Stm200

This was a within-subjects 2-d experiment separated by ∼24 h. Conditioned stimuli were pictures of animals, tools, and food on a white background obtained from the website www.lifeonwhite.com or publicly available sources on the internet. The US was a 6 msec electrical shock delivered to the right wrist from the BIOPAC (Goleta, CA) STM200 and calibrated before the session to a level deemed “highly annoying but not painful.” Trial order was pseudorandomized such that no more than three pictures of the same category appeared in a row. The task was presented using E-Prime 2.0 and consisted of a trial-unique category conditioning design, meaning that each trial was a different basic-level exemplar with a unique name. For example, there were no two different pictures of a monkey. Pictures of common phobic stimuli (e.g., spiders, snakes, weapons) or highly appealing food images were not used in the CS set. CSs were on the screen for 6 sec, followed by a 6–8 sec waiting period with a fixation cross on a white background. On each trial, subjects rated expectancy for the shock using a two-alternative forced choice rating scale. Subjects were not instructed about the CS–US contingencies, but were told that if they paid attention then they might learn an association between the pictures and the shock.

ERG was performed 7 days after treatment. The rats were first adapted by keeping them for 30 minutes in the dark. Subsequently, the animals were anesthetized and corneal silver electrode was placed on the cornea, the reference needle electrode (#EL452, Biopac System, Goleta, CA, USA) was placed subcutaneously in the region of the skull and ground needle electrode (#EL450, Biopac System) was placed subcutaneously at the base of the tail (Shabelnikova et al., 2016). A stroboscope TSD122B with a flash of white light connected to the stimulator (#STM200, Biopac System) was placed in front of the animal. Evoked biopotentials were amplified using ERS100C Evoked Response Amplifier (#ERS100C, Biopac System). An MP150 data acquisition and analysis system (#MP150, Biopac Systems) was used to represent them graphically. Each rat was subjected to only a single stimulation of 0.5 seconds to obtain the ERG recording. Changes in the amplitudes of the a- and b-waves of ERG were used to assess the functional state of the retina after pre-treatment with MgAT and NMDA exposure. The readings from each group of eight animals were included into the protocol and used to calculate the mean.