Table 1.
Rat strain differences of relevance to pain
| Trait | Parameters | Administration | Stimulus | Strain Difference* | Ref. |
|---|---|---|---|---|---|
| Nociceptive sensitivity | |||||
| Thermal | TW | WAG > F344 | 117 | ||
| TF | LE = LEW = WIS > F344 = SD | 118 | |||
| HP | LEW > F344 | 119 | |||
| Electrical | FJ | F344 > SD | 120 | ||
| Mechanical | CD | LEW > F344 | 121 | ||
| VF | F344 = LEW = WIS > SD | 42 | |||
| Chemical | CFA | LEW > SD | 122 | ||
| CFA | LEW > AVN | 123 | |||
| Neuropathic | NT | SD > WKY | 124 | ||
| NT | LE = SAB = SD = WKY > LEW | 125 | |||
| NT | BUF = SD > BN > WIS > LEW | 126 | |||
| Analgesia | |||||
| Morphine | 0–15 mg/kg | i.p. | FJ | SD > F344† | 120 |
| 0–10 mg/kg | i.p. | TF | SD > WIS | 127 | |
| 0–10 mg/kg | i.p. | TW | F344 > WAG | 117 | |
| 0–20 mg/kg | i.p. | FT | F344 > LEW | 41 | |
| 0–10 mg/kg | i.p. | TF | LE = SD ≥ LEW = WIS ≥ F344 | 118 | |
| 0–10 mg/kg | s.c. | HP | SD > WKY | 128 | |
| Codeine | 50–400 μmol/kg | s.c. | TF | SD > DA | 116 |
| Clonidine | 0–60 μg/kg | i.p. | FT | SD > WKY‡ | 129 |
| 10 μg | i.c.v. | TW | WAG > F344 | 130 | |
| TRH | 1 mg/kg | i.p. | TW | WAG > F344 | 131 |
| Serotonin | 0–300 μg/kg | i.v. | TF | SD > WKY | 132 |
| 0.5 μg | i.c.v. | TW | F344 > WAG | 130 | |
| Footshock | 1.5 mA | TW | F344 > SD§ | 133 | |
| Restraint | 30 min in tubes | TF | LE = SD > F344 = LEW = WIS | 118 | |
| Acupuncture | 100 Hz, 1–3 mA | TF | P77PMC > WIS | 134 | |
| Analgesic tolerance | |||||
| Morphine | 14 × 5–10 mg/kg | i.p. | TF | SD > WIS | 127 |
| 8 × 10 mg/kg | s.c. | HP | WKY > SD | 128 |
Strain Abbreviations: BN, Brown Norway; BUF, Buffalo; DA, Dark Agouti; F344, Fischer 344; LE, Long–Evans (outbred); LEW, Lewis; SAB, Sabra (outbred); SD, Sprague–Dawley (outbred); WAG, Wistar Albino Glaxo (WAG/GSto); WIS, Wistar (outbred); WKY, Wistar Kyoto. Genealogical origins of all inbred rat strains can be found at http://www.informatics.jax.org/bin/strains/search.
Other Abbreviations: CD, colorectal distention; CFA, complete Freund’s adjuvant; FJ, flinch–jump test; FT, formalin test; HP, hot-plate test; i.c.v., intracerebroventricular, i.p., intraperitoneal; NT, sciatic and saphenous nerve transection; TF, radiant heat tail-flick test; TRH, thyrotropin-releasing hormone; TW, hot water tail-immersion/withdrawal test.
Only studies with significant strain differences are reported. Excluded are studies involving selected lines [including the spontaneously hypertensive rat (SHR)] and mutants.
Morphine analgesia was significantly attenuated by pretreatment with p-chlorophenylalanine in SD, but not F344 rats.
Clonidine analgesia was naloxone-reversible in SD rats but naloxone-insensitive in WKY rats.
F344 rats also developed increased conditioned analgesia to footshock relative to SD rats.