Changes in brain serotonin and 5-hydroxyindolacetic acid levels in the rabbit following tonic immobility.
The effect of tonic immobility on serotonin (5-hydroxytryptamine, 5-HT) and on 5- hydroxyindolacetic acid (5-HIAA) levels in different brain areas has been investigated, following two different schedules of treatment. The massed treatment consisted of a series of consecutive trials up to 15 min, the spaced treatment in 4 series of trials within 24 hours. Massed treatment produced a decrease in 5-HT in the mesencephalon and of 5-HIAA in the pons-medullary area, but similar changes were also elicited in animals treated with the procedure of induction not followed by immobility. The spaced treatment, which resulted in a potentiation of the immobility duration, i.e., sensitization, produced a reduction of 5-HT levels in the mesencephalon and of 5-HT turnover in the striatum. The procedure of the induction per se acts preferentially on 5-HIAA by increasing its levels. In the striatum, which appears selectively responsive to the spaced treatment of immobility, a negative correlation has been found between serotonin levels and immobility duration. Results suggest that elicitation of tonic immobility is associated with reduced levels of 5-HT in the brain.
D000818:Animals; D001923:Brain Chemistry; D003342:Corpus Striatum / Q000032:analysis; D004644:Emotions / Q000502:physiology; D006897:Hydroxyindoleacetic Acid / Q000032:analysis*; D007103:Immobilization; D008297:Male; D008526:Medulla Oblongata / Q000032:analysis; D008636:Mesencephalon / Q000032:analysis; D011149:Pons / Q000032:analysis; D011817:Rabbits; D012149:Restraint, Physical; D012701:Serotonin / Q000032:analysis*
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid