Licorice-Induced Pseudohyperaldosteronism Presenting as Seizure with Posterior Reversible Encephalopathy Syndrome: A Case Report.

Constantly adjusting behaviors to the environment is a critical skill for animals’ survival. Flexibly generating different behaviors or tuning a movement to a changing environment is mediated by the multifunctionality of the nervous system, which can occur at the circuitry level, the synaptic level and at the individual neuronal level (; ; ; ). One challenge for adaptation to a changing environment is that the organism needs to integrate ongoing sensory inputs from the environment with motor outputs. Studies have shown that individual neurons can have multiple roles as they integrate sensory signals, including proprioceptive and exteroceptive inputs, to modify behaviors. For example, in zebrafish, proprioceptive neurons that signal the stretching of the spinal cord were found to have direct inhibitory connections to pattern-generating interneurons, providing feedback during movement (). In the guinea pig enteric nervous system, some identified interneurons and motor neurons were found to be sensitive to mechanical stretch of the ganglia (). Multiaction neurons can also play important roles in maintaining internal homeostasis by combining sensory and secretory roles (). ’s feeding circuitry is a good model to study the multifunctionality of individual neurons, as its nervous system is experimentally tractable and capable of producing multiple motor outputs. Over the years, the neural circuitry and the biomechanics underlying different feeding behaviors have been studied in detail, with many neurons’ functions, connections and innervations characterized (see references in ; ; ). A particular set of neurons in the feeding circuit of , designated as B4 and B5 (), are electrically coupled interneurons that have an important function in rejection. During rejection, B4/B5 fire at a high frequency (~ 20 Hz to > 50 Hz; ; ; ; ) for a long duration (~ 2 s to > 5 s; ), imposing strong inhibition on the follower motor neurons. In , it was found that intense activation of B4/B5 delays the contraction of the I3 muscle, preventing the lumen of the jaws from contracting and closing the opened radula during the retraction phase of egestion, which would draw inedible food back into the buccal cavity, preventing rejection. Thus B4/B5 serve an important neuromechanical role in generating effective egestive behavior. In contrast, their functional role during ingestive behaviors is unclear. During swallowing, B4/B5 actively fire action potentials at a lower frequency (< 30 Hz; ; ; ) for a relatively shorter time (~ 2 – 3 s; , ). The duration and initial firing frequency of B4/B5 increase in response to increased mechanical load during swallowing (). Do B4/B5 have a different functional role in ingestive behavior?