Responses of nociceptive VPL neurons to intracardiac injection of bradykinin in the cat.

Responses of nucleus ventralis posterolateralis (VPL) neurons to intracardiac injection of bradykinin (2 micrograms/kg) were examined in urethane-chloralose anesthetized cats. A total of 39 VPL neurons were subjected to the study. Nociceptive specific (NS) and wide dynamic range (WDR) neurons receiving both cutaneous nociceptive and cardiac sympathetic afferent inputs regularly exhibited an increased discharge in response to intracardiac bradykinin. NS and WDR neurons unresponsive to cardiac sympathetic afferents and low threshold mechanoreceptive (LTM) neurons did not respond to intracardiac bradykinin. Both NS and WDR neurons responsive to intracardiac bradykinin were located in the shell region of the caudal VPL. These cutaneous nociceptive neurons may be involved in transmitting cardiac nociceptive information to the cerebral cortex in the cat.