Periaqueductal gray neurons send descending axons into various regions of the medulla releasing serotonin.
a. true
b. false

True

Explanation:

Periaqueductal gray matter is found in the middle portion of brain.  When this grey matter is stimulated it activates neurons that releases enkephalin. Enkephalin further direct the stimulation to the raphe nuclei  with in the brain stem that releases serotonin. In this process, the ascending and descending axons are released  from  

a)subcortical nuclei

b)spinal trigeminal nuclei  

c)the spinal cord

Hence, the given statement is true

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