HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Shen, K Z Articles by Johnson, S W Search for Related Content PubMed PubMed Citation Articles by Shen, K Z Articles by Johnson, S W

Department of Physiology and Pharmacology, Oregon Health Sciences University, Portland 97201, USA.

1. Patch pipettes were used to record whole-cell currents under voltage clamp in substantia nigra zona reticulata (SNR) neurones in the rat midbrain slice. Bipolar electrodes evoked synaptic currents mediated by glutamate (EPSCs) and GABAA receptors (IPSCs). 2. Baclofen reduced the amplitude of IPSCs by 48% at its IC50 value of 0.60 microM. The GABAB antagonist CGP 35348 blocked this effect with a Kd value estimated by Schild analysis of 5 microM. 3. Adenosine reduced IPSCs by 48% at its IC50 value of 56 microM. Adenosine agonists reduced IPSCs with the following rank order of potency: CPA (N6-cyclopentyladenosine) > R-PIA (R(-)N6-(2-phenylisopropyl)adenosine) > CHA (N6-cyclohexyladenosine) = NECA (5'-N-ethylcarboxamidoadenosine) > 2-CADO (2-chloroadenosine) > adenosine. Schild analysis yielded a Kd value of 0.4 nM for antagonism of CPA by the adenosine A1 receptor antagonist DPCPX (8-cyclopentyl-1,3-dipropylxanthine). 4. Both baclofen and adenosine reduced the magnitude of paired-pulse depression of IPSCs, and neither blocked currents evoked by GABA, which was pressure-ejected from micropipettes. 5. Glutamate EPSCs were reduced by baclofen (IC50 = 0.78 microM) and adenosine (IC50 = 57 microM). Schild analysis yielded a Kd value of 11 microM for antagonism of baclofen-induced inhibition of EPSCs by CGP 35348. DPCPX (1 microM) completely blocked the inhibitory effects of adenosine (100 microM) and CPA (100 nM) on EPSCs. Neither adenosine nor baclofen reduced inward currents evoked by glutamate which was pressure-ejected from micropipettes. 6. These results show that presynaptic GABAB and A1 receptors reduce glutamate and GABA release from nerve terminals in the SNR.

This article has been cited by other articles:

				F.-W. Zhou, J.-J. Xu, Y. Zhao, M. S. LeDoux, and F.-M. Zhou Opposite Functions of Histamine H1 and H2 Receptors and H3 Receptor in Substantia Nigra Pars Reticulata J Neurophysiol, September 1, 2006; 96(3): 1581 - 1591. [Abstract] [Full Text] [PDF]

				B. Bettler, K. Kaupmann, J. Mosbacher, and M. Gassmann Molecular Structure and Physiological Functions of GABAB Receptors Physiol Rev, July 1, 2004; 84(3): 835 - 867. [Abstract] [Full Text] [PDF]