Epinephrine, phenylephrine, and methoxamine induce infiltrative anesthesia via α1-adrenoceptors in rats

Abstract

Aim: To assess whether epinephrine, phenylephrine, and methoxamine act via certain subtypes of adrenoceptors to exert their local anesthetic activity. Methods: We investigated cutaneous anesthesia from adrenoceptor agonists and/or antagonists in conscious, unanesthetized Sprague-Dawley male rats (weight 200−250 g). Cutaneous anesthesia was evidenced by a block of the cutaneous trunci muscle reflex, which is characterized by reflex movement of the skin over the back produced by twitches of lateral thoracispinal muscles in response to local dorsal cutaneous noxious pinprick. Results: Local infiltration of epinephrine, L-phenylephrine, or methoxamine alone induces cutaneous anesthesia in rats in a dosedependent way. Epinephrine is found to be 19 and 29 times more potent than those of methoxamine and L-phenylephrine, respectively. The cutaneous anesthesia induced by epinephrine, phenylephrine, or methoxamine can be significantly reduced by α 1 -adrenoceptor antagonists (eg, prazosin), α1, α2-adrenoceptor antagonist, α 1A -adrenoceptor antagonist (eg, 5-methylurapdil), α 1B -adrenoceptor antagonist (eg, chloroethylclonidine), or α 1D -adrenoceptor antagonist (eg, BMY7873). Conclusion: Our results indicate that epinephrine, phenylephrine and methoxamine all act mainly via mixed subtypes of α 1 -adrenoceptors to induce cutaneous anesthesia in the rat.

Comparison of Adrenaline and Dexmedetomidine in Improving the Cutaneous Analgesia of Mexiletine in Response to Skin Pinpricks in Rats

“…It may be that the different mechanisms of action of the 2 adjuvants lead to the differences. In our study, subcutaneous Adr at 13.66 μmol showed 50.0% blockade (% MPE), comparable to previous results [26], that is, Adr itself could induce cutaneous anesthesia via mixed subtypes of α 1 -adrenoceptors [27].…”

Propranolol combined with dopamine has a synergistic action in intensifying and prolonging cutaneous analgesia in rats

“…Another result was the first to directly 230 demonstrate that the addition of dopamine to propranolol elicited 231 a synergistic effect of cutaneous analgesia. These results are similar Dose ( µmol/kg) showed that subcutaneous injection of norepinephrine and 241 epinephrine induced dose-dependent cutaneous analgesia in rats 242 [29,44]. This produces the possibility that dopamine as well as 243 epinephrine may have local anesthetic activity in its own right.…”

Organization of sensory input to the nociceptive‐specific cutaneous trunk muscle reflex in rat, an effective experimental system for examining nociception and plasticity

“…Aspects of the CTM and CTMR organization make this system enticing for use as a model to study 1) nociception and anesthesiology; 2) plasticity of primary afferents, motoneurons, and the propriospinal system; and 3) reactions to spinal cord injury/disease and treatment. The CTMR has already proved to be highly useful as a monitor for the progress and extent of sensory neuron axonal collateral sprouting and motoneuron axonal regeneration (see, e.g., Diamond et al, ; Griffin et al, ), for the recovery of function after dorsal root injuries (Jiang et al, ) and spinal cord injuries (SCI) and treatments (Blight, ; Blight et al, ; Borgens et al, , ; Borgens and Bohnert, ; Tansey et al, ), and as a readout for anesthesiological experimentation (Binshtok et al, ; Colvin et al, ; Duarte et al, ; Gerner et al, ; Khan et al, ; Lim et al, ; Mujenda et al, ; Shieh et al, ; Wang et al, ; Yoshitomi et al, ).…”