persistent behavioral disorders of childhood. ADHD is associated with catecholamine dysfunction. The catecholamines are important for response selection and memory formation, and dopamine in particular is important for reinforcement of successful behavior.

Progressive ratio schedules of reinforcement.

Pigeons' pecks produced grain under progressive ratio (PR) schedules, whose response requirements increased systematically within sessions. Experiment 1 compared arithmetic (AP) and geometric (GP) progressions. Response rates increased as a function of the component ratio requirement, then decreased linearly (AP) or asymptotically (GP).

Behavioral variability, elimination of responses, and delay-of-reinforcement gradients in SHR and WKY rats.

Background: Attention-deficit/hyperactivity disorder (ADHD) is characterized by a pattern of inattention, hyperactivity, and impulsivity that is cross-situational, persistent, and produces social and academic impairment. Research has shown that reinforcement processes are altered in ADHD. The dynamic developmental theory has suggested that a steepened delay-of-reinforcement gradient and deficient extinction of behavior produce behavioral symptoms of ADHD and increased behavioral variability.

Response variability in Attention-Deficit/Hyperactivity Disorder: a neuronal and glial energetics hypothesis.

Background: Current concepts of Attention-Deficit/Hyperactivity Disorder (ADHD) emphasize the role of higher-order cognitive functions and reinforcement processes attributed to structural and biochemical anomalies in cortical and limbic neural networks innervated by the monoamines, dopamine, noradrenaline and serotonin. However, these explanations do not account for the ubiquitous findings in ADHD of intra-individual performance variability, particularly on tasks that require continual responses to rapid, externally-paced stimuli. Nor do they consider attention as a temporal process dependent upon a continuous energy supply for efficient and consistent function.

A dynamic developmental theory of attention-deficit/hyperactivity disorder (ADHD) predominantly hyperactive/impulsive and combined subtypes.

Attention-deficit/hyperactivity disorder (ADHD) is currently defined as a cognitive/behavioral developmental disorder where all clinical criteria are behavioral. Inattentiveness, overactivity, and impulsiveness are presently regarded as the main clinical symptoms. The dynamic developmental behavioral theory is based on the hypothesis that altered dopaminergic function plays a pivotal role by failing to modulate nondopaminergic (primarily glutamate and GABA) signal transmission appropriately.

Animal models of attention-deficit hyperactivity disorder.

Although animals cannot be used to study complex human behaviour such as language, they do have similar basic functions. In fact, human disorders that have animal models are better understood than disorders that do not. ADHD is a heterogeneous disorder.

Rodent models of attention-deficit/hyperactivity disorder.

An ideal animal model should be similar to the disorder it models in terms of etiology, biochemistry, symptomatology, and treatment. Animal models provide several advantages over clinical research: simpler nervous systems, easily interpreted behaviors, genetic homogeneity, easily controlled environment, and a greater variety of interventions. Attention-deficit/hyperactivity disorder (ADHD) is a neurobehavioral disorder of childhood onset that is characterized by inattentiveness, hyperactivity, and impulsiveness.

Effects of delayed reinforcers on the behavior of an animal model of attention-deficit/hyperactivity disorder (ADHD).

Attention-deficit/hyperactivity disorder (ADHD), affecting 3-5% of grade-school children, is a behavioral disorder characterized by developmentally inappropriate levels of inattention, hyperactivity, and impulsivity. It has been suggested that the symptoms are caused by altered reinforcement and extinction processes, behaviorally described as an abnormally short and steep delay-of-reinforcement gradient in ADHD. The present study tested predictions from the suggested shortened and steepened delay gradient in ADHD in an animal model, the spontaneously hypertensive rats (SHRs).

Behavioral effects of intra-cranial self-stimulation in an animal model of attention-deficit/hyperactivity disorder (ADHD).

Attention deficit/hyperactivity disorder (ADHD), characterized by inappropriate levels of activity, attention, and impulsivity, has been suggested to be caused by changes in reinforcement and extinction processes possibly linked to dysfunctioning dopamine systems. The present study investigated reinforcement processes in spontaneously hypertensive rats (SHR), an animal model of ADHD. Using intra-cranial self-stimulation (ICSS), behavioral effects of varying current intensity, reinforcer density, and reinforcer delay were tested.

Slower extinction of responses maintained by intra-cranial self-stimulation (ICSS) in an animal model of attention-deficit/hyperactivity disorder (ADHD).

Children with attention-deficit/hyperactivity disorder (ADHD) show performance deficits and excessive motor activity during extinction and in situations where no reinforcer can be identified, suggesting an extinction deficit in ADHD possibly linked to dopamine dysfunction. The present study examined extinction of responding previously maintained by intra-cranial self-stimulation (ICSS) in spontaneously hypertensive rats (SHR), an animal model of ADHD using three different extinction procedures. Delivery of electrical pulses were terminated altogether or presented independently of responding using two different current intensities.

The control of responsiveness in ADHD by catecholamines: evidence for dopaminergic, noradrenergic and interactive roles.

We explore the neurobiological bases of attention deficit hyperactivity disorder (ADHD) from the viewpoint of the neurochemistry and psychopharmacology of the catecholamine-based behavioural systems. The contributions of dopamine (DA) and noradrenaline (NA) neurotransmission to the motor and cognitive symptoms of ADHD (e.g.

Response disinhibition may be explained as an extinction deficit in an animal model of attention-deficit/hyperactivity disorder (ADHD).

Attention-deficit/hyperactivity disorder (ADHD) is a disorder affecting between 2 and 12% of grade-school children disturbing social, academic, and occupational functioning. Problems related to social adjustment and functioning and/or psychiatric problems will exist in 50-70% of adolescents and young adults diagnosed with ADHD as children. It has been suggested that altered reinforcement and extinction processes may cause the symptoms of ADHD.

Attention-deficit/hyperactivity disorder (ADHD) behaviour explained by dysfunctioning reinforcement and extinction processes.

Inattentiveness, overactivity and impulsiveness are presently regarded as the main clinical symptoms of attention-deficit/hyperactivity disorder (ADHD). Inattention is, however, a characteristic of most psychiatric disorders. It is argued that the ADHD Inattentive subtype may have heterogeneous origins and be qualitatively different from the ADHD Hyperactive/Impulsive subtype.