Dopamine D1 and D2 receptor immunoreactivities in the arcuate-median eminence complex and their link to the tubero-infundibular dopamine neurons

  • W. Romero-Fernandez Karolinska Institutet, Sweden.
  • D.O. Borroto-Escuela Karolinska Institutet, Sweden.
  • V. Vargas-Barroso National Autonomous University of Mexico, Mexico.
  • M. Narváez University of Malaga, Spain.
  • M. Di Palma Carlo Bo University of Urbino, Italy.
  • L.F. Agnati Karolinska Institutet, Sweden.
  • J. Larriva Sahd National Autonomous University of Mexico, Mexico.
  • K. Fuxe | kjell.fuxe@ki.se Karolinska Institutet, Sweden.

Abstract

Dopamine D1 and D2 receptor immunohistochemistry and Golgi techniques were used to study the structure of the adult rat arcuate-median eminence complex, and determine the distribution of the dopamine D1 and D2 receptor immunoreactivities therein, particularly in relation to the tubero-infundibular dopamine neurons. Punctate dopamine D1 and D2 receptor immunoreactivities, likely located on nerve terminals, were enriched in the lateral palisade zone built up of nerve terminals, while the densities were low to modest in the medial palisade zone. A codistribution of dopamine D1 receptor or dopamine D2 receptor immunoreactive puncta with tyrosine hydroxylase immunoreactive nerve terminals was demonstrated in the external layer. Dopamine D1 receptor but not dopamine D2 receptor immnunoreactivites nerve cell bodies were found in the ventromedial part of the arcuate nucleus and in the lateral part of the internal layer of the median eminence forming a continuous cell mass presumably representing neuropeptide Y immunoreactive nerve cell bodies. The major arcuate dopamine/ tyrosine hydroxylase nerve cell group was found in the dorsomedial part. A large number of tyrosine hydroxylase immunoreactive nerve cell bodies in this region demonstrated punctate dopamine D1 receptor immunoreactivity but only a few presented dopamine D2 receptor immunoreactivity which were mainly found in a substantial number of tyrosine hydroxylase cell bodies of the ventral periventricular hypothalamic nucleus, also belonging to the tubero-infundibular dopamine neurons. Structural evidence for projections of the arcuate nerve cells into the median eminence was also obtained. Distal axons formed horizontal axons in the internal layer issuing a variable number of collaterals classified into single or multiple strands located in the external layer increasing our understanding of the dopamine nerve terminal networks in this region.  Dopamine D1 and D2 receptors may therefore directly and differentially modulate the activity and /or Dopamine synthesis of substantial numbers of tubero-infundibular dopamine neurons at the somatic and terminal level. The immunohistochemical work also gives support to the view that dopamine D1 receptors and/or dopamine D2 receptors in the lateral palisade zone by mediating dopamine volume transmission may contribute to the inhibition of luteinizing hormone releasing hormone release from nerve terminals in this region.

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Author Biographies

W. Romero-Fernandez, Karolinska Institutet

Department of Neuroscience

D.O. Borroto-Escuela, Karolinska Institutet
Department of Neuroscience
V. Vargas-Barroso, National Autonomous University of Mexico

Institute of Neurobiology

M. Narváez, University of Malaga

Andalusia Tech

M. Di Palma, Carlo Bo University of Urbino

Department of Earth, Life and Environmental Sciences, Section of Physiology

L.F. Agnati, Karolinska Institutet

Department of Neuroscience

J. Larriva Sahd, National Autonomous University of Mexico

bInstituto de Neurobiología

K. Fuxe, Karolinska Institutet

Department of Neuroscience

Published
2014-07-18
Section
Original Papers
Supporting Agencies
Swedish Research Council, Swedish Royal Academy of Sciences, Karolinska Institutets Forskningsstiftelser
Keywords:
Dopamine D1 and D2 receptors, tubero-infundibular dopamine neurons, dopamine receptor colocalization, arcuate-median eminence complex, volume transmission, luteinizing hormone, releasing hormone.
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How to Cite
Romero-Fernandez, W., Borroto-Escuela, D., Vargas-Barroso, V., Narváez, M., Di Palma, M., Agnati, L., Larriva Sahd, J., & Fuxe, K. (2014). Dopamine D1 and D2 receptor immunoreactivities in the arcuate-median eminence complex and their link to the tubero-infundibular dopamine neurons. European Journal of Histochemistry, 58(3). https://doi.org/10.4081/ejh.2014.2400