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Distribution and origin of the catecholaminergic innervation in the amphibian mesencephalic tectum

Published online by Cambridge University Press:  05 September 2002

CRISTINA SÁNCHEZ-CAMACHO
Affiliation:
Departamento de Biología Celular, Facultad de Biología, Universidad Complutense of Madrid, Spain
OSCAR MARÍN
Affiliation:
Department of Psychiatry and Langley Porter Psychiatric Institute, Nina Ireland Laboratory of Developmental Neurobiology, University of California at San Francisco
AGUSTÍN GONZÁLEZ
Affiliation:
Departamento de Biología Celular, Facultad de Biología, Universidad Complutense of Madrid, Spain

Abstract

The mesencephalic tectum plays a prominent role in integrating both visual and multimodal sensory information essential for normal behavior in amphibians. Activity in the mesencephalic tectum is thought to be modulated by the influence of distinct neurochemical inputs, including the catecholaminergic and the cholinergic systems. In the present study, we have investigated the distribution and the origin of the catecholaminergic innervation of the mesencephalic tectum in two amphibian species, the anuran Rana perezi and the urodele Pleurodeles waltl. Immunohistochemistry for dopamine and two enzymes required for the synthesis of catecholamines, tyrosine hydroxylase (TH) and dopamine β-hydroxylase (DBH), revealed a complex pattern of catecholaminergic (CA) innervation in the anuran and urodele mesencephalic tectum. Dopaminergic fibers were primarily present in deep tectal layers, whereas noradrenergic (DBH immunoreactive) fibers predominated in superficial layers. Catecholaminergic cell bodies were never observed within the tectum. To determine the origin of this innervation, applications of retrograde tracers into the optic tectum were combined with immunohistochemistry for TH. Results from these experiments demonstrate that dopaminergic neurons in the suprachiasmatic and juxtacommissural nuclei (in Rana) or in the nucleus pretectalis (in Pleurodeles), together with noradrenergic cells of the locus coeruleus, are the sources of CA input to the amphibian mesencephalic tectum. The present results suggest that similar CA modulatory inputs are present in the mesecencephalic tectum of both anurans and urodeles.

Type
Research Article
Copyright
2002 Cambridge University Press

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