Hyperlocomotion, also known as locomotor hyperactivity, hyperactivity, or increased locomotor activity, is an effect of certain drugs in animals in which locomotor activity is increased. [1] More specifically, it is an effect induced by dopamine releasing agents and psychostimulants like amphetamine and methamphetamine and by NMDA receptor antagonists and dissociative hallucinogens like dizocilpine (MK-801) and phencyclidine (PCP). [1] [2] [3] [4] Stimulation of locomotor activity is thought to be mediated by increased signaling in the nucleus accumbens. [5] [6]
Drug-induced hyperlocomotion can be reversed by various drugs, such as antipsychotics acting as dopamine D2 receptor antagonists. [1] [3] Reversal of drug-induced hyperlocomotion has been used as an animal test of drug antipsychotic-like activity. [1] [3] Amphetamines and NMDA receptor antagonists likewise induce stereotypies, and reversal of these stereotypies is also employed as a test of drug antipsychotic-like activity. [1] [3]
Certain antidepressants, including the dopamine reuptake inhibitors amineptine, bupropion, and nomifensine, also increase spontaneous locomotor activity in animals. [7] [8] Conversely, most other antidepressants do not do so, and instead often actually show behavioral sedation in this test. [7] [5] [9] The dopamine reuptake inhibitor cocaine increases locomotor activity similarly to amphetamines. [4] Atypical dopamine reuptake inhibitors like modafinil do not produce hyperlocomotion in animals. [4] Direct dopamine receptor agonists like apomorphine show biphasic effects, decreasing locomotor activity at low doses and increasing locomotor activity at high doses. [5]
Other similar effects include stereotypy, exploratory behavior, climbing behavior, and jumping behavior. [10] [2] [3] Amphetamines induce stereotypies in addition to hyperlocomotion. [2] [3] Apomorphine induces stereotypy and climbing behavior. [2] The dopamine precursor levodopa (L-DOPA) induces jumping behavior. [2] These effects can all be reversed by antipsychotics. [2]
Psychopharmacology is the scientific study of the effects drugs have on mood, sensation, thinking, behavior, judgment and evaluation, and memory. It is distinguished from neuropsychopharmacology, which emphasizes the correlation between drug-induced changes in the functioning of cells in the nervous system and changes in consciousness and behavior.
Aripiprazole, sold under the brand names Abilify and Aristada, among others, is an atypical antipsychotic. It is primarily used in the treatment of schizophrenia and bipolar disorder; other uses include as an add-on treatment in major depressive disorder and obsessive–compulsive disorder (OCD), tic disorders, and irritability associated with autism. Aripiprazole is taken by mouth or via injection into a muscle. A Cochrane review found low-quality evidence of effectiveness in treating schizophrenia.
The dopamine hypothesis of schizophrenia or the dopamine hypothesis of psychosis is a model that attributes the positive symptoms of schizophrenia to a disturbed and hyperactive dopaminergic signal transduction. The model draws evidence from the observation that a large number of antipsychotics have dopamine-receptor antagonistic effects. The theory, however, does not posit dopamine overabundance as a complete explanation for schizophrenia. Rather, the overactivation of D2 receptors, specifically, is one effect of the global chemical synaptic dysregulation observed in this disorder.
Dopamine receptors are a class of G protein-coupled receptors that are prominent in the vertebrate central nervous system (CNS). Dopamine receptors activate different effectors through not only G-protein coupling, but also signaling through different protein interactions. The neurotransmitter dopamine is the primary endogenous ligand for dopamine receptors.
Tetrabenazine is a drug for the symptomatic treatment of hyperkinetic movement disorders. It is sold under the brand names Nitoman and Xenazine among others. On August 15, 2008, the U.S. Food and Drug Administration approved the use of tetrabenazine to treat chorea associated with Huntington's disease. Although other drugs had been used "off label," tetrabenazine was the first approved treatment for Huntington's disease in the U.S. The compound has been known since the 1950s.
Cross-tolerance is a phenomenon that occurs when tolerance to the effects of a certain drug produces tolerance to another drug. It often happens between two drugs with similar functions or effects—for example, acting on the same cell receptor or affecting the transmission of certain neurotransmitters. Cross-tolerance has been observed with pharmaceutical drugs such as anti-anxiety agents and illicit substances, and sometimes the two of them together. Often, a person who uses one drug can be tolerant to a drug that has a completely different function. This phenomenon allows one to become tolerant to a drug that they have never used before.
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A serotonin–norepinephrine–dopamine reuptake inhibitor (SNDRI), also known as a triple reuptake inhibitor (TRI), is a type of drug that acts as a combined reuptake inhibitor of the monoamine neurotransmitters serotonin, norepinephrine, and dopamine. It does this by concomitantly inhibiting the serotonin transporter (SERT), norepinephrine transporter (NET), and dopamine transporter (DAT), respectively. Inhibition of the reuptake of these neurotransmitters increases their extracellular concentrations and, therefore, results in an increase in serotonergic, adrenergic, and dopaminergic neurotransmission. The naturally-occurring and potent SNDRI cocaine is widely used recreationally and often illegally for the euphoric effects it produces.
(–)-Benzofuranylpropylaminopentane is an experimental drug related to selegiline which acts as a monoaminergic activity enhancer (MAE). It is orally active in animals.
Nuciferine is an alkaloid found within the plants Nymphaea caerulea and Nelumbo nucifera.
LY-341495 is a research drug developed by the pharmaceutical company Eli Lilly, which acts as a potent and selective orthosteric antagonist for the group II metabotropic glutamate receptors (mGluR2/3).
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Research into the mental disorder of schizophrenia, involves multiple animal models as a tool, including in the preclinical stage of drug development.
Alstonine is a pentacyclic alkaloid and putative antipsychotic constituent of various plant species including Alstonia boonei, Catharanthus roseus, Picralima nitida, Rauwolfia caffra and Rauwolfia vomitoria. In preclinical studies alstonine attenuates MK-801-induced hyperlocomotion, working memory deficit and social withdrawal. It also possesses anxiolytic-like effects in preclinical studies, attenuates amphetamine-induced lethality and stereotypy as well as apomorphine-induced stereotypy, and attenuates haloperidol-induced catalepsy. These effects appear to be mediated by stimulation of the 5-HT2C receptor. In addition, alstonine, similarly to clozapine, indirectly inhibits the reuptake of glutamate in hippocampal slices. Unlike clozapine however, the effect of which is abolished by the D2 receptor agonist apomorphine, alstonine requires 5-HT2A and 5-HT2C receptors to produce this effect, as it is abolished by antagonists of these receptors. Also unlike clozapine, alstonine lacks pro-convulsant activity in mice.
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The conditioned avoidance response (CAR) test, also known as the active avoidance test, is an animal test used to identify drugs with antipsychotic-like effects. It is most commonly employed as a two-way active avoidance test with rodents. The test assesses the conditioned ability of an animal to avoid an unpleasant stimulus. Drugs that selectively suppress conditioned avoidance responses without affecting escape behavior are considered to have antipsychotic-like activity. Variations of the test, like testing for enhancement of avoidance and escape responses, have also been used to assess other drug effects, like pro-motivational and antidepressant-like effects.