The relation between the effect of a subhypnotic dose ofthiopental on claw pain threshold in rats and adrenalin, noradrenalin and dopamine levels
Mehmet Aksoy1, Ali Ahiskalioglu1, Ilker Ince1, Mine Celik1, Aysenur Dostbil1, Renad Mammadov2, Adnan Yilmaz3, Halis Suleyman4
1Department of Anesthesiology and Reanimation, Faculty of Medicine, Ataturk University,
2Department of Pharmacology, Faculty of Medicine, Ataturk University, Erzurum
3Department of Biochemistry, Faculty of Medicine, Recep Tayyip Erdogan University, Rize,
4Department of Pharmacology, Faculty of Medicine, Recep Tayyip Erdogan University,
INTRODUCTION: Thiopentals are the most widely used barbiturate-type general anesthetic agent in animal experiments. AIM: To investigate the effect of a subhypnotic dose of TPS on the claw pain threshold in rats and evaluated its relationship with endogenous adrenalin (ADR), noradrenalin (NDR) and dopamine (DOP) levels. MATERIALS-METHODS: Intact animals were divided: 15 mg/kg TPS (TS), 0.3 mg/kg ADR+15 mg/kg TPS (ATS) or 0.3 mg/kg ADR alone (ADR). Adrenalectomized animals were divided: 15 mg/kg TPS (A-TS), 0.3 mg/kg ADR+15 mg/kg TPS (A-ATS) or 0.3 mg/kg ADR alone (A-ADR) (n=10, for each group). Claw pain threshold and blood ADR, NDR and DOP levels measured. RESULTS: Claw pain threshold in the TS group fell 7.1 g compared to normal. However, in the ATS rat group the claw pain threshold rose by 15.5 g, and by 14.3 g in the ADR group. In the A-TS group, too, the pain threshold rose by 1.5 g compared to normal, by 14.7 g in the A-ATS group and 11.7 g in the A-ADR group. ADR alone in adrenalectomized rats established significant analgesia at a level of 41.8% (Table I). TPS reduced plasma ADR levels in intact rats (P<0.01), but caused nosignificant change in NDR and DOP levels. However, ADR levels in rats given ADR alone were significantly higher compared to the ATS group, in which it was given together with TPS (P<0.01). In addition, while no plasma ADR level could be measured in adrenalectomized rats, NDR and DOP levels exhibited a significant increase compared to those in the intact rats. TPS caused no significant change in ADR levels given externally (Table II). CONCLUSION: TPS induced hyperalgesia by reducing ADR production in rats without affecting NDR and DOP production.TPS needs to be applied together with ADR in order to establish its analgesic effect in general anesthesia.
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