Hot-plate assay

The most commonly used analgesic tests utilize a chemical, thermal or mechanical nociceptive stimulus, for example, rodent paw pressure, tail flick or hot plate assays. 

SNX-111, when given alone, is active in the Chung model (spinal nerve ligation), tactile allodynia test (hindpaw UV burn) and paw pressure test. In the hot plate assay there is only a small but significant effect of about 20% increase in response latency (Table 4, Malmberg and Yaksh, 1994). 

Wesolowska A, Young S, Dukat M. MD-354 potentiates the antinociceptive effect of clonidine in the mouse tail-flick but not hot-plate assay. Eur J Pharmacol 2004 495 129-136. 

Langerman et al. (1995) evaluated the acute tolerance to continuous morphine infusion up to 8 h in the rat with various doses using the hot plate and the tail flick assay. Tolerance was observed with the hot plate assay but not with the tail flick assay suggesting tolerance development at a supraspinal site. 

Adult, male Sprague-Dawley rats were assessed for analgesic activity using the rat paw-hot plate assay. The latency hot plate paw withdrawal was measured by a Hot Plate Analgesia Meter. The temperature of the hot plate was set and calibrated at 52°C and the rats were removed from the heat stimulus by 36 seconds after placement. 

Mininmin effective dose (MED) in mouse hot-plate assay, i.p. (294, 342). 

Endorphin Analogs - D-Ala, N-MeMet -enkephallnamide ( ) has been found to be a potent parenteral analgesic.59 it was 238 times as potent as normor-phlne in the mouse vas deferens assay, and four times as potent as morphine in the mouse hot plate assay (jump response) after subcutaneous administration. It is claimed that has relatively little respiratory depressant properties or tendency to cause tolerance or physical dependence. A series of Met -enkephalin analogs extended at the amino terminus with amino acid residues corresponding to 6-LPH have been described. Using the guinea-pig ileum-myenteric plexus assay, potency was found to decrease dramatically on further extension of the g-LPH 60-65 sequence... 

Table 7. Activity in Mouse Hot Plate Assay (Minimum Effective Dose, pmol/kg) for Pyridyl Ether Compounds of General...

Clonidine also appears to have significant analgesic properties to which tolerance does not develop. Antinociceptive effects have been demonstrated in many of laboratory tests used to demonstrate analgesia. The effect is centrally mediated. For example, the hot plate assay that demonstrated analgetic properties for clonidine orally failed to do so for other imidazole a-mimetics such as oxymetazoline and tetrahydrazoline, which do not cross the BBB unless administered intracerebrally. 

Fig, 15. Analgesic potencies (ED5Q by hot plate assay, sc mg/kg, mice, morphine = 1.0)... 

B, Structure-Activity Studies - There is an Increasing tendency to use the newer tests (inflammed foot, writhing, bradykin) for evaluation of analgesic potency but, unless otherwise specified, potency estimates in the following discussion are based on the mouse hot plate assay. 

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