Modulation of High-Voltage Activated Ca Channels in the Rat Periaqueductal Gray Neurons by m-Type Opioid Agonist

Kim, Chang-Ju, Jeong-Seop Rhee, and Norio Akaike. Modulaand ‘‘low’’ threshold on the basis of the voltage range at tion of high-voltage activated Ca channels in the rat periaqueducwhich they are activated. Low-voltage-activated Ca chantal gray neurons by m-type opioid agonist. J. Neurophysiol. 77: nels are known as T-type Ca channels (Akaike et al. 1989; 1418–1424, 1997. The effect of m-type opioid receptor agonist, DTakahashi and Akaike 1991). High-voltage activated Ala ,N-MePhe,Gly-ol-enkephalin (DAMGO), on high-voltage(HVA) Ca channels could be classified pharmacologically activated (HVA) Ca channels in the dissociated rat periaqueducinto five types: dihydropyridine (DHP)-sensitive L-type tal gray (PAG) neurons was investigated by the use of nystatinchannel; v -conotoxin-GVIA-sensitive Ntype channel; perforated patch recording mode under voltage-clamp condition. v-agatoxin-IVA-sensitive P-type channel; v-conotoxinAmong 118 PAG neurons tested, the HVA Ca channels of 38 MVIIC-sensitive but DHP/v-conotoxin-GVIA/v-agatoxinneurons (32%) were inhibited by DAMGO (DAMGO-sensitive cells) , and the other 80 neurons (68%) were not affected by IVA-insensitive Q-type channel; and resistant R-type chan-