PT - JOURNAL ARTICLE AU - E Tanaka AU - RA North TI - Opioid actions on rat anterior cingulate cortex neurons in vitro AID - 10.1523/JNEUROSCI.14-03-01106.1994 DP - 1994 Mar 01 TA - The Journal of Neuroscience PG - 1106--1113 VI - 14 IP - 3 4099 - http://www.jneurosci.org/content/14/3/1106.short 4100 - http://www.jneurosci.org/content/14/3/1106.full SO - J. Neurosci.1994 Mar 01; 14 AB - Intracellular recordings were made from layer V pyramidal neurons in slices of rat anterior cingulate cortex, using electrodes that contained potassium methylsulfate and biocytin. [Met5]enkephalin (300 nM to 30 microM) reversibly reduced the amplitude of EPSPs evoked by stimulation of the subcortical white matter; the half-maximal concentration was about 800 nM. These EPSPs were blocked by (+/-)-2- amino-5-phosphonovaleric acid and 6-cyano-7-nitroquinoxaline-2,3-dione. [Met5]enkephalin also reduced the amplitude of bicuculline-sensitive IPSPs evoked by stimulation within layer V; the half-maximal concentration was about 60 nM. Both these actions of [Met5]enkephalin were mimicked by the delta-selective agonist DPDPE (Tyr-D-Pen-Gly-Phe-D- Pen) but not by the mu-selective agonist DAMGO (Tyr-D-Ala-Gly-MePhe-Gly- ol); they were blocked by the delta-selective antagonist naltrindole (apparent dissociation constant of about 0.3 nM) but not by the mu- selective antagonist CTOP (D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2). [Met5]enkephalin did not change the amplitudes of depolarizations evoked by direct application of glutamate or hyperpolarizations evoked by direct application of muscimol (at -55 mV). Fifty percent (22 of 45) of pyramidal cells were hyperpolarized by [Met5]enkephalin; this resulted from an increase in potassium conductance, and it was mimicked by DPDPE and blocked by naltrindole. Five of seven nonpyramidal cells were hyperpolarized by [Met5]enkephalin; this was mimicked by DAMGO and blocked by CTOP.(ABSTRACT TRUNCATED AT 250 WORDS)