• DOI:10.1111/j.2042-7158.1969.tb08312.x
• Corpus ID: 33578310

The effect of narcotics and narcotic antagonists on the tail‐flick response in spinal mice

@article{Dewey1969TheEO,
  title={The effect of narcotics and narcotic antagonists on the tail‐flick response in spinal mice},
  author={William L. Dewey and James W. Synder and Louis S. Harris and John F. Howes},
  journal={Journal of Pharmacy and Pharmacology},
  year={1969},
  volume={21}
}

• W. Dewey, J. Synder, +1 author J. Howes
• Published 1 August 1969
• Biology
• Journal of Pharmacy and Pharmacology

Irwin, Houde & others (1951) reported that the tail-flick response of rats to radiant heat has the characters of a simple reflex. The ability of spinal rats to respond to this stimulus has been confirmed and extended (Winter & Flataker, 1951 ; Bonnycastle, Cook & Ipsen, 1953). Morphine inhibited the reflex in spinal rats but a quantitative difference observed between its effect in spinal rats and intact animals indicated that a second action might exist in its capacity to increase supraspinal inhibitory mechanisms. We have used the tail-flick test in mice to elucidate the mechanism of action of morphine and the narcotic-antagonist analgesics (Harris & Pierson, 1964 ; Dewey, Harris & others, 1969 ; Harris, Dewey & others, 1969) and have found a high correlation of activity with a number of narcotic analgesics to exist between species. We have confirmed and extended the observation that cholinergic agents such as oxotremorine and physostigmine also reduced this response (Harris & others, 1969; Howes, Harris & others, 1969). In addition, we have shown that an increase in central adrenergic or 5-hydroxytryptamine tone will increase the activity of morphine in intact mice in the tail-flick test (Dewey, Harris & others, 1968). We have now attempted to increase our knowledge about this testing procedure by studying the narcotics, the narcotic antagonists, and some of the neurochemicals discussed above in spinal mice. Male albino mice of the Swiss-Webster strain (18-25 g) had transections made under ether anaesthesia. A dorsal midline incision was made and the spinal cord was exposed between the fifth and sixth thoracic vertebrae. The cord was cauterized and the wound was closed with silk sutures. Attempts to transect the cord at a higher level resulted in death from respiratory paralysis or uncontrolled bleeding. There were few deaths from the surgical procedure. Water and food were presented ad libitum. Within 3 to 4 h all mice were quite active. Simple physiological stimuli showed that the cord section was positive. Most of the mice responded to the radiant stimulus of the tail-flick apparatus within 4 s, the variability among the reaction times being less than is usually observed in normal mice. Animals not responding within 4 s were not used. The results obtained were averaged with a second reading taken 30 min later, after which the drug was given subcutaneously in the flank; readings were made 20 min later. Mice not responding within 10 s were removed from the apparatus and considered to be 100% affected. The % maximal possible inhibition was calculated using the following formula :