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GABAergic nigro-collicular pathways modulate the defensive behaviour elicited by midbrain tectum stimulation
1Departamento de Morfologia, FMRP, Universidade de São Paulo, Brasil.
Behavioural Brain Research
|December 31, 1993
Summary
GABAergic fibers from the substantia nigra, pars reticulata (SNpr) inhibit defensive behaviors. Lesioning the SNpr decreased aversion thresholds, while enhancing GABAergic transmission in the SNpr mimicked these effects.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
Background:
- Midbrain tectum (MT) structures, including the periaqueductal gray and superior colliculus, are crucial for defensive behaviors.
- Electrical stimulation or GABA antagonist microinjections into the MT elicit aversive behaviors.
Purpose of the Study:
- To investigate the role of nigrocollicular GABAergic fibers in modulating defensive behaviors.
- To determine if the substantia nigra, pars reticulata (SNpr) influences aversive responses originating from the MT.
Main Methods:
- Rats underwent neurochemical lesions of the substantia nigra (pars reticulata and compacta) using kainic acid.
- Microinjections of bicuculline (GABA antagonist) or electrical stimulation were applied to the MT.
- GABAergic transmission in the SNpr was manipulated using muscimol (enhancement) or bicuculline (inhibition).
Main Results:
- SNpr lesions significantly decreased aversive thresholds and increased responsiveness to MT bicuculline microinjections.
- Microinjections of bicuculline into the SNpr produced opposite effects to SNpr lesions.
- Enhancing GABAergic transmission in the SNpr with muscimol mimicked the effects of SNpr lesions.
Conclusions:
- GABAergic fibers originating from the substantia nigra, pars reticulata, exert inhibitory control over aversive behaviors.
- These findings highlight a critical role for the nigrocollicular pathway in regulating defensive responses mediated by the midbrain tectum.