PMID: 9166759Jun 1, 1997Paper

Heterogeneity of beta-adrenoceptors in guinea-pig brain: radioligand binding and cyclic nucleotide generation

Journal of Neurochemistry
K E NeilS P Alexander

Abstract

In this report, we have examined the radioligand binding and second messenger signalling characteristics of beta-adrenoceptors in the guinea-pig brain. [125I]-Iodocyanopindolol ([125I]ICYP)-labelled sites in the cerebellum and cerebral cortex were of similar densities (Bmax 34 and 24 fmol x mg(-1)) and affinities (K(D) 20 and 55 pM), respectively. Analysis of competition for [125I]ICYP binding in the cerebellum was compatible with the presence of a beta2-adrenoceptor. In this tissue, isoprenaline evoked a cyclic AMP stimulation, and also potentiated cyclic GMP accumulations evoked in the presence of a nitric oxide donor, consistent with mediation via a beta2-adrenoceptor. The [125I]ICYP binding profile in the cerebral cortex did not comply with those previously described for beta-adrenoceptor subtypes, and isoprenaline failed to alter significantly cyclic AMP accumulation in the cerebral cortex, hippocampus, or neostriatum, even in the presence of forskolin or a phosphodiesterase inhibitor. Isoprenaline was also without effect on cyclic GMP accumulation or phosphoinositide turnover in the cerebral cortex. These results suggest that the guinea-pig cerebellum expresses a functional beta2-adrenoceptor coupled to cyclic AMP generat...Continue Reading

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