Cholinergic deafferentation of the hippocampus causes non-temporally graded retrograde amnesia in an odor discrimination task

Retrograde Axonal Transport of Neurotrophins in Basal Forebrain Cholinergic Neurons

Axonal transport is key for the survival and function of all neurons. This process is especially important in basal forebrain cholinergic neurons due to their extremely long and diffuse axonal projections. These neurons are critical for learning and memory and degenerate rapidly in age-related neurodegenerative disorders like Alzheimer's and Parkinson's disease. The vulnerability of these neurons to age-related neurodegeneration may be partially attributed to their reliance on retrograde axonal transport for neurotrophic support. Unfortunately, little is known about the molecular biology underlying the retrograde transport dynamics of these neurons due to the difficulty associated with their maintenance in vitro. Here, we outline a protocol for culturing primary rodent basal forebrain cholinergic neurons in microfluidic chambers, devices designed specifically for the study of axonal transport in vitro. We outline protocols for labeling neurotrophins and tracking neurotrophin transport in these neurons. Our protocols can also be used to study axonal transport in other types of primary neurons such as cortical and hippocampal neurons.

Specific Phospholipid Modulation by Muscarinic Signaling in a Rat Lesion Model of Alzheimer's Disease

Alzheimer’s disease (AD) represents the most common cause of dementia worldwide and has been consistently associated with the loss of basal forebrain cholinergic neurons (BFCNs) leading to impaired cholinergic neurotransmission, aberrant synaptic function, and altered structural lipid metabolism. In this sense, membrane phospholipids (PLs) can be used for de novo synthesis of choline (Ch) for the further obtaining of acetylcholine (ACh) when its availability is compromised. Specific lipid species involved in the metabolism of Ch have been identified as possible biomarkers of phenoconversion to AD. Using a rat model of BFCN lesion, we have evaluated the lipid composition and muscarinic signaling in brain areas related to cognitive processes. The loss of BFCN resulted in alterations of varied lipid species related to Ch metabolism at nucleus basalis magnocellularis (NMB) and cortical projection areas. The activity of muscarinic receptors (mAChR) was decreased in the NMB and increased in the hippocampus according to the subcellular distribution of M₁/M₂ mAChR which could explain the learning and memory impairment reported in this AD rat model. These results suggest that the modulation of specific lipid metabolic routes could represent an alternative therapeutic strategy to potentiate cholinergic neurotransmission and preserve cell membrane integrity in AD.

Cholinergic neurodegeneration in Alzheimer disease mouse models

Cholinergic signaling is critical for cognitive function. The basal forebrain is the major cholinergic output of the central nervous system. Degeneration of basal forebrain cholinergic neurons is a hallmark of Alzheimer's disease (AD). Mouse models are invaluable tools in disease research and have been used to study AD for over 25 years. However, animal models of AD vary greatly with respect to the degree of cholinergic degeneration observed. The following review will outline the most influential animal models of AD with an emphasis on the basal forebrain cholinergic system.

The structure of arm and hand movements in a spontaneous and food rewarded on-line string-pulling task by the mouse

Arm and hand use by the mouse have been studied in a variety of tasks in order to understand the structure of skilled movements and motor learning, the anatomy and function of neural pathways, and to develop animal models of neurological conditions. The present study describes string-pulling by the mouse, a behavior in which a mouse uses hand-over-hand movements to pull down a string that hangs from the top of a test cage. Mice both spontaneously string-pull and also string-pull to obtain cashew nuts tied to the end of the string as food reward. To string-pull, mice sat upright and tracked the string with their nose and then made hand-over-hand movements to reel in the string. A string-pull movement consists of four arm movements (Advance to make purchase, Pull, Push to draw the string down and Lift to return the hand for the next Advance) and four hand movements (Collect to aim the hand, Overgrasp to position the hand, and Grasp to make purchase, and Release). The kinematic profiles of the string-pull movement are distinctive with each hand making similar movements at a rate of 4 cycles per second and with the Lift and Advance movements occurring at a higher speed than Pull and Push movements. The results are discussed in relation to the antecedent repertoire of mouse behavior that lends itself to string-pulling, with respect to the utility of using string-pulling to investigate motor systems and adapting string-pulling to model neurological conditions in mice.

Voluntary physical exercise protects against behavioral and endocrine reactivity to social and environmental stressors in the prairie vole

Physical activity can combat detrimental effects of stress. The current study examined the potential protective effects of exercise against a combination of social isolation and chronic mild stress (CMS) in a prairie vole model. Female voles were isolated for 4 weeks, with the addition of CMS during the final 2 weeks. Half of the voles were allowed access to a running wheel during this final 2 weeks, while the other half remained sedentary. Animals underwent behavioral tests to assess depressive- and anxiety-behaviors. In a subset of animals, plasma was collected 10 minutes after behavioral testing for corticosterone analysis. In a separate subset, brains were collected 2 hours after behavioral testing for cFos analysis in the paraventricular nucleus (PVN). Voles in the exercise group displayed significantly lower depressive- and anxiety-behaviors, and displayed significantly lower corticosterone levels, compared to animals in the sedentary group. There was no difference in PVN cFos activity between groups. Interestingly, animals that moderately exercised displayed lower levels of depressive-behavior and attenuated corticosterone reactivity compared to animals in the low and high activity subgroups. These findings suggest that physical activity can protect against a combination of social and environmental stressors.

Otolith dysfunction alters exploratory movement in mice

The organization of rodent exploratory behavior appears to depend on self-movement cue processing. As of yet, however, no studies have directly examined the vestibular system's contribution to the organization of exploratory movement. The current study sequentially segmented open field behavior into progressions and stops in order to characterize differences in movement organization between control and otoconia-deficient tilted mice under conditions with and without access to visual cues. Under completely dark conditions, tilted mice exhibited similar distance traveled and stop times overall, but had significantly more circuitous progressions, larger changes in heading between progressions, and less stable clustering of home bases, relative to control mice. In light conditions, control and tilted mice were similar on all measures except for the change in heading between progressions. This pattern of results is consistent with otoconia-deficient tilted mice using visual cues to compensate for impaired self-movement cue processing. This work provides the first empirical evidence that signals from the otolithic organs mediate the organization of exploratory behavior, based on a novel assessment of spatial orientation.