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J Neurophysiol. 1994 Oct;72(4):1561-9.

Glutamate metabotropic receptors increase a Ca(2+)-activated nonspecific cationic current in CA1 hippocampal neurons.

Author information

1
Institut National de la Santé et de la Recherche Médicale U29, Paris, France.

Abstract

1. We studied the currents evoked in CA1 pyramidal neurons by the selective metabotropic glutamate receptor (mGluR) agonist 1S,3R-1-aminocyclopentane-1,3-dicarboxylate (1S,3R-ACPD; 100 microM, 2.30-5 min) with the single-electrode voltage-clamp technique in the continuous presence of tetrodotoxin (1 microM), bicuculline (10 microM), 6-cyano-7-nitroquinoxaline-2,3-dione (15 microM), and D-2-amino-5-phosphonovaleric acid (50 microM) to depress action potentials and synaptic activity. Microelectrodes were filled with 3M CsCl or 2 M Cs2SO4. 2. With CsCl-filled microelectrodes, bath application of 1S,3R-ACPD induced an inward current of -308 +/p 50 (SE) pA amplitude [holding potential (VH -60 mV, n = 12)] associated with a conductance decrease (26.5 +/- 5.6%, P < or = 0.0022, n = 12). The current-voltage (I-V) relation of the 1S,3R-ACPD-induced (difference) current investigated using ramp voltage commands from -130 to +10 mV had a V shape with two reversal potentials: -99.6 +/- 3.4 and -17.5 +/- 3.0 mV (n = 12). 3. In contrast, in the presence of external K+ channel blockers (2 mM Ba2+ and 6 mM Cs+ or 25 mM tetraethylammonium, 6 mM Cs+, and 3 mM 4-aminopyridine), 1S,3R-ACPD also generated an inward current, albeit of smaller amplitude (-114.2 +/- 27.5 pA, P < or = 0.003, VH -60 mV, n = 8). This current was associated with a conductance increase (20.7 +/- 3.1%, P < or = 0.0117, n = 8), decreased linearly with depolarization (from -130 to -60 mV), and reversed polarity at an estimated potential of -20.7 +/- 3.6 mV (n = 8). We refer to this current recorded in the presence of K+ channel blockers as IACPD. 4. In the presence of Cd2+ (200 microM, to block voltage-dependent Ca2+ channels that are readily activated in the presence of K+ channel blockers) and a low Ca2+ concentration (100 microM), IACPD decreased linearly from -130 to +10 mV and reversed polarity at -15.8 +/- 8.5 mV (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS).

PMID:
7823086
DOI:
10.1152/jn.1994.72.4.1561
[Indexed for MEDLINE]

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