• Synapse · Jun 2015

    Recruitment of striatonigral disinhibitory and nigrotectal inhibitory GABAergic pathways during the organization of defensive behavior by mice in a dangerous environment with the venomous snake Bothrops alternatus (Reptilia, Viperidae).

    • Rafael Carvalho Almada and Norberto Cysne Coimbra.
    • Laboratory of Neuroanatomy and Neuropsychobiology, Department of Pharmacology, Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Ribeirão Preto, São Paulo, 14049-900, Brazil; Institute of Neuroscience and Behaviour (INeC), Monte Alegre, Ribeirão Preto, São Paulo, 14050-220, Brazil.
    • Synapse. 2015 Jun 1; 69 (6): 299-313.

    AbstractThe neuropsychopharmacological basis of fear- or panic-related behavior has been the focus of several studies. Some mesencephalic tectum (MT) structures, such as the superior colliculus (SC) and dorsal periaqueductal gray matter (dPAG), are considered to be responsible for the control of defensive responses evoked during threatening situations. Furthermore, the pars reticulata of the substantia nigra (SNpr) sends inputs to the SC that can work as a sensory channel to MT neurons fundamental for the elaboration of defensive responses. The purpose of the present study was to investigate the role of striato-nigral GABAergic inputs in the activity of nigro-tectal outputs during the elaboration of defensive behavior using a GABA(A) receptor selective blockade in the MT of mice confronted pre-treated with Bothrops alternatus. Mice with injections of physiological saline into the SNpr and treated with a GABA(A) receptor selective antagonist in the MT displayed an increase in panic-related behavior, expressed by an increase in the duration of freezing, frequency of nonoriented escape and frequency of total escape responses during the confrontation with the snake. However, intra-SNpr injections of cobalt chloride followed by MT injections of bicuculline caused a significant decrease in the duration of freezing and total escape responses. In addition, intra-SNpr injections of lidocaine followed by MT injections of bicuculline caused an increase in panic-related behavior. The results highlight the involvement of SNpr and MT structures in the organization of defensive behaviors and suggest an inhibitory control of striatonigral-nigrotectal pathways during the elaboration of fear- and panic-related behavior.© 2015 Wiley Periodicals, Inc.

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