Tempering aversive/traumatic memories with cannabinoids: a review of evidence from animal and human studies.

RATIONALE: Aversive learning and memory are essential to cope with dangerous and stressful stimuli present in an ever-changing environment. When this process is dysfunctional, however, it is associated with posttraumatic stress disorder (PTSD). The endocannabinoid (eCB) system has been implicated in synaptic plasticity associated with physiological and pathological aversive learning and memory. OBJECTIVE AND METHODS: The objective of this study was to review and discuss evidence on how and where in the brain genetic or pharmacological interventions targeting the eCB system would attenuate aversive/traumatic memories through extinction facilitation in laboratory animals and humans. The effect size of the experimental intervention under investigation was also calculated. RESULTS: Currently available data indicate that direct or indirect activation of cannabinoid type-1 (CB1) receptor facilitates the extinction of aversive/traumatic memories. Activating CB1 receptors around the formation of aversive/traumatic memories or their reminders can potentiate their subsequent extinction. In most cases, the effect size has been large (Cohen's d ≥ 1.0). The brain areas responsible for the abovementioned effects include the medial prefrontal cortex, amygdala, and/or hippocampus. The potential role of cannabinoid type-2 (CB2) receptors in extinction learning is now under investigation. CONCLUSION: Drugs augmenting the brain eCB activity can temper the impact of aversive/traumatic experiences by diverse mechanisms depending on the moment of their administration. Considering the pivotal role the extinction process plays in PTSD, the therapeutic potential of these drugs is evident. The sparse number of clinical trials testing these compounds in stress-related disorders is a gap in the literature that needs to be addressed.

Efficacy and security of ivermectin given orally to rats naturally infected with Syphacia spp., Giardia spp. and Hymenolepis nana.

The results of this study show that the oral administration of ivermectin (48 mg/L) repeatedly for 72 h used in accordance with the present protocol is a safe and highly effective treatment for Giardia spp. and Hymenolepis nana in laboratory rat colonies. The drug can be easily and safely administered using drinking water. This simple regimen should control pinworm infection (Syphacia muris), a problem that can be endemic in laboratory colonies. Experiments using healthy animals are likely to generate more consistent results, thereby requiring a reduced number of animals per group.

Protein synthesis in dorsal hippocampus supports the drug tolerance induced by prior elevated plus-maze experience.

Tolerance to the anxiolytic-like effect of drugs may develop because of a memory derived from prior experience in certain apparatuses such as the elevated plus-maze (EPM). Activity in basolateral amygdala was shown to be required for consolidating this knowledge. The dorsal hippocampus (DH) is also implicated in long-term memory consolidation, a process relying on new protein synthesis. It is unknown, however, whether the DH protein synthesis disruption would prevent the phenomenon rendering animals unresponsive to benzodiazepines in the EPM retest. To address this, we bilaterally infused the protein synthesis inhibitor anisomycin (ANI) into the rat DH 0, 3 or 6 h after, or 15 min before, the EPM test. DH infusion of ANI (80 µg) around the time of EPM testing preserved the anxiolysis of the midazolam (MDZ; 0.5 mg/kg, i.p.) in rats retested in the EPM 24 h later, suggesting that information consolidated by DH protein synthesis impacts on the subsequent animal's responsiveness to this drug. To examine whether impaired memory acquisition could also contribute to the prevention of MDZ tolerance seen in EPM-experienced animals infused with ANI before testing, the EPM retest was performed 3 h after testing to coincide with the temporal window in which short-term memory remains, for the reason that this process does not require protein synthesis for its formation. The pretest DH anisomycin infusion's ability to prevent the MDZ tolerance on retesting was now missing. This result confirms a specific action of the ANI on memory consolidation. We also found that rats express further avoidance to open-arms in the EPM retest. However, neither pretest nor posttest DH ANI infusion interfered with this pattern of results exhibited by EPM-experienced rats.

Activity in prelimbic cortex is required for adjusting the anxiety response level during the elevated plus-maze retest.

The prelimbic (PL) subregion of medial prefrontal cortex has been implicated in anxiety regulation. It is unknown, however, whether PL cortex also serves to fine-tuning the level of anxiety-related behavior exhibited on the next exposure to the same potentially threatening situation. To address this, we infused cobalt (1.0 mM) to temporarily inactivate the PL cortex during testing, post-testing or retesting in the elevated plus-maze (EPM). This protocol was chosen because it allowed us to concurrently investigate anxiety and the process of aversive learning and memory. PL cortex inactivation during the EPM testing increased the exploration of open-arms, substantiating its role in anxiety. PL cortex inactivation during the EPM retesting counteracted the further avoidance to open-arms exhibited by rats. Interestingly, as evidenced by min-by-min analysis, the cobalt-treated group behaved on EPM retesting as did the vehicle-treated group on EPM testing. This result may imply that activity in PL cortex is necessary for retrieving previously learned information that adjusts the anxiety response level on EPM retesting. Alternatively, a simple reduction in anxiety could explain the cobalt-induced increase in retest open-arms exploration. Neither test nor post-test PL cortex inactivation affected the further avoidance to open-arms observed on EPM retesting. To extend the investigation of PL cortex role in the regulation of open-arms avoidance, we infused other drugs prior to testing or retesting in the EPM. Antagonism of PL cortex adrenergic beta-1 receptors with atenolol (10 nmol), cholinergic muscarinic receptors with scopolamine (20 nmol) or glutamatergic N-methyl-d-aspartic acid (NMDA) receptors with AP5 (6.0 nmol) interfered with the level of open-arms exploration on testing, but not on retesting.

Aversive learning as a mechanism for lack of repeated anxiolytic-like effect in the elevated plus-maze.

Rodents re-exposed to the elevated plus-maze no longer respond to anxiolytic-like drugs, such as benzodiazepines. This phenomenon is thought to be due to retrieval of aversive learning associated with the initial exploration of this potentially dangerous environment Based on this assumption, one might expect the maintenance of the drug's anxiolytic-like effect in rodents already experienced in the elevated plus-maze if the acquisition and/or consolidation of this learning were impaired. Using male Wistar rats, we investigated whether the systemic administration of propranolol, at putative learning-impairing doses, prior to or immediately after the first (Trial 1) elevated plus-maze exposure would retain the midazolam anxiolytic-like effect on the second (Trial 2) exposure to this apparatus. There was an anxiolytic-like effect, characterized by an increase in the open-arms exploration, in response to 0.25 mg/kg of midazolam on Trial 2 only in rats administered with 20 mg/kg of propranolol before Trial 1. Although propranolol had a dose-dependent and behaviorally-selective anti-anxiety effect (significant at 20 mg/kg) on Trial 1, further minute-by-minute analysis confirmed the propranolol-induced learning acquisition deficit in this group on Trial 2. The knowledge of the environment actually contributes to the unresponsiveness to anxiolytic-like drugs observed in rats re-exposed to the elevated plus-maze.

A ganglioside-specific sialyltransferase localizes to axons and non-Golgi structures in neurons.

To investigate the tissue distribution and subcellular localization of ST3GalV (CMP-NeuAc:lactosylceramide alpha2,3 sialyltransferase/GM3 synthase) in the adult mouse, we generated two antisera against mouse ST3GalV that were designated CS2 (directed against amino acids K227-I272) and CS14 (directed against amino acids D308-H359). We previously reported that CS2 antiserum stains medial and trans-Golgi cisternae in all cell types investigated. In neural tissue, however, CS14 antiserum reveals a subpopulation of ST3GalV with a subcellular distribution complementary to CS2 antiserum. CS14 antiserum strongly stains axons in cortical, cerebellar, brainstem, and spinal cord tissue sections. The subcellular localization of neuronal ST3GalV is maintained in primary cultures of rat hippocampal neurons and in PC12 cells. In PC12 cells, ST3GalV localization evolves during NGF-induced differentiation such that a pool of enzyme leaves the Golgi for a distal compartment in conjunction with neurite outgrowth. In PC12 cells transfected with an epitope-tagged form of ST3GalV, staining for the epitope tag coincides with expression of endogenous enzyme. The non-Golgi pool of ST3GalV does not colocalize with markers for the trans-Golgi network, endosome, or synaptic vesicles, nor is it detected on the cell surface. Distinct subpopulations of ST3GalV imply that ganglioside synthesis can occur outside of the Golgi or, alternatively, that a portion of the total ST3GalV pool subserves a nonenzymatic function. Significantly fewer transfected cells were found in PC12 cultures treated with plasmid encoding ST3GalV than in cultures treated with control plasmid, indicating that the expression of ST3GalV in excess of endogenous levels results in either cell death or a decreased rate of cell division.

Molecular identification, tissue distribution and subcellular localization of mST3GalV/GM3 synthase.

A molecular screen for a mouse homologue of a Drosophila carbohydrate binding protein, called Gliolectin, yielded a cDNA encoding mST3GalV/GM3 synthase (CMP-NeuAc: lactosylceramide alpha2, 3-sialyltransferase). By in situ hybridization and immunohistochemistry, mST3GalV exhibits differential expression in neural and non-neural tissues. Although expressed by all neurons in the central nervous system, neuronal populations that contribute their axons to myelinated efferent projections, such as cerebellar Purkinje cells and spinal motorneurons, demonstrate the highest ST3GalV expression. When stained with anti-mST3GalV antiserum (designated CS2), subpopulations of neurons display an elaborate Golgi apparatus, frequently extending into one or more dendritic processes. The extended spatial distribution of the neuronal Golgi apparatus, particularly in spinal motorneurons, allowed the confocal immunohistochemical colocalization of mST3GalV with markers for medial/trans-Golgi but not the cis-Golgi or trans-Golgi network, consistent with previous observations suggesting that ganglioside glycosyltransferases are enriched in late Golgi compartments. Among non-neural tissues, liver and testes demonstrate cell-type specific CS2 staining. In liver, endothelial cells lining a ring of sinusoids, concentric with the central vein, express mST3GalV. Kupffer cells are also stained with CS2 antiserum but hepatocyte expression is undetectable. In the seminiferous tubules of the testes, ST3GalV is found in somatic (Leydig, Sertoli) and early germline cells (spermatogonia and primary spermatocytes); the epididymal epithelium exhibits intense ST3GalV expression. Since GM3 is a precursor for the synthesis of a- and b-series gangliosides, the range of mST3GalV/GM3 synthase expression among various cell populations indicates that certain cell types possess greater reliance on ganglioside function than others.

Biomechanical performance of orthopedic gloves.

The purpose of this study was to compare the biomechanical performance of commercially available orthopedic gloves to that of a single surgical glove, as well as a double glove system. The orthopedic gloves were found to be thicker than the single surgical glove. This increased thickness of the orthopedic glove was associated with a greater resistance to glove puncture. The thickest orthopedic gloves also had reduced tactile sensitivity when compared to the single surgical glove. In addition, the glove donning forces and glove hydration rates varied considerably. These latter biomechanical performance parameters were not significantly related to glove thickness. The double glove systems tested in this study had similar performance characteristics in regard to many of the orthopedic gloves. The glove donning forces for the double glove systems were the lowest of the gloves tested. In addition, the double glove systems displayed the greatest resistance to glove hydration of the gloves tested. Their performance in the glove hydration tests and the force required to don the double glove systems were much more desirable than any of the orthopedic gloves. The results of this study indicate that the double glove systems may provide a desirable alternative to the use of the single orthopedic gloves.