Abstract
An initial systemic injection of morphine produces a fall in core temperature in the rat and this effect can be reproduced by intracerebral injection of the drug into the region of the anterior hypothalamic nuclei. The hypothermic response to either systemic or central injection can be arrested by intravenous administration of nalorphine. When intravenous nalorphine antagonizes intracerebral morphine a marked hyperthermia occurs. This hyperthermia appears to be an action of morphine which nalorphine does not antagonize. Injection of nalorphine into the anterior hypothalamic mus also reverses the fall in temperature following administration of morphine either systemically or centrally. Injection of nalorphine into other regions of the hypothalamus does not reverse the hypothermic response to morphine. It is concluded that the site of action of morphine in producing a fall in core temperature in rats is on the thermoregulatory centers in the anterior hypothalamus.
Footnotes
- Accepted June 30, 1965.
- The Williams & Wilkins Comapny
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