ON and OFF components of the receptive fields have different latencies to diffuse flashes of light in the superior colliculus of golden hamsters

Shock sensitization and fear potentiation of auditory startle response in hamsters

It is well known that an auditory startle response can be modulated by several processes. In the present study shock sensitization and fear potentiation were examined in 17 hamsters to assess whether response enhancement is similar for another rodent. Immediately after presentation of electrical foot shocks, the auditory startle response increased significantly. This response was also enhanced after fear conditioning in the Experimental group using a light as a conditioned stimulus (CS) and the foot shock as the unconditioned stimulus (US). The auditory startle response remained unchanged in the Control group after nonpaired presentation of CS and US. Significant correlation between enhancement of the auditory startle response in sensitization and fear conditioning was found for the Experimental group. Shock sensitivity and effect of fear on modulation of the auditory startle response in hamsters are similar to those of other rodents. Further, neural mechanisms underlying enhancement of the auditory startle response seem not to be responsible for the deficit of prepulse inhibition in hamsters.

Light-dark discrimination after sciatic nerve transplantation to the sectioned optic nerve in adult hamsters

In adult golden hamsters (Mesocricetus auratus), the optic nerve was bilaterally sectioned with one side grafted with the sciatic nerve to make a bridge to the ipsilateral superior colliculus. Shuttle-box avoidance was tested using light as the conditioned stimulus. Three of the five transplanted animals revealed statistically significant increase in percentages of avoidance. A significant increase in the avoidance scores was also observed in 15 normal hamsters, but none of 13 blind hamsters showed such an increase. Intertrial responses, which represent spontaneous responses, did not show significant changes. We conclude that some of the transplanted animals can discriminate between light and dark, probably through their restored visual pathway.

Comparative investigation of retinal responses to brief light stimuli: 2-amino-4-phosphonobutyrate studies--I. Frog retina, Rana ridibunda

1. Electroretinogram (ERG) and responses of single ganglion cells to 75 microseconds light flashes, applied at two different backgrounds, were studied. Additionally, a stimulation with long-lasting stimuli (ordinarily 5 sec ON-, 5 sec OFF-) was used. Both white and coloured light stimuli were presented. 2. 150 microM 2-amino-4-phosphonobutyrate (APB) was used to separate OFF- from ON- channels. 3. Before APB application, one or two components in the impulse activity in response to a flash were observed, depending on the type of ganglion cell (ON-, OFF- or ON-OFF). the latency of the first component was 60 msec and the latency of the second one was from 160 to 430 msec on average, at different background conditions. APB abolished the first component and enhanced the second one. 4. By means of APB, two components were shown to exist in the main positive wave of the flash ERG. APB abolished the first component and did not influence or enhance the second one. 5. The data obtained show that both ON- and OFF- channels take part in the generation of the frog retinal responses to brief stimuli.

Comparative investigation of retinal responses to brief light stimuli: 2-amino-4-phosphonobutyrate studies--II. Turtle retina (Emys orbicularis)

1. Electroretinogram (ERG) and responses of single ganglion cells to 75 microseconds light flashes, presented on two different backgrounds, were studied. Additionally, stimulation with long lasting stimuli (ordinarily 5 sec ON-, 15 sec OFF-) was used. 2. 2-amino-4-phosphonobutyrate (APB) at a concentration of 450 microM on average was used to separate OFF- from ON- channels. It is known, that in other species APB selectively blocks the activity of ON- channel only. 3. The existence of APB- sensitive membrane receptors was demonstrated in the turtle retina. As in other species, APB abolished the ERG b-wave and enhanced the d-wave, when long lasting stimulation was used. 4. By means of APB, two components were shown to exist in the ERG positive wave in response to a flash. APB abolished the first component and did not influence or enhanced the second one. 5. By means of APB, one or two components in the impulse activity in response to flash were demonstrated, depending on the type of ganglion cell (ON-, OFF- or ON-OFF). The latency of the first component was 70 msec and the latency of the second one 210 msec on average. APB abolished the first component, and enhanced the second one. 6. The data obtained show that both ON- and OFF- channels take part in the generation of the turtle retinal responses to brief stimuli. 7. Based on the results obtained, some peculiarities of the network organization of the ganglion cells' receptive fields are discussed.