Action Potentials Of Single Neurons Research Articles

Effects of benzodiazepines and pentobarbitone on the GABA-ergic recurrent inhibition of hippocampal neurons

The actions of benzodiazepines and pentobarbitone on GABA-mediated recurrent inhibition of hippocampal pyramidal neurons were investigated in the immobilized unanaesthetized cat. Extracellular action potentials of single neurons were recorded in regions CA1 or CA2 with 4 M NaCl-containing glass micropipettes. Bicuculline (0.1 mg/kg i.v.) reduced the period of inhibition induced by stimulation of the fimbria and the septum, but fludiazepam and diazepam (0.3–1.0 mg/kg i.v.) and pentobarbitone (15–30 mg/kg i.v.) prolonged the inhibition. The prolongation produced by these compounds was antagonized by the administration of bicuculline (0.3 mg/kg i.v.). The results suggest that these two classes of compounds potentiate GABA-mediated recurrent inhibition in hippocampal neurons in a similar way.

Direct inhibitory synaptic linkage of pontomedullary reticular burst neurons with abducens motoneurons in the cat

1. Unit spikes of burst neurons were extracellularly recorded in the pontomedullary reticular formation of the cat. These neurons were identified by their burst activity coincident with the quick inhibitory phase of the contralateral abducens nerve during vestibular nystagmus and their antidromic activation from the contralateral abducens nucleus. 2. When the extracellular field potentials in and near the abducens nucleus were triggered by spikes of a contralateral burs neuron, the averaged potential consisted of an early di- or triphasic spike and a late slow positive wave. The early spike was an action current caused by impulses conducting along the axon of the burst neuron. 3. The action potentials of a contralateral burst neuron. 3. The action potentials of a contralateral burst neuron were employed to trigger a post-spike average of the membrane potential of abducens motoneurons. Then unitary IPSPs with monosynaptic latencies were revealed. This provided direct evidence that the burst neurons are inhibitory in nature. The amplitudes of unitary IPSPs ranged from 18 to 220 mu V. Each inhibitory burst neuron branched widely in the abducens nucleus and was estimated to make inhibitory connections with approximately 60% of the motoneuron pool. 4. The post-spike average of compound potentials of the abducens nerve triggered by action potentials of contralateral single inhibitory burst neurons revealed inhibition of spike activity with latencies and time courses compatible with those of unitary IPSPs in motoneurons. The inhibition was observed with all inhibitory burst neurons tested.

The effect of species-specific vocalization on the discharge of auditory cortical cells in the awake squirrel monkey. (Saimiri sciureus).

Action potentials of single auditory cortical neurons of the squirrel monkey were recorded in a chronic, unanesthetized preparation. The responsiveness of units was tested with various types of simple and complex acoustic stimuli in a free field situation. As simple auditory stimuli, bursts of pure tones, clicks, and white noise were utilized. Species-specific vocalizations served as complex, biologically significant stimuli. The data are based on 48 neurons which showed a discrete response to speciesspecific vocalizations. In 63% the response to calls could be predicted from the units' responses to simple stimuli. Thirty-seven percent of the neurons were classified as unpredictable with respect to their responsiveness to vocalizations. The response of most units was restricted to call stimuli which showed similarities in their frequency-time characteristics. About 7% of the 116 units responding to calls were classified as “selective responders” because they were not excited by any other stimulus tested. It was not possible to single out the acoustic features to which these units responded.

Electric reactions of the auditory cortex areas in bats to ultrasonic stimuli with various fill frequencies

The overall electric reactions and action potentials of single neurons in the auditory cortex were investigated for Vespertilionidae (Myotis oxygnathus) and Rhinolophidae (Rhinolophus ferrum equinum) narcotized with Hexenal. In the Vespertilionidae the greatest sensitivity to ultrasound is manifest at frequencies from 10 to 50 kHz, and in the Rhinolophidae for the ranges from 10 to 40 and from 82 to 84 kHz. The shapes of the response areas of single neurons in both types of bats are similar except for neurons discovered in Rhinolophidae that have three response areas with characteristic frequencies in the ranges 27–28, 40–42, and 80–84kHz. Narrow response areas with characteristic frequencies in the range from 70 to 90kHz appear on a considerable proportion of the neurons in the Rhinolophidae, but not the Vespertilionidae. Low thresholds are recorded to the stimulus cutoff in the range from 76 to 86 kHz.

Changes in action potentials of single phrenic motor neurons during activity.

Changes in action potentials of single phrenic motor neurons during activity.