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Effects of Vasodilators Guanethidine, Nicardipine, Nitroglycerin, and Prostaglandin E 1 on Primary Afferent Nociceptors in Humans
Author(s) -
Mashimo Takashi,
Pak Myon,
Choe Huhu,
Inagaki Yoshimi,
Yamamoto Mitsuaki,
Yoshiya Ikuto
Publication year - 1997
Publication title -
the journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.92
H-Index - 116
eISSN - 1552-4604
pISSN - 0091-2700
DOI - 10.1002/j.1552-4604.1997.tb04310.x
Subject(s) - vasodilation , medicine , guanethidine , nociceptor , anesthesia , lidocaine , prostaglandin , nociception , pharmacology , receptor , stimulation
Although vasodilator agents have been used to alleviate the pain of complex regional pain syndromes, the precise mechanism of pain relief is not well known. In this study the effects of various kinds of vasodilators on primary afferent nociceptors were investigated by measuring the thermal pain threshold. Evaluated in the study were the effects of guanethidine (2 mg/mL), nicardipine (0.2 mg/mL), Nitroglycerin (0.3 mg/mL), and prostaglandin E 1 (1 μg/mL) on the cutaneous pain threshold and blood flow at 7‐day intervals in six healthy volunteers. Each aliquot of 0.5 mL of the test vasodilator or lidocaine (10 mg/mL) and saline (control) were intradermally injected at three sites each on both forearms. The pricking‐pain threshold and skin tissue blood flow were determined using a radiant heat—stimulating system and a laser‐Doppler tissue—blood flowmeter, respectively. The pain threshold increased with lidocaine, guanethidine, and nicardipine; remained unchanged with Nitroglycerin; but decreased with prostaglandin E 1 . In contrast, the skin tissue blood flow increased by four to nine times with all vasodilators. These results indicate that the effect of vasodilators on primary afferent nociceptors is not related to the vasodilating effect and may not involve a common mechanism of action for pain relief in complex regional pain syndromes.