naloxone and Learning-Disabilities

Advances in the neurochemistry of learning suggest that many endogenous substances modulate learning processes. Endorphins promote or interfere with learning depending on dose (physiologic versus pharmacologic), task (negative versus positive consequences), and learning stage during which the substance is administered. Endorphins cause amnesia for extraneous details of a task (allowing focusing on main events) and prevent extinction of a learned task (even when forgetting might be adaptive). We have summarized endorphin physiology and review studies of endorphins in animal learning. Implications for the study of human attention and learning disorders are presented.

Topics: Animals; Attention; Avoidance Learning; Brain Chemistry; Child; Dose-Response Relationship, Drug; Endorphins; Humans; Learning; Learning Disabilities; Mice; Naloxone; Rats; Rats, Inbred F344; Rats, Inbred Strains; Reward; Terminology as Topic

The contribution of opioid receptors in the nucleus accumbens to contextual and auditory fear conditioning was examined. Impairment in contextual fear conditioning was found when training occurred under accumbal infusions of the opioid receptor agonist morphine in a dose-dependent and receptor specific fashion, only when shock onset coincided with auditory stimulus offset. Contextual fear conditioning was spared, however when the delivery of shock was not signalled by an auditory stimulus, the auditory stimulus was of low intensity (70dB), or an interval (10s or 30s) was interpolated between auditory stimulus offset and shock onset. These results provide evidence that opioid receptors in the nucleus accumbens regulate competition between contextual and discrete auditory stimuli for association formation.

Topics: Acoustic Stimulation; Analgesics, Opioid; Analysis of Variance; Animals; Conditioning, Psychological; Cues; Dose-Response Relationship, Drug; Electroshock; Fear; Freezing Reaction, Cataleptic; Learning Disabilities; Male; Morphine; Naloxone; Narcotic Antagonists; Nucleus Accumbens; Psychoacoustics; Rats; Rats, Wistar; Reaction Time; Receptors, Opioid

The effects of fmol doses of nociceptin/orphanin FQ on scopolamine-induced impairment of learning and/or memory were examined using spontaneous alternation of Y-maze and step-down type passive avoidance tasks. While fmol doses of nociceptin alone had no effect on spontaneous alternation or passive avoidance behavior in normal mice, administration of nociceptin (10 and/or 100 fmol/mouse) 30 min before spontaneous alternation performance or the training session of the passive avoidance task, significantly improved the scopolamine-induced impairment of spontaneous alternation and passive avoidance behavior. This ameliorating effect was not antagonized by nocistatin (0.5 and 5.0 nmol/mouse, i.c.v.), naloxone benzoylhydrazone (2.3, 11.2, and 56.1 micromol/kg, s.c.) or nor-binaltorphimine (4.9 nmol/mouse, i.c.v.). These results indicated that very low doses of nociceptin ameliorate impairments of spontaneous alternation and passive avoidance induced by scopolamine, and suggested that this peptide has bidirectional modulatory effects on learning and memory; impairment at high doses and amelioration at low doses.

Topics: Analgesics, Opioid; Animals; Avoidance Learning; Disease Models, Animal; Dizocilpine Maleate; Learning Disabilities; Male; Maze Learning; Memory Disorders; Mice; Naloxone; Naltrexone; Narcotic Antagonists; Neuroprotective Agents; Nociceptin; Opioid Peptides; Psychomotor Performance; Rats; Scopolamine

Endogenous opioid peptides modulate and regulate processes of central excitability. Furthermore, opioids are thought to interfere with processes of learning and memory storage. In order to study the effects of endogenous opioids on both processes we injected in the course of development of pentylenetetrazol kindling the opiate receptor antagonist naloxone, and tested the animals afterwards in a shuttle-box task. It was found that naloxone pretreatment had dissociative effects. There was no effect on seizure outcome, whereas the learning deficit was ameliorated in the kindled group. The data suggest that endogenous opioid peptides contribute to the learning deficit found in pentylenetetrazol-kindled rats.

Topics: Animals; Avoidance Learning; Dose-Response Relationship, Drug; Kindling, Neurologic; Learning Disabilities; Male; Naloxone; Pentylenetetrazole; Rats; Rats, Wistar; Seizures; Sodium Chloride

Acute exposure of rats to microwaves (12.6 chr, 2375 MHz, power density 1 mW/cm2) induced the retrograde amnesia. It was show the role of opioidergic, benzodiazepine, GABAergic and cholinergic components in the amnesic effects of microwaves. Piracetam (100 mg/kg, i. p.) and oxiracetam (10 mg/kg, i. p.) prevented the negative effects of microwaves on memory processes.

Topics: Animals; Learning Disabilities; Male; Memory Disorders; Microwaves; Naloxone; Piracetam; Psychotropic Drugs; Pyrrolidines; Radioligand Assay; Rats; Rats, Wistar; Receptors, Cholinergic; Receptors, GABA-A; Receptors, Opioid