RAPID COMMUNICATION Neuromodulation of Dendritic Action Potentials

Hoffman, Dax A. and Daniel Johnston. Neuromodulation of denM E T H O D S dritic action potentials. J. Neurophysiol. 81: 408–411, 1999. The Hippocampal slices (400 mm thick) from Sprague-Dawley rats, extent to which regenerative action potentials invade hippocampal 5–8 wk old, were prepared as described previously (Hoffman CA1 pyramidal dendrites is dependent on both recent activity and and Johnston 1998). Recordings were made at 31–357C using distance from the soma. Previously, we have shown that the amplian automatic temperature controller (Warner Instrument, Hamden, tude of back-propagating dendritic action potentials can be inCT). The following were included in the external solution (as creased by activating either protein kinase A (PKA) or protein described in Hoffman and Johnston 1998) to block synaptic transkinase C (PKC) and a subsequent depolarizing shift in the activamission (in mM): 50 D,L-2-amino-5-phosphonovaleric acid (D,Ltion curve for dendritic K/ channels. Physiologically, an increase APV; RBI), 20 MK-801 (RBI), 10 6-cyano-7-nitroquinoxalinein intracellular PKA and PKC would be expected upon activation 2,3-dione (CNQX; RBI), 10 bicuculline (Sigma), and 10 picroof b-adrenergic and muscarinic acetylcholine receptors, respectoxin (Sigma). Isoproterenol (1–2 mM, Sigma), carbachol (1 mM, tively. Accordingly, we report here that activation of either of these Sigma), 6-Cl-PB (10 mM, Sigma), and H7 (300 mM, Sigma) were neurotransmitter systems results in an increase in dendritic actiondissolved directly into the bath solution with the addition of 1 mM potential amplitude. Activation of the dopaminergic neurotransmitascorbate. Whole cell recording pipettes (8–14 MV) were filled ter system, which is also expected to raise intracellular adenosine with (in mM) 120 KMeSO4, 20 KCl, 10 N-2-hydroxyethylpipera3*,5 *-cyclic monophosphate (cAMP) and PKA levels, increased zine-N *-2-ethanesulfonic acid (HEPES), 0.2 ethylene glycolaction-potential amplitude in only a subpopulation of neurons bis(b-aminoethyl ether)-N,N,N*,N *-tetraacetic acid (EGTA), 2 tested. MgCl2 , 4 Na-ATP, 0.3 tris(hydroxymethyl)aminomethane guanosine triphosphate (Tris-GTP), and 14 phosphocreatine (pH 7.25