Involvement of 5-HT1A/1B receptors in the antinociceptive effect of paracetamol in the rat formalin test.

The mechanism of analgesic action of paracetamol (acetominophen) remains still unknown. However, a relationship between serotonergic system and the effect of paracetamol has been previously demonstrated. The serotonin activity in the brainstem is primarily under the control of 5-HT1A somatodendritic receptors, although some data also suggest the involvement of 5-HT1B receptors. To determine whether the 5-HT1A and 5-HT1B receptors are involved in the antinociceptive effect of paracetamol, we evaluated the effect of paracetamol (0.125-1 g/kg i.p.) followed by different antagonists [WAY 100,635 (0.8 mg/kg s.c.) and SB 216,641 (0.8 mg/kg s.c.)] or agonists [8-OH-DPAT (0.125 mg/kg s.c.) and CP 93,129 (0.125 mg/kg s.c.)] of 5-HT1A and 5-HT1B receptors, respectively, in the rat model of formalin-induced pain. We demonstrated that paracetamol administration showed a dose-dependent antinociceptive effect in the formalin test. WAY 100,635 (5-HT1A antagonist) induced an increase in the antinociceptive effect of paracetamol at 250 mg/kg doses. Conversely, 8-OH-DPAT (5-HT1A agonist) decreased the antinociceptive effect of paracetamol at 500-1000 mg/kg doses. However, SB216641 (5-HT1B antagonist) modified weakly the antinociceptive effect of paracetamol at 250 mg/kg doses and CP 93,129 (5-HT1B agonist) not produce a clear effect in the antinociceptive effect of paracetamol. These results suggest that the antinociceptive effect of paracetamol can be enhanced mainly by compounds having 5-HT1A antagonist properties in the formalin test and maybe by 5-HT1B receptors antagonists.

Fatty acid composition and sensory traits of beef fed palm oil supplements.

This study measured the effect of replacing dietary fat from an animal source with palm oil supplements on the intramuscular fatty acid profile and sensory quality traits of the meat from young bulls. Thirty-six entire male Friesian calves (mean age=6.8±1.1 months, mean live weight=162.5±28.6kg) were assigned to one of four isoenergetic (1.03 MFU/kg DM) and isoproteinic (15.5% CP) diets, that differed in their fat additives: (D1) lard-tallow mix (control); (D2) hydrogenated palm oil fatty acids (PFA); (D3) calcium salt of partially hydrogenated PFA, and (D4) calcium salt of the fatty acid distillate from palm oil. Bulls (mean live weight=391.3±30.3kg) were slaughtered under commercial conditions and sensory tests were performed to evaluate the effects of the four diets and ageing time (1, 10, and 21d). Only the proportions of C16:0 and C18:0 were significantly affected by the palm oil dietary supplement. Ageing time affected grass odour, tenderness, juiciness, fibrosity, liver flavour, and acid flavour. Nevertheless, palm oil supplements did not negatively alter the organoleptic characteristics of the meat.

Effect of social dominance on the meat quality of young Friesian bulls.

This study examined whether social status of the animals influenced the productive, morphological, physiological, and meat quality parameters in young Friesian bulls. The social dominance index (SDI) was estimated by direct observation of the dominance relationships among animals living in a feedlot. Thirty young bulls were divided into three groups based on their social status as assessed by SDI. The social status of the animals had a small effect on daily growth rate, but did not affect carcass or meat quality parameters. Physiological measures of stress were also unaffected by the animals' social status.