HISTOLOGY AND HISTOPATHOLOGY

Cellular and Molecular Biology



Modifications in the distribution of met-enkephalin in the cat spinal cord after administration of clonidine. An immunocytochemical study

J. Vázquez1, R. Coveñas2, M. Muñoz3, J.A. García3 and A. Victoria4

1Department of Morphological Sciences, School of Medicine, University of Sevilla, Sevilla, 2Department of Cell Biology and Pathology, School of Medicine, University of Salamanca, Salamanca, 3Service of Pediatry, Children's Hospital, Sevilla and 4Department of Morphological Sciences, School of Medicine, University of Valencia, Valencia, Spain

Offprint requests to: Prof. Dr. José Vázquez, Departamento de Ciencias Morfológicas, Facultad de Medicina, Universidad de Sevilla, Avda. Sánchez Pizjuan s/n, 41009-Sevilla, Spain

 

Summary. We have studied the modifications in the distribution of methionine-enkephalin in the cat spinal cord after intravenous or intrathecal administration of clonidine by using an immunocytochemical technique. In animals not treated with the substance, a very high density of immunoreactive fibers was found in layers I and II; a high density in the dorso-lateral funiculus and in the reticular formation; a moderate density in layers III, IV and V; and a low density in layer VI. However, after intravenous or intrathecal administration of clonidine a decrease in fibers containing met-enkephalin was observed in layers I and II (high or moderate density), the dorso-lateral funiculus, and the reticular formation (moderate or low density), and in layers IV and V (low or very low density). In all cases, the decrease in the immunoreactivity was more marked when clonidine was administered intrathecally. Our results suggest that clonidine induces the release of met-enkephalin in the spinal cord. They further suggest that the opioid peptide released could be involved in the control of nociceptive transmission by inhibiting the release of neurotransmitters (e.g., substance P). In summary, our study shows that clonidine could be involved in antinociceptive mechanisms in the cat spinal cord. Histol. Histopathol. 13, 955-959 (1998)

 

Key words: Met-enkephalin, Clonidine, Spinal cord, Immunocytochemistry, Cat

DOI: 10.14670/HH-13.955