G1-0-7 Infiltration anesthesia in guinea pig`s wheals

G.1.0.7
Infiltration anesthesia in guinea pig’s wheals
PURPOSE AND RATIONALE
Based on earlier work by McIntyre and Sievers
(1937) and Sievers and McIntyre AR (1938), the use
of intracutaneous wheals in guinea pigs was recommended by Bülbring and Wajda (1945). This method
has become a standard operating procedure for testing
local anesthetics.
PROCEDURE
Adult guinea pigs of either sex weighing 250–300 g
are chosen. On the day preceding the experiment the
hair on the back is clipped and two areas of 4–5 cm
diameter are shaved. This produces a certain amount
of irritation which disappears overnight. The sensitivity of the skin is greatest in the midline and slightly
more so in the front than in the back area. For this
reason each concentration of a local anesthetic must
be tested in both areas. Six tests using three guinea
pigs can be performed simultaneously. The doses of
local anesthetics are always injected intracutaneously
in 0.1 ml saline. Three guinea pigs receive one dose
in the front area and another dose in the back area; the
size of the wheal is marked with ink. One side is used
for the test preparation, the other side for the standard
(e.g., 1% butanilicaine). The reaction to pin prick is
tested 5 min after injection in the following way. After observing the animal’s normal reaction to a prick
applied outside the wheal, six pricks are applied inside the wheal and the number of pricks is counted to
which the guinea pig fails to react. The pricks are
applied at intervals of about 3–5 sec. Six pricks are
applied every 5 min for 30 min. Having completed
the test on 3 guinea pigs, the same solutions are injected into 3 other guinea pigs, but the solution which
was used for the front is now used for the back area
and vice versa.
EVALUATION
The number of times the prick fails to elicit a response during the 30 min period is added up, and the
sum, out of possible 36, gives an indication of the degree of anesthesia. Using various doses, doseresponse curves can be established. For time-response
curves, the prick tests are repeated every 10 min.
Half-life times are calculated as the time, when after
complete anesthesia 3 out of 6 pricks elicit again a response (Ther 1953 a and b).
MODIFICATIONS OF THE METHOD
The test can also be used to study the influence of
vasoconstrictors, such as adrenaline.
REFERENCES
Bülbring E, Wajda I (1945) Biological comparison of local anesthetics. J Pharmacol Exp Ther 85:78–84
Camougis G, Takman BH (1971) Nerve and nerve-muscle
preparations (as applied to local anesthetics) In: Schwartz
A (ed) Methods in Pharmacology, Vol 1, pp 1–40. Appleton-Century-Crofts, Educational Division, Meredith Corp.,
New York
McIntyre AR, Sievers RF (1937) The toxicity and anaesthetic
potency of some alkoxy benzoates and related compounds.
J Pharmacol Exp Ther 61:107–120
Muschaweck R, Rippel R (1974) Ein neues Lokalanästhetikum
(Carticain) aus der Thiophenreihe. Prakt Anästh 9:135–146
Muschaweck R; Habicht R, Rippel R (1986) Lokalanaesthetica. In: Ehrhart G, Ruschig H (eds) Arzneimittel.
Entwicklung – Wirkung – Darstellung. Verlag Chemie
GmbH, Weinheim. pp 1–44
Sievers RF, McIntyre AR (1938) The toxicity and anesthetic
potency of some new benzoyl derivatives. J Pharmacol Exp
Ther 62:252–262
Ther L (1953 a) Zur Prüfung der lokalanästhetischen Wirkung
des Pantocain und des 4-n-Butylaminosalicylsäuredimethylaminoaethylesters im Tierversuch. Arzneim Forsch 3:
345–348
Ther L (1953 b) Über ein neues Leitungsanaesthetikum der
“Nirvanin”-Reihe mit großer Entgiftungsgeschwindigkeit
(Hostacain). Naunyn Schmiedeberg’s Arch exper Path
Pharmakol 220:300–316
Wiedling S (1964) Xylocaine. The pharmacological basis of its
clinical use. Almqvist & Wiksell, Stockholm, Göteborg,
Uppsala. pp 27–46