Pertussis toxin-sensitive guanine nucleotide-binding protein(S) couple adenosine A1 and 5-hydroxytryptamine1A receptors to the same effector systems in rat hippocampus: biochemical and electrophysiological studies

JM Zgombick, SG Beck, CD Mahle, B Craddock-Royal and S Maayani

Department of Pharmacology, Mount Sinai School of Medicine, City University of New York, New York 10029.

Distinct membrane receptors that elicit similar cellular responses may share elements of signal transduction. In the present study, rat hippocampal adenosine (AD) and 5-hydroxytryptamine (5-HT) receptors were chosen to test this possibility using biochemical and electrophysiological techniques. Responses elicited by the AD receptor that mediates the inhibition of forskolin-stimulated adenylyl cyclase activity in rat hippocampal membranes and hyperpolarization of resting membrane potential (RMP) in rat hippocampal pyramidal cells were characterized and compared, in the same preparation, with those analogous responses elicited by the 5-HT1A receptor. A series of AD agonists including the selective AD A1 agonist (R)- phenylisopropyladenosine [(R)-PIA] inhibited forskolin-stimulated adenylyl cyclase activity in rat hippocampal membranes in a concentration-dependent manner. Cyclopentyltheophylline (CPT), a selective AD A1 antagonist, was a potent, competitive antagonist of this response with a dissociation constant (Kb) of 6 nM (Schild analysis). The rank order of agonist EC50 values and antagonist Kb values, as well as stereoselectivity, are consistent with the classification of this receptor as the AD A1 receptor. Spiperone, a potent 5-HT1A antagonist, competitively antagonized 5-HT-mediated inhibition of forskolin-stimulated adenylyl cyclase activity in rat hippocampal membranes with a Kb value of 14 nM. Intracellular recording techniques revealed that AD, (R)-PIA, 5-HT, and 5- carboxyamidotryptamine (5-CT) elicited concentration-dependent hyperpolarization of RMP within the same hippocampal pyramidal cell. The maximal hyperpolarization obtained for the AD or 5-HT analogs was the same for individual pyramidal cells. CPT and spiperone antagonized the hyperpolarization by (R)-PIA and 5-CT, respectively. Saturating concentrations of spiperone failed to antagonize (R)-PIA-mediated responses and CPT did not block responses elicited by 5-HT in either the biochemical or electrophysiological preparations. The combination of saturating concentrations of 5-HT and (R)-PIA evoked nonadditive biochemical responses relative to those observed with (R)-PIA alone. Similarly, electrophysiological experiments conducted under voltage- clamp conditions demonstrated that maximally effective concentrations of AD and 5-CT exhibited nonadditive behavior. Because the amount of outward current elicited when these agonists were coperfused was significantly less than the algebraic sum of the currents evoked individually by these agents, we infer that a population of AD A1 and 5- HT1A receptors activates a common pool of guanine nucleotide-binding proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

Volume 35, Issue 4, pp. 484-494, 04/01/1989
Copyright © 1989 by American Society for Pharmacology and Experimental Therapeutics

This article has been cited by other articles:

				L. Hu, K. Wada, N. Mores, L. Z. Krsmanovic, and K. J. Catt Essential Role of G Protein-gated Inwardly Rectifying Potassium Channels in Gonadotropin-induced Regulation of GnRH Neuronal Firing and Pulsatile Neurosecretion J. Biol. Chem., September 1, 2006; 281(35): 25231 - 25240. [Abstract] [Full Text] [PDF]

				J. H. Turner, A. K. Gelasco, and J. R. Raymond Calmodulin Interacts with the Third Intracellular Loop of the Serotonin 5-Hydroxytryptamine1A Receptor at Two Distinct Sites: PUTATIVE ROLE IN RECEPTOR PHOSPHORYLATION BY PROTEIN KINASE C J. Biol. Chem., April 23, 2004; 279(17): 17027 - 17037. [Abstract] [Full Text] [PDF]

				E. Papoucheva, A. Dumuis, M. Sebben, D. W. Richter, and E. G. Ponimaskin The 5-Hydroxytryptamine(1A) Receptor Is Stably Palmitoylated, and Acylation Is Critical for Communication of Receptor with Gi Protein J. Biol. Chem., January 30, 2004; 279(5): 3280 - 3291. [Abstract] [Full Text] [PDF]

				J. C. Rekling, G. D. Funk, D. A. Bayliss, X.-W. Dong, and J. L. Feldman Synaptic Control of Motoneuronal Excitability Physiol Rev, April 1, 2000; 80(2): 767 - 852. [Abstract] [Full Text] [PDF]

				P. R. ALBERT, S. J. MORRIS, M. H. GHAHREMANI, J. M. STORRING, and P. M. C. LEMBO A Putative {alpha}-helical G{beta}{gamma}-coupling Domain in the Second Intracellular Loop of the 5-HT1A Receptor Ann. N.Y. Acad. Sci., December 15, 1998; 861(1): 146 - 161. [Abstract] [Full Text] [PDF]

				R. ANDRADE Regulation of Membrane Excitability in the Central Nervous System by Serotonin Receptor Subtypes Ann. N.Y. Acad. Sci., December 15, 1998; 861(1): 190 - 203. [Abstract] [Full Text] [PDF]

				A. J. Barr, L. F. Brass, and D. R. Manning Reconstitution of Receptors and GTP-binding Regulatory Proteins (G Proteins) in Sf9 Cells. A DIRECT EVALUATION OF SELECTIVITY IN RECEPTOR·G PROTEIN COUPLING J. Biol. Chem., January 24, 1997; 272(4): 2223 - 2229. [Abstract] [Full Text] [PDF]

				P. Butkerait, Y. Zheng, H. Hallak, T. E. Graham, H. A. Miller, K. D. Burris, P. B. Molinoff, and D. R. Manning Expression of the Human 5-Hydroxytryptamine[IMAGE] Receptor in Sf9 Cells J. Biol. Chem., August 4, 1995; 270(31): 18691 - 18699. [Abstract] [Full Text] [PDF]