Antihyperalgesic activity of a novel synthesized analogue of lidocaine in diabetic rats

Synthesis and biological activities of local anesthetics

Local anesthetics are mainly used in stomatology, ophthalmology, gynecology and surgery to temporarily relieve pain. Local anesthetics act on nerve endings or around nerve trunks, and are combined with specific sodium ion (Na⁺) channel sites on the nerve membrane. They can affect the membrane potential by reducing Na⁺ passage through sodium ion channels, thus blocking the generation and conduction of nerve impulses, reversibly blocking the generation and conduction of sensory nerve impulses. Local anesthetics are used for convenience in local surgical operations and treatments. Herein, we mainly review the research progress on local anesthetics and discuss the important aspects of design, synthesis and biological activity of various new compounds.

Local anesthetics are mainly used in stomatology, ophthalmology, gynecology and surgery to temporarily relieve pain.

Pharmacological profile of N-(2,6-dichlorophenyl)-2-(4-methyl-1-piperidinyl)acetamide, a novel analogue of lidocaine

AIM

N-(2,6-Dichlorophenyl)-2-(4-methyl-1-piperidinyl)acetamide (LIA), a lidocaine analogue, has potential applications in treating neuropathic pain. The aim of this work was to characterize the pharmacological activity of LIA related with central nervous system and cardiovascular activity.

METHODS

Anesthetic effect was tested in guinea pigs and mice. Ambulatory activity, anti-anxiety effect, sodium pentobarbital (PB)-induced hypnosis and pentylenetetrazol (PTZ)-induced seizures test were evaluated in mice to determine the possible central nervous system activity. The cardiovascular activities in vivo and ex vivo were analyzed in rats.

KEY FINDINGS

LIA (2%) presents, similar to lidocaine (2%), anesthetic activity on the corneal reflex, infiltration anesthesia and tail immersion test. LIA (1-100mg/kg, i.p.), similar to lidocaine (1-100mg/kg, i.p.), presents a dose-dependent sedative-hypnotic effect in mice. Both compounds did not produce anti-anxiety activity in mice. LIA did not prevent PTZ-induced seizures. However, LIA itself did not produce seizures at high doses in mice, as lidocaine does. LIA is a vasorelaxant compound for smooth muscle cells and presents hypotensive effect in vivo without increments to the heart rate significantly.

SIGNIFICANCE

High doses of lidocaine produce seizures and vasoconstriction. In this study, we found that LIA shares a similar pharmacological profile as lidocaine's but without the primary adverse effects of seizures and vasoconstriction.

Antinociceptive and antihyperglycemic effects of Melissa officinalis essential oil in an experimental model of diabetes

OBJECTIVE

The efficacy of oral administration of Melissa officinalis essential oil (MOEO) on hyperalgesia was investigated using the formalin test in streptozotocin (STZ)-induced diabetic rats.

MATERIALS AND METHODS

Animals were divided into control, MOEO-treated control (0.01, 0.02 and 0.04 mg/day), diabetic and MOEO-treated diabetic (0.01, 0.02 and 0.04 mg/day) groups. Nociceptive testing was performed on male adult Wistar rats 4 weeks after the onset of hyperglycemia. At the end of the experiment, all rats were weighed and plasma glucose measurements were performed.

RESULTS

Diabetes was associated with significant hyperalgesia during both phases of the formalin test. MOEO (0.04 mg/day) completely reversed hyperalgesia in diabetic rats, while MOEO (0.02 and 0.04 mg/day) caused less intensive nociceptive behaviors during both phases of the test in control rats. MOEO at both high doses restored euglycemia and reduced the body weight of treated diabetic animals compared to untreated diabetic animals. The 0.01-mg dose of MOEO did not alter pain responses in the control or diabetic groups compared to their respective controls.

CONCLUSIONS

This study shows that chronic administration of MOEO displays efficacy in an experimental model of diabetic hyperalgesia. MOEO may therefore show promise as a treatment for painful diabetic neuropathy.