Relationship between Behavioral Recovery from Unilateral 6-OHDA
Lesion of the Substania Nigra and Changes in the Tuberomammillary-Striatal
Projection as Measured by HRP-Labelling
Affiliations: Bilaney Consultants GmbH, Düsseldorf, Germany | Institute of Physiological Psychology I and
Biologisch-Medizisches Forschungszentrum, University of Düsseldorf,
Germany
Note: [] Corresponding author: J.P. Huston, Institute of Physiological Phychology I and
Biologisch-Medizinisches Forschungszentrum, University of Düsseldorf,
Universitätstr. 1, 40225 Düsseldorf, Germany
Abstract: The tuberomammillary nucleus (TM) is the only known neuronal cell
group in the brain which contains histamine. There is evidence for a reciprocal
relationship between the effects of histamine and dopamine on behavior. A
unilateral lesion of dopamine cells in the Substantia Nigra (SN) results in
asymmetrical behavior, and recovery from this asymmetry was previously found to
be associated with asymmetrical changes in the nigro-striatal projection as
determined by anatomical tracing technique. In view of the apparent opposing
interaction between the TM and the SN, we examined whether the
tuberomammillary-striatal projection also shows changes after a unilateral
lesion of the SN. Rats had 6-OHDA injected into one substantia nigra and were
tested for behavioral asymmetry over a 15 day period. Horseradish peroxidase
(HRP) was then deposited in the caudate-putamen (CPU) ipsilateral to the
lesion. Controls devoid of a lesion had the tracer deposited in either the
right of left CPU. More HRP-labeled cells were found in the anterior part of TM
ipsilateral to the lesion in the animals which failed to recover from
lesion-induced asymmetry in turning behavior, as compared to normal controls or
animals which showed behavioral recovery. The labeled cells in the anterior
part of the ipsilateral TM were smaller in animals examined 15 days after the
lesions than in the control animals. The results indicate an increase in HRP
uptake or transport in the anterior part of the tuberomammillary-striatal
projection predominantly ipsilateral to the lesion in animals which failed to
recover from lesion induced asymmetry. Previously, we had found an opposite
effect in the nigro-striatal projection, namely an increase in HRP uptake or
transport only in animals which recovered from their lesion induced asymmetry.
The results are discussed in terms of the evidence for a reciprocal
relationship between the TM- and SN-striatal systems.
