Fimbria-fornix vs selective hippocampal lesions in rats: effects on locomotor activity and spatial learning and memory

The behavioral effects of interrupting the axons that pass in the fimbria and dorsal fornix were compared with the effects of selective removal of the cells that comprise the hippocampus with ibotenic acid. Starting 4.5 months after surgery, lesioned and control rats were (i) trained in both the Morris water maze and the eight-arm radial maze using protocols that placed an emphasis on either working memory (WM) or reference memory (RM) and (ii) tested for locomotor activity in the home cage. In comparison to sham-operated rats, the rats from both lesion groups were impaired in most learning/memory tasks, but there were some interesting differences between the two lesioned groups. When compared to rats with fimbria-fornix lesions (FIFX rats), hippocampal rats (HIPP rats) were slower in learning to swim to a visible platform and showed a greater impairment than FIFX rats in the radial-maze task when the testing procedure required the utilization of RM and WM in a more demanding WM task. In the test of locomotor activity, FIFX and control rats did not differ, but HIPP rats were more active than the rats in both other groups. The pattern of results obtained after a 4.5-month recovery period support the following general conclusions. (1) While there are some similarities in the effects on behavior of interrupting the axons in the fimbria-fornix compared to removing the hippocampus, there are some important differences. (2) From the findings that are available, a possible explanation to account for the difference between FIFX and HIPP rats is that the 4.5-month survival time permitted some recovery in the group of rats with FIFX lesions. (3) While it is well known that the Morris water maze and the radial-arm maze tasks provide useful measures of spatial learning and memory processes, our results suggest that the information provided by the two spatial learning tasks may differ in important respects.

Immunohistochemical and neurochemical correlates of learning deficits in aged rats

This study examined whether cholinergic and monoaminergic dysfunctions in the brain could be related to spatial learning capabilities in 26-month-old, as compared to three-month-old, Long-Evans female rats. Performances were evaluated in the water maze task and used to constitute subgroups with a cluster analysis statistical procedure. In the first experiment (histological approach), the first cluster contained young rats and aged unimpaired rats, the second one aged rats with moderate impairment and the third one aged rats with severe impairment. Aged rats showed a reduced number of choline acetyltransferase- and p75(NTR)-positive neurons in the nucleus basalis magnocellularis, and choline acetyltransferase-positive neurons in the striatum. In the second experiment (neurochemical approach), the three clusters comprised young rats, aged rats with moderate impairment and aged rats with severe impairment. Alterations related to aging consisted of reduced concentration of acetylcholine, norepinephrine and serotonin in the striatum, serotonin in the occipital cortex, dopamine and norepinephrine in the dorsal hippocampus, and norepinephrine in the ventral hippocampus. In the first experiment, there were significant correlations between water maze performance and the number of; (i) choline acetyltransferase- and p75(NTR)-positive neurons in the nucleus basalis magnocellularis; (ii) choline acetyltransferase-positive neurons in the striatum and; (iii) p75(NTR)-positive neurons in the medial septum. In the second experiment, water maze performance was correlated with the concentration of; (i) acetylcholine and serotonin in the striatum; (ii) serotonin and norepinephrine in the dorsal hippocampus; (iii) norepinephrine in the frontoparietal cortex and; (iv) with other functional markers such as the 5-hydroxyindoleacetic acid/serotonin ratio in the striatum, 3,4-dihydroxyphenylacetic acid/dopamine ratio in the dorsal hippocampus, 5-hydroxyindoleacetic acid/serotonin and homovanillic acid/dopamine ratios in the frontoparietal cortex, and 3,4-dihydroxyphenylacetic acid/dopamine ratio in the occipital cortex. The results indicate that cognitive deficits related to aging might involve concomitant alterations of various neurochemical systems in several brain regions such as the striatum, the hippocampus or the cortex. It also seems that these alterations occur in a complex way which, in addition to the loss of cholinergic neurons in the basal forebrain, affects dopaminergic, noradrenergic and serotonergic processes.

"Short-stops" in rats with fimbria-fornix lesions: evidence for change in the mobility gradient

Rats with damage to the hippocampal formation and allied structures are hyperactive in many test situations but the cause of this hyperactivity is not known. Here the activity of control rats and rats with fimbria-fornix lesions is documented in tests of overnight activity. Details of activity are then characterized from video recordings of behavior in an open field. Rats with fimbria-fornix lesions make significantly more stops of shorter duration and thus more individual trips than control rats but they do not differ in the distance traveled on individual trips or in travel speed. It is suggested that the main difference between fimbria-fornix rats and control rats is that when fimbria-fornix rats stop they remain "still" for shorter durations than do control rats. This finding is discussed in relation to a theory of locomotor/exploratory behavior, and in relation to its implications with respect to the performance of fimbria-fornix rats in studies of learning and memory.

Liquid chromatography of polyglycerol fatty esters and fatty ethers on porous graphitic carbon and octadecyl silica by using evaporative light scattering detection and mass spectrometry

A liquid chromatographic method has been developed for the analysis of polyglycerol fatty esters and fatty ethers which are non-ionic surfactants. Two methods were compared using either octadecyl silica or porous graphitic carbon. The octadecyl silica system with a hydroorganic mobile phase enables to compare the hydrophobic behavior of the compounds. The porous graphitic carbon enables the separation of the diastereoisomers. Detection of these non-UV-absorbing compounds was achieved by evaporative light scattering detection. Identification of isomers was performed by mass spectrometry.

Intrastriatal infusions of methoctramine improve memory in cognitively impaired aged rats

Alterations of striatal cholinergic markers may correlate with cognitive impairments in aged rats. M2 muscarinic receptors were found to be presynaptic inhibitory autoreceptors on striatal cholinergic interneurons. The effect of bilateral intrastriatal infusions of the M2 muscarinic receptor antagonist methoctramine was assessed, in cognitively impaired aged (24-26 months) Long-Evans female rats, on memory performances in a water maze. Compared with vehicle infusions, methoctramine injected bilaterally (1 microg/side) in the dorsolateral striatum, significantly improved procedural memory performance while having no effect on spatial working memory. Our results suggest that, in cognitively impaired aged rats, the blockade of M2 muscarinic receptors in the dorsolateral striatum improves procedural memory probably by enhancing the release of acetylcholine.

Impact of solvent physical parameters on the aggregation process of catanionic amphiphiles

One of the most important solvent physical parameters for aggregation is the cohesive energy density (CED), for it gives an idea of the structured state of the solvent. Nevertheless, our studies on the behavior of catanionic amphiphiles in nonaqueous solvents demonstrated that in order to obtain objects the dielectric constant of the solvent was also a critical parameter, as a too high value of the dielectric constant caused the dissociation of the catanionic ion pair, leading to the separation of the two oppositely charged surfactants composing the catanionic amphiphiles, and then more likely to form small objects such as micelles rather than vesicles. In the case of our glucose-derived catanionic surfactants, vesicles could be obtained in pure water, in glycerol/water mixtures, and in water/formamide mixtures up to a certain ratio of formamide. Above a formamide volume fraction of 0.7, only micelles were formed.

Injections of fluid or septal cell suspension grafts into the dentate gyrus of rats induce granule cell degeneration

This study was originally aimed at investigating the effects of intragyral cell suspension grafts which had been enriched in basic fibroblast growth factor (bFGF) before being implanted into the rat hippocampus denervated by aspiration of the septohippocampal pathways. Whether treated with vehicle alone, vehicle + bFGF, cell suspension with or without bFGF, and irrespective of the surgical treatment (sham-operation, lesions or lesions + grafts), we unexpectedly found approximately 80% of the rats to show morphological alterations in the dentate gyrus (20 weeks post-grafting). These alterations consisted of loss of a part of the granule cells; this loss was most often located in the dorsal leaf of the dentate gyrus. Also, in the close vicinity of the degeneration area, we found severe shrinkage of the molecular layer and disappearance of the typical laminae pattern of acetylcholinesterase distribution. These observations confirm previous findings which showed that fluid injections into the dentate gyrus, a widely used technique for intracerebral administration of drugs, trophic factors or neural grafts, may induce undesirable granule cell necrosis.

The effects of vitamin B6 deficiency on the bone marrow of the rat

Bone marrow from adult rats fed a vitamin B6 deficient diet for two weeks was found to have reduced numbers of neutrophils, erythroid cells and small lymphocytes. The numbers of transitional cells were not reduced. Since the small lymphocyte population in the bone marrow consists of B cells and null cells in approximately the same proportion, it was concluded that both cell types were reduced as a result of the deficiency. A complete recovery in the cellularity of the bone marrow was brought about by returning the vitamin B6 deficient animals to a normal diet for four weeks. Other effects of the two-week vitamin B6 deficient diet included a failure to gain weight, a decrease in thymus weight and a reduction in the numbers of white blood cells in the peripheral blood. All of these defects were corrected after the animals had been fed a normal diet for four weeks.

A homeodomain protein selectively expressed in noradrenergic tissue regulates transcription of neurotransmitter biosynthetic genes

In order to characterize the specificity of expression of the neurotransmitter biosynthetic gene dopamine beta-hydroxylase (DBH), the identification of proteins that interact with the DB1 enhancer was initiated. A homeobox-containing cDNA was isolated from a PC12 expression cDNA library screened with the DB1 enhancer. The homeodomain is a member of the paired-like class, and is encoded by several nonidentical cDNAs. The cDNAs contain the same sequence in the homeodomain and 3' coding and noncoding sequences, but diverge in sequence 5' to the homeodomain. This family of homeobox-containing cDNAs is named Arix. Arix mRNA transcripts are found only in noradrenergic, DBH-positive tissues, and in cell lines derived from those tissue. The DB1 enhancer contains two binding sites for the Arix homeodomain, and both sites contribute to basal activity of the DBH promoter. When introduced into tissue culture, Arix regulates the transcriptional activity from the DBH promoter, and also from the promoter of the tyrosine hydroxylase gene, encoding the initial enzyme of the catecholamine biosynthetic pathway. The pattern of expression of the Arix transcripts, the presence of the homeodomain, and the transcriptional regulatory properties suggest that this family of proteins may be involved in the specificity of expression of the catecholamine biosynthetic genes.

SMART recovery for youth: a small, exploratory qualitative study examining the potential of a mutual-aid, peer support addictive behaviour change program for young people

BACKGROUND

SMART (Self-Management and Recovery Training) Recovery is a mutual-aid program informed by cognitive behaviour therapy and motivational interviewing that provides support for a range of addictive behaviours. SMART Recovery has not been adapted to target young people with addictive behaviours despite the potential to overcome important barriers affecting youth engagement in other addiction programs. This study aimed to engage young people and SMART Recovery facilitators in qualitative interviews and focus groups to explore the potential of such a program and gain specific insights for its development.

METHODS

We conducted qualitative interviews and a focus group with five young people (aged between 14 and 24 years) and eight key stakeholders (including seven SMART Recovery facilitators) to obtain recommendations on how best to reach, engage, and support young people with addictive behaviours in a tailored SMART Recovery program. Qualitative data was transcribed and analysed using iterative categorization.

RESULTS

Five key themes were identified when developing and delivering youth-targeted SMART Recovery. [1] 'Discussing personal experiences to promote a shared identity' refers to the benefits of creating a forum where personal stories are used to connect with others and validate one's experiences. [2] 'Flexible and patient approach' emphasises a preference for facilitators to take a more gentle, less direct approach that allows for discussion beyond addictive behaviours. [3] 'Balancing information and skills with the space for discussion' acknowledges that youth want to connect in a variety of ways, beyond discussion of addictive behaviours, and that they wish to lead skill sharing and development. [4] 'Conveying a community for youth through language' highlighted the need to focus on connecting youth and to avoid the use of generic language to engage young people. [5] 'Group logistics and competing demands' refers to the logistical considerations of implementing a group program for youth that takes into account their competing demands and group accessibility.

CONCLUSION

The findings point to considerations for developing youth specific mutual-aid groups, in particular a youth-targeted SMART Recovery program, such as by ensuring the conversation is youth-led and with an informal and flexible approach to guide group discussion.