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Direct and indirect nigrofugal projections to the nucleus reticularis pontis caudalis mediate in the motor execution of the acoustic startle reflex.
- Source :
-
Brain structure & function [Brain Struct Funct] 2018 Jul; Vol. 223 (6), pp. 2733-2751. Date of Electronic Publication: 2018 Mar 24. - Publication Year :
- 2018
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Abstract
- The acoustic startle reflex (ASR) is a short and intense defensive reaction in response to a loud and unexpected acoustic stimulus. In the rat, a primary startle pathway encompasses three serially connected central structures: the cochlear root neurons, the giant neurons of the nucleus reticularis pontis caudalis (PnC), and the spinal motoneurons. As a sensorimotor interface, the PnC has a central role in the ASR circuitry, especially the integration of different sensory stimuli and brain states into initiation of motor responses. Since the basal ganglia circuits control movement and action selection, we hypothesize that their output via the substantia nigra (SN) may interplay with the ASR primary circuit by providing inputs to PnC. Moreover, the pedunculopontine tegmental nucleus (PPTg) has been proposed as a functional and neural extension of the SN, so it is another goal of this study to describe possible anatomical connections from the PPTg to PnC. Here, we made 6-OHDA neurotoxic lesions of the SN pars compacta (SNc) and submitted the rats to a custom-built ASR measurement session to assess amplitude and latency of motor responses. We found that following lesion of the SNc, ASR amplitude decreased and latency increased compared to those values from the sham-surgery and control groups. The number of dopamine neurons remaining in the SNc after lesion was also estimated using a stereological approach, and it correlated with our behavioral results. Moreover, we employed neural tract-tracing techniques to highlight direct projections from the SN to PnC, and indirect projections through the PPTg. Finally, we also measured levels of excitatory amino acid neurotransmitters in the PnC following lesion of the SN, and found that they change following an ipsi/contralateral pattern. Taken together, our results identify nigrofugal efferents onto the primary ASR circuit that may modulate motor responses.
- Subjects :
- Acoustic Stimulation
Animals
Auditory Pathways drug effects
Biotin analogs & derivatives
Biotin metabolism
Connectome
Dextrans metabolism
Functional Laterality drug effects
Male
NADPH Dehydrogenase metabolism
Neurotoxins toxicity
Neurotransmitter Agents metabolism
Oxidopamine toxicity
Rats
Rats, Wistar
Reaction Time drug effects
Reaction Time physiology
Reflex, Startle drug effects
Reticular Formation drug effects
Spinal Cord cytology
Spinal Cord drug effects
Stilbamidines metabolism
Substantia Nigra injuries
Tyrosine 3-Monooxygenase metabolism
Auditory Pathways physiology
Movement physiology
Reflex, Startle physiology
Reticular Formation physiology
Substantia Nigra physiology
Subjects
Details
- Language :
- English
- ISSN :
- 1863-2661
- Volume :
- 223
- Issue :
- 6
- Database :
- MEDLINE
- Journal :
- Brain structure & function
- Publication Type :
- Academic Journal
- Accession number :
- 29574585
- Full Text :
- https://doi.org/10.1007/s00429-018-1654-9