The effects of potassium and muscle homogenate on proprioceptive responses in crayfish and crab

Abstract

Proprioception of limbs and joints is a basic sensory function throughout most of the animal kingdom. It is important to understand how proprioceptive organs and the associated sensory neurons function with altered environments such as increased potassium ion concentrations ([K]) from diseased states, ionic imbalances, and damaged tissues. These factors can drastically alter neuronal activity. To assess this matter, we used the chordotonal organ in a walking leg of a blue crab (Callinectes sapidus) and the muscle receptor organ of the crayfish (Procambarus clarkii). These organs serve as tractable models for the analysis of proprioception. The preparations can help serve as translational models for these effects, which may be observed in other invertebrate species as well as mammalian species (including humans). When extracellular potassium concentration ([K]) is increased to 20 mM in both preparations, mixed results are observed with activity increasing in some preparations and decreasing in others after mechanical displacement. However, when [K] is increased to 40 mM, activity drastically decreases in all preparations. Additionally, proprioceptor sensory activity declines upon exposure to a diluted muscle homogenate, which contains a host of intracellular constituents. The robust effects of altered [K] on proprioception in these models illuminate the potential detriments on neuronal function in cases of severe tissue damage as well as altered [K].

Rapid adaptation to elevated extracellular potassium in the pyloric circuit of the crab, Cancer borealis

“…In the pyloric circuit, all local synaptic connections are inhibitory (Eisen and Marder, 1982;. Synaptic transmission in the STG is both graded and spike-mediated, meaning that action potentials are not required for inhibitory synapses to function (Graubard et al, 1980;Manor et al, 1997;Nadim et al, 1997 (Malloy et al, 2017).…”

The Effect of CO2, Intracellular pH and Extracellular pH on Mechanosensory Proprioceptor Responses in Crayfish and Crab

“…(Modified figure). 65,66 Low pHo Acute exposure to the bathing media at pH of 5 decreased the PD organ sensitivity for the 2 and 4 second displacements but after an hour at pHo of 5, the sensitivity to the 1, 2 and 4 second displacements was also significantly reduced. The MRO did not decrease in responsiveness as much as the PD organ with the chronic exposure to low pHo, but since there was such a wide variation in responses from preparation to preparation there was no consistent trend in the response to low pHo.…”

The Effect of Calcium Ions on Mechanosensation and Neuronal Activity in Proprioceptive Neurons

“…This ACURE (authentic course-based undergraduate research experiences) [27,30,31,35] approach we have taken with this project builds on the CURE (course-based undergraduate research experiences) concept [36,37]. This provides an exposure to a research experience as a team within a course setting.…”

“…The arrangement the crab chordotonal organ enables for the exploration of the direct effects of agents on the sensory endings, without the effects on muscle fibers, as well as axon excitability [27,28]. Given there is still an active interest in how [Ca 2+ ] o influences the function of nerves as well as understanding the function of SACs, in the vast variety of SAC subtypes, among organisms [29], the crab leg proprioceptive neurons serve as a viable model for such investigations [24][25][26][27][28]30].…”