Most of the studies described in this monograph were carried out in the
Department of Anatomy, Histology and Embryology at Thracian University
in Stara Zagora, Bulgaria. Some of the in situ hybridization experiments
were performed at the Department of Anatomy and Cell Biology, University
ofUlm, Germany and the tracer experiments were conducted at the
Department ofPhysi- ology, Leiden University, The Netherlands. In 1992,
we started elucidating the ultrastructural organization and synaptic
connections of the mesencephalic trigeminal nu- of its neuronal po-
cleus as well as the related chemical coding 1ation, the putative
neurotransmitters utilized by MTN neurons and their possible sources. In
the years to come, painstaking research was focused on this subject and
we were able to identify certain neuroactive substances in this unique
nucleus, including classical and peptide transmitters. I spent the
period of 1995-1997 in Germany as a fellow of the Alexander von Humboldt
Foundation, at the department headed by Prof. Dr. Christof Pilgrim.
During this stretch of time, I ac- quired the in situ hybridization
technique. It allowed me to expand my investigations and detect the
expression of dopamine receptors and newly synthesized neuropeptides in
MTN neurons after peripheral injury of their axons, not only at protein
but also at mRNA levels.