The modulation of striatonigral and nigrotectal pathways by CB1 signalling in the substantia nigra pars reticulata regulates panic elicited in mice by urutu-cruzeiro lancehead pit vipers.

The modulation of striatonigral and nigrotectal pathways by CB1 signalling in the substantia nigra pars reticulata regulates panic elicited in mice by urutu-cruzeiro lancehead pit vipers.
Behav Brain Res. 2020 Nov 07;:112996
Authors: Almada RC, Anjos-Garcia TD, da Silva JA, Pigatto GR, Wotjak CT, Coimbra NC
Abstract
Cannabinoid receptor type 1 (CB1R) is widely distributed in the substantia nigra pars reticulata (SNpr). However, the role of CB1R at the SNpr level in threatening situations is poorly understood. We investigated the role of CB1R in the SNpr on the expression of fear responses in mice confronted with urutu-cruzeiro pit vipers. First, a bidirectional neurotracer was injected into the SNpr; then, immunostaining of the vesicular GABA transporter was conducted at the levels of the striatum (CPu) and deep layers of the superior colliculus (dlSC). In addition, CB1R immunostaining and GABA labelling were performed in the SNpr. Using a prey-versus-snake paradigm, mice were pretreated with the CB1R antagonist AM251 (100 pmol) and treated with the endocannabinoid anandamide (AEA, 5 pmol) in the SNpr, followed by bicuculline (40 ng) in the dlSC, and were then confronted with a snake. Bidirectional neurotracers associated with immunofluorescence showed the GABAergic striatonigral and nigrotectal pathways. Furthermore, we showed that CB1R labelling was restricted to axonal fibres surrounding SNpr GABAergic cells. We also demonst...

Source: Behavioural Brain Research - November 7, 2020 Category: Neurology Authors: Almada RC, Anjos-Garcia TD, da Silva JA, Pigatto GR, Wotjak CT, Coimbra NC Tags: Behav Brain Res Source Type: research