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PubMedDate not supplied

The effects of structure-conformation modifications of melanotropin analogs on learning and memory: D-amino acid substituted linear and cyclic analogs.

Alpha-MSH has a wide variety of putative biological activities in addition to its classical melanocyte dispersing activity. Since each of these activities appears to be mediated by a discrete receptor, this peptide is an excellent candidate for exploring conformational restrictions which determine the chemical-physical basis for hormone action on specific activities. Experiments One and Two evaluated several cyclic and linear analogs of alpha-MSH on retrieval of memory during the reactivation of memory for a passive avoidance response following hypothermia-induced amnesia. Three of the cyclic analogs appear to have enhanced the peptide's ability to serve as a reactivation agent. One of the linear Nle4,D-Phe7 analogs antagonized whereas three others enhanced reactivation. The D-Phe7 substitution in cyclic analogs did not affect reactivation. Another group of animals were trained on a step-through passive avoidance task and tested 25 days later. The cyclic analog enhanced memory whereas the D-Phe7 analog and alpha-MSH had no effect. Finally, two analogs were tested on a black-white discrimination. Although the cyclic analog had no effect on either acquisition or reversal of this learning, the Nle4,D-Phe7 analog significantly impaired reversal learning. The results from these preliminary studies suggest that structural modifications of alpha-MSH do alter its potency and pattern of actions in learning and memory situations.

Amino Acid Sequence↗
PubMed1988

A comparative study of visuospatial memory and learning in Alzheimer-type dementia and Parkinson's disease.

Groups of patients with dementia of Alzheimer type (DAT) and idiopathic Parkinson's disease, together with age and IQ-matched normal controls, were compared on several computerized tests of visuospatial memory and learning. Two different groups of parkinsonian patients were studied: (1) a newly diagnosed group, early in the course of the disease, not receiving medication (NMED) PD) and (2) a group later in the course of the disease, receiving medication (MED PD). The DAT and MED PD group were significantly impaired in both spatial and visual pattern recognition memory. The DAT group exhibited a delay-dependent deficit (over 0-16 s) in a delayed matching-to-sample procedure, but were not impaired at simultaneous-matching-to-sample. By contrast, the MED PD group showed delay-independent deficits in the delayed matching-to-sample test and both the MED PD and the NMED PD group were also significantly impaired in simultaneous matching. In a form of delayed response test, the subjects were required first to memorize and then to learn the locations of several abstract visual stimuli which varied progressively in number from 1 to 8. The DAT group were severely impaired in this conditional associative learning task. A significant proportion of patients, but none of the controls, in the NMED and MED PD group also failed the test at the levels of 6 or 8 items. There was a significant correlation between the performance on the first trial, memory score in the delayed response task and indices of clinical disability and disease duration in the patients with Parkinson's disease. The results are discussed in terms of the utility of the comparison between DAT and PD in characterizing the nature of the cognitive deficits in these conditions and their relation to those findings from animal neuropsychology which use comparable paradigms.

Alzheimer Disease↗
PubMed2003

Role of the mesotelencephalic dopamine system in learning and memory processes in the rat.

The effects of lesioning the ventral tegmental area or substantia nigra pars reticulata by means of bilateral microinjections of two doses of kainic acid (50 ng/250 nl and 100 ng/500 nl) or 6-hydroxydopamine (8 microg/4 microl) were investigated to clarify the role of the mesotelencephalic dopamine system in learning and memory processes. Our findings suggest that ventral tegmental area and substantia nigra dopaminergic neurons play an important role in retention of both short-term memory, tested in the Y-maze task and long-term memory evaluated with the multi-trial passive avoidance test, without affecting memory acquisition. As compared to short-term memory, long-term memory is more susceptible to the decreased dopamine level in nervous structures involved in processing and storage of information.

Animals↗
PubMed1984

The effects of dieldrin and chlordimeform on learning and memory in the cockroach, Periplaneta americana: a study in behavioral toxicology.

A one-session T-maze training procedure for cockroaches in which animals were trained to turn right or left to avoid a shock was utilized to investigate the effects of dieldrin and chlordimeform (two neurotoxic pesticides) on learning and memory. These animals were trained and then tested for retention 5 h later. Three behavioral measures were recorded: choice behavior or direction turned, the time taken to proceed down the runway (runway time), and the time taken to proceed from the runway to either choice arm (choice point time). In control animals the number of correct choices, the runway time, and the choice point time increased with succeeding trials during training. Furthermore, control animals showed retention of correct choice behavior from training to testing. A nontoxic dose (no overt behavioral signs) of dieldrin was injected 2 h before training or 15 min after training. Pretraining injections of dieldrin eliminated correct-choice learning but did not alter the increase with training in runway or choice point times. Posttraining dieldrin administration did not interfere with retention of correct-choice behavior upon testing. These findings indicate that dieldrin induces behavioral alterations in a low acute dose and that detrimental effects are more likely with more complex behavior. Furthermore, behavioral disruption is more likely the closer exposure is to the initial learning of a task. Nontoxic doses of chlordimeform injected 1 h before training eliminated correct-choice learning and facilitated an increase in runway times during training.

Amidines↗
PubMedDate not supplied

Effect of vasopressin analog [d(CH2)1(5),Tyr(Me)2]AVP on learning and memory in rats chronically treated with ethanol.

The effect of single 2 micrograms dose of vasopressin (AVP) and analog [d(CH2)1(5),Tyr(Me)2]AVP on processes of retrieval, acquisition and consolidation of conditioned reflexes in rats chronically alcoholized was studied. Long term (9 weeks) ethanol intoxication profoundly impaired learning and memory processes in all tests used. The AVP analog [d(CH2)1(5), Tyr(Me)2]AVP facilitated retrieval of passive avoidance, improved consolidation of active avoidance of rats previously treated with alcohol, but did not affect the acquisition of active avoidance. [d(CH2)1(5), Tyr(Me)2]AVP did not affect the motor and exploratory activity of rats in open field.

Animals↗
PubMed1985

Involvement of the amygdala in learning and memory: a critical review, with emphasis on anatomical relations.

The amygdala has been attributed with a considerable number of very diverse functions. Its involvement in learning and memory, though, has found increased attention. Following a short description of the connections of the amygdala and its critical neurotransmitters, studies are reviewed here in which the amygdala's activity was manipulated or observed by different methods (lesions, electrical brain stimulation, neurochemical intra-amygdaloid injections, single-unit recordings). Some of the major conclusions resulting from this data analysis indicate an advantage in performing subtotal amygdaloid lesions over an amygdalectomy, a point of view that is especially supported by the heterogeneous anatomical connections of different amygdaloid nuclei. Thereafter, an evaluation is made of different tasks with respect to their discriminative sensitivity to amygdaloid manipulations. Some species-specific differences in performing certain tasks after amygdaloid injuries are discussed in relation to the different expansion of amygdalo-cortical connections in higher and less highly encephalized species. Finally, some general assumptions are made on the specific role of each of the amygdaloid nuclei during the mnemonic processes attributed to the amygdala. It is concluded that emotionally significant information is encoded and can be retrieved on the basis of the structures and connections of the basolateral limbic circuit.

Amygdala↗
PubMed1994

Involvement of amino acids, opioids, nitric oxide, and NMDA receptors in learning and memory consolidation in crickets.

The effect of injections of selected amino acids and of N-methyl-D-aspartate (NMDA); morphine; and NMDA, nitric oxide (NO), and opioid inhibitors given before a maze-learning was investigated. Thirsty crickets (Pteronemobius sp) were trained to turn only to one side of a symmetrical Y-shaped maze using reinforcements with water. The insects retained the learned task 24 h later. N2 anoxia applied immediately after training produced retrograde amnesia. Injections of alanine (Ala), arginine (Arg), glutamine (Gln), morphine, or NMDA prior to training blocked the amnesic action of anoxia. Naloxone, an opioid antagonist, blocked long-term memory formation, but not learning, whereas hemoglobin or 2-amino-5-phosphonovaleric acid (APV), NO and NMDA antagonists respectively, blocked both. The antiamnesic effect of Morphine and Arg, but not that of Ala or NMDA was blocked by naloxone. The results suggest involvement of NMDA receptors and NO and thus of long-term potentiation phenomena in learning and in memory consolidation, whereas other neuromodulatory systems related to Arg, and opiate receptors, are only involved in memory consolidation.

2-Amino-5-phosphonovalerate↗
PubMed2005

Crystallization and preliminary X-ray diffraction analysis of calexcitin from Loligo pealei: a neuronal protein implicated in learning and memory.

The neuronal protein calexcitin from the long-finned squid Loligo pealei has been expressed in Escherichia coli and purified to homogeneity. Calexcitin is a 22 kDa calcium-binding protein that becomes up-regulated in invertebrates following Pavlovian conditioning and is likely to be involved in signal transduction events associated with learning and memory. Recombinant squid calexcitin has been crystallized using the hanging-drop vapour-diffusion technique in the orthorhombic space group P2(1)2(1)2(1). The unit-cell parameters of a = 46.6, b = 69.2, c = 134.8 A suggest that the crystals contain two monomers per asymmetric unit and have a solvent content of 49%. This crystal form diffracts X-rays to at least 1.8 A resolution and yields data of high quality using synchrotron radiation.

Calcium↗
PubMed1996

Verbal learning and memory in children with fetal alcohol syndrome.

Children with fetal alcohol syndrome (FAS) were administered the California Verbal Learning Test-Children's Version, a word list learning task that assesses immediate and delayed recall and recognition memory. When compared with matched control children, the children with FAS had difficulty learning and recalling the words after a delay period and tended to make an increased number of intrusion and perseverative errors. In addition, they had difficulty discriminating target words from distracter words and made more false-positive errors on recognition testing. Some of these deficits persisted even when mental age was controlled. The results suggest that children with FAS have profound verbal learning and memory deficits, and that some of these deficits cannot be accounted for even when mental age is considered. Furthermore, the results are consistent with deficits in encoding verbal information and impairment in response inhibition capabilities.

Adolescent↗