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Antagonism to the effect of morphine on electric discharges of pain-related neurons in nucleus parafascicularis of thalamus by cholecystokinin octapeptide

Xu Manying, Sun Mingzhi, Zhang Limin, Wang Binming, Han Jisheng

Department of Physiology, Harbin Medical University；Department of Physiology, Beijing Medical University. Beijing, China

Abstract

It was reported that the antinociceptive effect of morphine as determined by
the latency of the radiant heat induced tail flick response was antagonized by cholecystokinin octapeptide (CCK-8) administered intracerebroventricularly (ICV). In the present study the effect of morphine on the electric activities of simultaneously recorded pain-related neurons of nucleus parafascicularis in both sides of the rat brain were studied after ICV injection of CCK-8. The results were as follows: (1) Intraperitoneal injection of morphine (10mg/kg) resulted in an inhibition of the evoked response of the pain-excitation neurons (PEN) as well as an excitation of the evoked response of the pain-inhibition neurons (PIN).(2) Both the inhibitory effect of morphine on the electric discharges of PEN and the excitatory effect of morphine on the electric activities of PIN were almost eliminated by the ICV administration of CCK-8 at a dose of 15 ng. No significant effect was observed when unsulfated CCK-8 was used instead of CCK-8.(3) In some of the animals, recordings were made frorn a PEN and a PIN simultaneously in each side of the nucleus parafascicularis. It was clearly shown that administration of CCK-8 resulted in a reversal of the effect of morphine, irrespective of the recorded neuron being PEN or PIN. The results are consistent with the conclusion obtained in the previous study using tail flick latency as the endpoint of nociception, i. e., CCK-8 is antagonistic
to the antinociceptive effect of morphine.

Key words: Cholecystokinin;Morphine;Nucleus parafascicularis;Intracerebroventricular injection;Pain-related neurons

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Citing This Article：

Xu Manying, Sun Mingzhi, Zhang Limin, Wang Binming, Han Jisheng. Antagonism to the effect of morphine on electric discharges of pain-related neurons in nucleus parafascicularis of thalamus by cholecystokinin octapeptide. Acta Physiol Sin 1987; 39 (4): (in Chinese with English abstract).