1998 年 10 巻 2 号 p. 73-79
The aim of this study was to elucidate whether an intracerebroventricular (icv) administration of oxytocin would affect the somatosensory system in anesthetized rats or not. The effect was evaluated by recording cortical somatosensory evoked potentials (SEPs) in pentobarbital-anesthetized rats. The effect was also compared with that of morphine. The SEPs were recorded from the primary sensory cortex with skull screw electrodes. The electrical stimulation of the forelimb elicited four components, a primary positive wave (P1), a primary negative wave (N1), a secondary positive wave (P2) and a secondary negative wave (N2) in the contralateral sensory cortex. The icv administration of oxytocin (0.05-5 μg) had no effect on the peak latency of the P1, N1, P2 or N2 wave, or on the peak-to-peak amplitudes of P1N1 and P2N2. In contrast, the icv administration of morphine (5 μg) prolonged the peak latencies of all four components and reduced the amplitudes of both P1N1 and P2N2. These actions of morphine were antagonized by a subsequent icv administration of naloxone (5 μg). The present results suggest that oxytocin does not influence the somatosensory system in anesthetized rats, while morphine inhibits the system via opioid receptors.
