Abstract
The amplitude of the startle reflex is elevated when elicited in the presence of a cue previously paired with footshock, fear potentiated startle. This suggests a possibility of evaluation of the other emotion such as pleasure and aversive. Our objective is to study a modulation effect in rat startle response by reward-related and aversive-related conditioned stimuli (CS). Male albino Wistar rats, weighing 300-350g, were used. Oral cannuellae was implanted in each animal oral, and the other terminal of the tube was fixed on the head. Startle stimulus was a 40 msec burst of white noise. The CS of 3.2 sec duration was produced by 3 LED (420 Lux). The unconditioned stimulus was a shock generated by scramble shocker (0.2, 0.4, 0.6 mA in strength and 0.2 sec duration), 10% glucose solution or 5% saline solution. The startle response was increased by conditioning of aversive stimuli. The startle amplitude was 518±593 (relative units, n=3) in aversive CS, compared with 348±345 of tone alone. However, the response was not changed by reward conditioning. The startle amplitude was 106±136 (relative units, n=8) in aversive CS, compared with 120±139 of tone alone. The startle amplitude was enhanced proportionally by CS corresponded to electrical current intensity in fear conditioning. However, the startle amplitude showed an inverse U-shaped responses in discrimination learning of CS associated with different UCS intensity. These suggest that startle response might depend on quantity and quality of emotion. [Jpn J Physiol 54 Suppl:S204 (2004)]
