|Budget Amount *help
¥2,800,000 (Direct Cost : ¥2,800,000)
Fiscal Year 1999 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1998 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Conditioned fear stimuli inhibit secretion of vasopressin, facilitate secretion of oxytocin or prolactin by the pituitary and suppress motor activity. To identify the locations of the NMDA receptors in the brain that are activated during recall process of emotional memory, we examined in male rats whether an NMDA receptor antagonist, MK-801 infused in the localised areas of the brain 30 mm before conditioned fear stimuli blocks expression of conditioned fear responses. Physiological saline was infused in the control groups.
1. Destruction of the amygdala: Rats were trained with electric foot shocks. On the next day, a neurotoxin, NMDA was infused in to the amygdala bilaterally under anaesthesia. One week after the surgery, rats were tested with conditioned fear stimuli. Neuroendocrine and behavioural fear responses were impaired in the NMDA groups.
2. MK-801 in the amygdala: The neuroendocrine and behavioural responses to conditioned fear stimuli were not blocked in the NMDA- or Saline infused rats.
3. MK-801 in the nucleus of tractus solitarius (NTS): In the rats infused with MK-801 30 min before conditioned fear stimuli, VP but not OT, PRL or motor activity response was impaired. Thus the NMDA receptor in the NTS could not be essential for the recall process or emotional memory.
4. MK-801 in the bed nucleus of the stria terminalis (BNST): In the antagonist- but not saline-injected rats, VP and PRL responses were impaired and motor inhibition was reduced after fear stimuli, significantly. The results suggest that NMDA receptors in the BNST play a significant role in recall of emotional memory.