Heterogeneity of presynaptic calcium channels revealed by species differences in the sensitivity of synaptosomal 45Ca entry to ω-conotoxin

Suszkiw, Janusz B.; Murawsky, M.; Fortner, R.C.

doi:10.1016/0006-291x(87)91576-2

Cited by 68 publications

(12 citation statements)

References 9 publications

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“…Ca2+ influx into rat brain synaptosomes stimulated by potassium depolarization was inhibited by w-CTX at 300 nM to 8210 of the control level, whereas [3H]DA release from rat striatal slices was inhibited by relatively low con centrations of w-CTX, in a concentration-dependent man ner. Furthermore, there were species differences in the sensitivity of synaptosomal Ca" influx to w-CTX, as noted previously (21). Dissociation between the inhibitory effects of w-CTX on Ca 21 influx and neurotransmitter re lease has been reported previously in rats (22,41).…”

Section: Discussionsupporting

confidence: 77%

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Neuropharmacological Characterization of Voltage-Sensitive Calcium Channels: Possible Existence of Neomycin-Sensitive, ω-Conotoxin GVIA- and Dihydropyridines-Resistant Calcium Channels in the Rat Brain

Yamada

Teraoka

Morita

et al. 1993

Japanese Journal of Pharmacology

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ABSTRACT-We attemped to characterize the functional roles of subtypes of voltage-sensitive calcium channels in the brain. The maximal number of [125I]w-conotoxin GVIA (w-CTX) binding sites in rat brain associated with N-type calcium channels (N-channels) was approximately 10 times more than that of [3H] PN200-110 associated with L-type calcium channels (L-channels). [3H]dopamine (DA) release from rat striatal slices. The L-channel antagonists had no effect on either Ca 21 influx or [3H]DA release. These results suggest that DA release in the striatum is regulated by Ca 21 influx through N-channels located in presynaptic nerve terminals, and that the most of the Ca 21 influx in rat brain appears to be governed by neomycin-sensitive, w-CTX and DHP-resistant calcium channels.

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Section: Discussionsupporting

confidence: 77%

“…With regard to Ca 21 influx, however, results vary, depending on the source of the brain tissue. For ex ample, w-CTX inhibits potassium-stimulated Ca 21 influx into chick brain synptosomes in a dose-dependent man ner, while much higher concentrations of w-CTX have only a marginal effect on Ca 21 influx into rat brain synap tosomes (21,22).…”

mentioning

confidence: 94%

Neuropharmacological Characterization of Voltage-Sensitive Calcium Channels: Possible Existence of Neomycin-Sensitive, ω-Conotoxin GVIA- and Dihydropyridines-Resistant Calcium Channels in the Rat Brain

Yamada

Teraoka

Morita

et al. 1993

Japanese Journal of Pharmacology

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“…When added cumulatively on steady-state baseline, Ac.Cr caused a vasoconstrictor effect, which remained unchanged in the presence of phentolamine, an a-adrenoceptor antagonist, 25 ruling out the involvement of a-adrenoceptor stimulation. Under similar experimental conditions, the fractions were without a contractile effect on the baseline tension, which indicates that apparently both the fractions are devoid of such effect, although an endothelialdependent effect, if any, cannot be ruled out.…”

Section: Discussionmentioning

confidence: 87%

Blood Pressure-lowering and Vascular Modulator Effects of Acorus calamus Extract Are Mediated Through Multiple Pathways

Shah

Gilani²

2009

Journal of Cardiovascular Pharmacology

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This investigation was aimed to provide a pharmacologic basis to the medicinal use of Acorus calamus in cardiovascular disorders. In normotensive anesthetized rats, crude extract of Acorus calamus and its ethylacetate and nHexane fractions caused a fall in mean arterial pressure. In rabbit aorta rings, crude extract was more potent against high K (80 mM), ethylacetate against phenylephrine (1 microM), whereas nHexane fraction was equipotent against both precontractions. Crude extract exhibited a vasoconstrictor effect on baseline. Pretreatment of aortic rings with crude extract and its fractions shifted Ca concentration-response curves to the right, similar to verapamil. Crude extract and ethylacetate fraction suppressed phenylephrine peak formation in Ca-free medium. In rat aorta preparations, crude extract exhibited endothelium-independent relaxation with a vasodilatory effect against high K. nHexane fraction caused an endothelium-dependent Nomega-nitro-l-arginine methyl ester-sensitive vasorelaxant along with ryanodine-sensitive vasoconstrictor effect on baseline tension and partially inhibited high K, although ethylacetate fraction caused an endothelium-independent relaxant and endothelium-dependent vasoconstrictor effect. These data indicate that crude extract possesses a combination of effects, relaxant effects mediated possibly through Ca antagonism in addition to a nitric oxide pathway, although the associated vasoconstrictor effects may be meant by nature to offset excessive vasodilatation, thus providing a pharmacologic rationale to its cardiovascular medi-cinal uses.

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“…Nor does it affect all neuronal Ca channels, as T-type channels are insensitive to ~o-conotoxin as are Ca channels in Aplysia bag-cell neurons (McCleskey et al, 1987). Different levels of inhibition by oJ-conotoxin of Ca channels in synaptosomes derived from different species has been observed (Suszkiw, Murawsky & Fortner, 1987). Conceivably this could be due to different amounts of the susceptible channels.…”

Section: Toxins and Natural Compounds As Pharmacological Probes Of Camentioning

confidence: 99%

Calcium channels: Molecular pharmacology, structure and regulation

1988

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Heterogeneity of presynaptic calcium channels revealed by species differences in the sensitivity of synaptosomal 45Ca entry to ω-conotoxin

Cited by 68 publications

References 9 publications

Neuropharmacological Characterization of Voltage-Sensitive Calcium Channels: Possible Existence of Neomycin-Sensitive, ω-Conotoxin GVIA- and Dihydropyridines-Resistant Calcium Channels in the Rat Brain

Neuropharmacological Characterization of Voltage-Sensitive Calcium Channels: Possible Existence of Neomycin-Sensitive, ω-Conotoxin GVIA- and Dihydropyridines-Resistant Calcium Channels in the Rat Brain

Blood Pressure-lowering and Vascular Modulator Effects of Acorus calamus Extract Are Mediated Through Multiple Pathways

Calcium channels: Molecular pharmacology, structure and regulation

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