Resumen de Modifications in the distribution of met-enkephalin in the pons of the cat, following the intravenous administration of clonidine: An immunocytochemical experimental study

J. Vazquez, Juan Muñoz Madrid, J.C. García

• The distribution of met-enkephalin in the cat and its modifications following the stimulation by intravenous clonidine , was studied with indirect immunocytochemical techniques. We observed a decrease in the immunoreactivity of met-enkephalin following the administration of clonidine, relative to the controls, in the following structures: locus coeruleus, nucleus cuneformis, formatio reticularis, nucleus gigantocellularis, nucleus reticularis lateralis, nucleus reticularis, nucleus reticularis parvocellularis, nucleus sensorius superior n. trigemini, nucleus raphes, substantia grisea periventricularis, nucleus eminentiae teretis, colliculus inferior, nucleus motorius n. trigemini, nucleus tracto spinalis n. trigemini, tractus spinalis n.

  trigemini and nucleus tracto mesencephalici n. trigemini.

  These experimental observations link the immunoreactivity changes to the structures that are associated with the direct action of clonidine and conclude that the pars metencephalinergicus of the efferent pontine pathway of pain is in morpho-functional relationship with the analgesia produced by clonidine; an analgesic of an endogenous opiate character.