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EFFECTS OF LOCAL ANESTHETICS ON SYNAPTIC TRANSMISSION OF THE BULLFROG SYMPATHETIC

GANGLION

KOHSUKE SOMEI , HIROMI SAWANO , JUNICHI YODA , TADASI SATO AND TAKASHI A. SUZUKI

Dept. Oral Physiol., Sch. Dent., Iwate Med. Univ., Morioka Iwate 020

The effects of local anesthetics, such as lidocaine (Lido), procaine (Pro),

tetracaine (Tetra) and dibucaine (Dibu), were studied on the synaptic transmission

in the isolated frog sympathetic ganglia by means of extracellular recording.

Ganglia were exposed to solutions in a series of graded reductions in

concentration of the local anesthetics while recording the amplitudes of the

postganglionic compound action potential. The amplitudes of the compound action

potential relative to those in a normal Ringer's were then plotted as a logarithmic

function of the local anesthetic concentration. The blocking potencies of the local

anesthetics tested were in the following order: Dibu>Tetra>Pro>Lido.

After analyzing the blocking potency for the impulse conduction and synaptic

transmission, the mode of blockade for Lido was analyzed by plotting the dose-

inhibition curve using 4-aminopyridine (4-AP). The blocking potency of Lido for the

synaptic transmission was 5 times higher than that for the impulse conduction, and

its blocking mode was found to be noncompetitive. Lido did not interfere in the 4-

AP-induced augmentation of the synaptic transmission. Lido probably acts on the

allosteric site of the nicotinic receptor in the postganglionic neurons.

LOCALIZATION OF ADRENERGIC RECEPTORS IN THE RAT BRAIN: AN IMMUNOCYTOCHEMICAL ANALYSIS USING ANTISERUM AGAINST ADRENERGIC RECEPTORS.

IAKIO WANAKA, 2TAKESHI MURAKAMI, IMASAYASU MATSUMOTO, ISHOTARO YONEDA, ITAKENOBU KAMADA, 3CRAIG C. MALBON, and 2MASAYA TOHYAMA, lIST. DEPT. of INTERNAL MEDICINE, 22ND. DEPT. of ANATOMY OSAKA UNIV. MED. SCH., 4-3-57 NAKANOSHIMA, KITAKU OSAKA 530, JAPAN, 3STATE UNIV, of NEW YORK at STONY BROOK, NY, U.S.A.

Catecholamines are well known to be involved in various functions inthe central nervous system. In order to understand the functions of the catecholaminergic neuro systems, the localization of the receptors must be elucidated. Previous studies on this issue have been mainly carried out using in vitro autoradiographic methods. In the present study, we examined the localization of the adrenoreceptors in the rat brain by means of immunocytochemistry with antiserum against purified 82-adrenoreceptors. The antiserum was raised in rabbits immunized with 82-adrenoreceptors purified from guinea pig lung (specific activity is greater than 0.5 nmol/ mg protein). The adrenoreceptor- like immunoreactive (ADR-IR) structures were light-microscopically observed on the surface of the soma or the proximal part of their processes, or within the cytoplasm as a dotted appearance. They were widely but unevenly distributed in the rat brain. The most densely distributed areas were the hypothalamus (paraventricular n., supraoptic n., periventricular zone) and n. tractus solitarii. The cerebral cortex, olfactory tubercle and hippocampus contained a number of ADR-IR cells. The cranial motor and sensory nuclei, reticular formation and raphe nuclei also contained a moderate number of ADR-IR cells. Purkinje cells of the cerebellum were labeled by the antiserum. On the other hand, the striatum and the thalamus had no or only a few ADR-IR structures. Subsequent immunoelectron microscopic analysis in the hypothalamus revealed that ADE-IR structures were mainly associated with the postsynaptic membrane or localized within the cytoplasm. Thus, the present study demonstrates the target cells of the catecholaminergic fibers in various brain regions.