Introduction
Binge drinking among adolescents is an ongoing public health concern. Although binge drinking can also be harmful to adults, the adolescent population is more susceptible to aberrant neurological changes as their brains are still undergoing significant development. The waddles (wdl) mouse is characterized by a namesake waddling gait due to a homozygous mutation of the Car8 gene. Carbonic anhydrase type 8 (CAR8) controls the intracellular release of calcium (Ca²⁺) from internal stores. Both models display a similar cerebellar based ataxia which is why they were chosen for comparison.
Methods
Groups of pre-adolescent post-natal day (PND 26) and adolescent (PND 34) rats underwent a series of behavioral tests designed to assess memory, anxiety regulation, and motor function. Subjects were first exposed to either ethanol or plain air through a vapour chamber apparatus for five consecutive days (two hours per day). Rota-rod testing was conducted to characterize the wdl mutation and ethanol treatment effects on motor output. Acute cerebellar slices from wdl mice were subsequently utilized for fluorescent calcium imaging experiments. Western blotting was used for protein quantification in the homogenized cerebella of both models.
Results
Behavioral testing using the rota-rod, cage-hang, novel object recognition, light-dark box, and elevated plus maze apparatuses showed significantly decreased object memory and measures of anxiety-related behaviors in ethanol treated subjects. Western blotting indicated elevated levels of proinflammatory/proapoptotic proteins in the cerebella of ethanol treated and wdl animals. Younger homozygous wdl mice outperformed their older cohorts on the rota-rod. Heterozygotes, which were thought to be free of motor impairment, displayed motor learning deficiencies. Calcium imaging revealed significant attenuation of cerebellar granule cell somatic Ca²⁺ signaling in homozygous mice.
Conclusion
Differences on anxiety tests indicate a failure of behavioral inhibition in the ethanol treated group. There are also impairments to motor coordination and object memory, which involve the cerebellar and hippocampal brain regions, respectively. When taken together with work on the wdl mouse, these findings suggest disruptions in cerebellar circuitry hampering proper neuronal communication have drastic consequences for behavioral output of the cerebellum
