Intracellular Recording of Potassium in Neurons of the Motor Cortex of Awake Cats Following Extracellular Applications of Acetylcholine

Intradendritic recordings from neurons of motor cortex of cats

Journal of Neurophysiology ◽

10.1152/jn.1984.51.5.925 ◽

1984 ◽

Vol 51 (5) ◽

pp. 925-938 ◽

Cited By ~ 32

Author(s):

C. D. Woody ◽

E. Gruen ◽

K. McCarley

Keyword(s):

Motor Cortex ◽

Input Resistance ◽

Resting Potential ◽

Single Neurons ◽

Spike Generation ◽

Pressure Injection ◽

Potential Spike ◽

Normal Functional ◽

Awake Cats ◽

In Cells

The properties of neuronal spike potentials ranging from 20 to 60 mV in size were studied in stable recordings made from the motor cortex of unanesthetized, unparalyzed cats. Histologic evidence that injection of horseradish peroxidase (HRP) was confined to single neurons and appropriately high levels of potassium measured with K+ ion-sensitive electrodes indicated that these recordings were obtained from single, intracellularly penetrated neurons. Pressure injection of small volumes of 4% HRP in 1 M KC1, intracellularly, was characteristically associated with transient increases in spike size and decreases in input resistance. Recoveries of HRP-filled dendritic processes without filling of somata were obtained from penetrations giving spikes smaller than the recorded resting potential (spike-undershoot recordings). Recordings with dendritic recoveries had higher input resistances and showed greater increases in spike size during pressure injection than did recordings with both somata and dendrites recovered. The activity in response to a weak click elicited in cells with spike potentials between 20 and 40 mV was as great or greater than that elicited in cells with larger spike potentials or in extracellularly recorded units. We conclude that many stable spike-undershoot recordings of neurons of the motor cortex of awake cats reflect penetrations of dendritic processes as opposed to injury because they show a) a normal functional response to weak auditory stimuli delivered over periods of many minutes, b) a reversible increase in spike size during pressure injection of small volumes of HRP in KC1 consistent with penetration of a cable remote from the site of spike generation, and c) the frequent recovery of HRP-marked dendrites without somata.

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Activity of the Motor Cortex During Scratching

Journal of Neurophysiology ◽

10.1152/jn.00050.2005 ◽

2006 ◽

Vol 95 (2) ◽

pp. 753-765 ◽

Cited By ~ 1

Author(s):

Mikhail G. Sirota ◽

Galina A. Pavlova ◽

Irina N. Beloozerova

Keyword(s):

Motor Cortex ◽

Hind Limb ◽

Pyramidal Tract ◽

Average Depth ◽

Simple Correlation ◽

Population Activity ◽

Ankle Muscles ◽

Pyramidal Tract Neurons ◽

Awake Cats ◽

Stimulation Of

In awake cats sitting with the head restrained, scratching was evoked using stimulation of the ear. Cats scratched the shoulder area, consistently failing to reach the ear. Kinematics of the hind limb movements and the activity of ankle muscles, however, were similar to those reported earlier in unrestrained cats. The activity of single neurons in the hind limb representation of the motor cortex, including pyramidal tract neurons (PTNs), was examined. During the protraction stage of the scratch response, the activity in 35% of the neurons increased and in 50% decreased compared with rest. During the rhythmic stage, the motor cortex population activity was approximately two times higher compared with rest, because the activity of 53% of neurons increased and that of 33% decreased in this stage. The activity of 61% of neurons was modulated in the scratching rhythm. The average depth of frequency modulation was 12.1 ± 5.3%, similar to that reported earlier for locomotion. The phases of activity of different neurons were approximately evenly distributed over the scratch cycle. There was no simple correlation between resting receptive field properties and the activity of neurons during the scratch response. We conclude that the motor cortex participates in both the protraction and the rhythmic stages of the scratch response.

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