Hot Plate Technique Research Articles

Effect of rifampicin on development of tolerance to analgesic actions of morphine

Two series of experiments were performed. In the first series the reaction times of mice were determined using the hotplate technique. In the second series of experiments the reactions of rats were determined using the electric footshock technique. In both series of experiments morphine was observed to alter the responses, and chronic morphine administration resulted in tolerance to these actions of morphine. In both series of experiments, tolerance, defined by these same criteria, was inhibited by the concurrent administration of rifampicin.

Morphine analgesia, two-way avoidance, and consummatory behavior following lesions in the midbrain raphe nuclei of the rat

Rats with lesions in the median raphe nucleus (MR group) or in both the dorsal and median raphe nuclei (R group) were compared with operated control animals on the following measures: telencephalic serotonin (5-HT) concentration; daily water consumption; acquisition of a two-way conditioned avoidance response; and morphine analgesia. Both lesions produced significant reductions in telencephalic 5-HT, reaching 33% in the MR group and 57% in the R group. Transient increases in water intake were observed in both groups, being more prolonged and of greater magnitude in the R group. On the other hand, facilitated shuttlebox avoidance learning was observed only in the R group. Neither lesion affected pain sensitivity or morphine (3–9 mg/kg) analgesia as measured by the hot-plate technique. Therefore, while the midbrain raphe appears to be involved in the regulation of water intake and some behavioral responses to painful stimuli, lesions in these nuclei and reduction of telencephalic 5-HT are not sufficient to block morphine analgesia.

Imidazole, calcium and analgesia

In this paper the results obtained with some narcotic analgesic and analgesic-antipyretic drugs are presented. The technique of Reinhard and Beer and the Hot Plate technique have been used for narcotic analgesics and the writhing test for analgesic-antipyretics. Imidazole increases the general analgesic effects and calcium ions antagonize these effects. Imidazole itself exerts a definite analgesic action.

Activity of major analgesics on motor nociceptive responses in decerebrate mice.

Three major analgesics (morphine, pentazocine, methotrimeprazine) were tested on intact and decerebrate mice for their ability to prolong the reaction time of motor nociceptive responses in two established analgesimetric tests: the thermal receptacle and the hot-plate method. In intact mice only morphine showed a marked dose-dependent anti-nociceptive activity by both methods. Methotrimeprazine ranked higher than morphine, as measured by its ED50, in the hot-plate method, but it showed an early ceiling effect in the thermal receptacle technique. Pentazocine showed a very early ceiling effect in both tests. Transections tangent to the superior colliculi did not significantly modify the mean reaction times recorded in either of the two methods, though they caused a significant change in the pattern of response of mice tested by the hot-plate technique. Drug parameters, as ED50's and slope functions, remained unchanged following decerebration, except for a significant drop in the potency of morphine as determined by the thermal receptacle method. The relevance of these findings to mechanisms of analgesic action and the reliability of analgesic screening are discussed.

Pharmacological properties related to the mechanism of action of potent analgesic drugs.

Abstract