Though it has been known for over half a century that interference with the normal activity of septohippocampal neurons can abolish hippocampal theta rhythmicity, definitive answer to question its function remained elusive. To clarify role septal circuits and in location-specific place cells spatial behavior, three drugs were delivered medial septum rats: Tetracaine, local anesthetic; muscimol, GABA-A agonist; gabazine, antagonist. All disrupted oscillatory hippocampus. However, tetracaine...

The firing of rat hippocampal pyramidal cells is determined both by the animal9s location and state EEG. Because cholinergic transmission plays a role in EEG activity, we expected that its modification would alter place cell activity. We therefore investigated effects on activity blocking muscarinic with intracerebroventricular injections scopolamine. Scopolamine reduced rate discharge inside fields spatial coherence fields; outside also showed small increases. After injections, were shifted...

Using a dialysis probe near CA1 hippocampal recording electrodes, we infused nonspecific (scopolamine) and specific (methoctramine, pirenzepine) antagonists of muscarinic cholinergic transmission to determine their effects on the positional firing properties place cells. Both low (0.5 m ) high (2.0 or 3.0 scopolamine significantly decreased in-field rate, increased ratio out-of-field reduced smoothness rate maps, while tending increase rate. Thus, local blockade mimicked seen with...

In this study, microdialysis was performed in the hippocampus of freely behaving rats, and firing pyramidal cells, including place recorded at site probe. For 10-min periods, artificial cerebrospinal fluid (ACSF) system replaced with ACSF containing 50 mM K+ (high solution). Complementary vitro tests determined that such high solution produced an outflow 5% perfused from Application method into CA1 region significantly increased local during both movement sleep. On average, exposures rate...

Repetitive one-per-day seizures induced in otherwise normal rats by the volatile convulsant flurothyl decrease accuracy of locating a hidden goal without changing mean location selection. We now show that an 8-d series such degrades spatial signal carried firing hippocampal pyramidal cells and specifically reduces information conveyed place cell subset cells. This degradation concomitant slowing theta rhythm occur over time courses parallel to development behavioral deficit plausibly account...

Mathematical modeling has shown that it should be possible to determine the electrotonic location of membrane conductance changes in single neurons by analysis associated magnitude alternating-current (AC) input impedance. The form plot change impedance as a function frequency (delta [Zn(f)]) differ for located at different distances from recording/current-injection site. Due axial resistance and capacitance, higher frequencies are attenuated with distance greater degree than lower...

Measurements of membrane impedance using single-electrode intracellular bridge amplifiers may be seriously distorted even at frequencies as low 16 Hz by capacitances associated with the current limiting resistor and electrode. Modifications capacity compensation circuit are outlined, which eliminate much this error, allowing measurements 108 a conventional micropipets high 400 Hz.