PubMed · 6098927
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E Suematsu, Y Kanmura, T Itoh, H Kuriyama. 1984. [alpha-Adrenoceptor].. https://pubmed.ncbi.nlm.nih.gov/6098927/
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Neurons have the potential to form thousands of distinct neuronal nicotinic receptors from the eight alpha and three beta subunits that currently are known. In an effort to determine how much of this potential complexity is realized among individual neurons, we examined the nicotinic pharmacological and biophysical properties and receptor subunit mRNA expression patterns in individual neurons cultured from rat epicardial ganglia. Analysis of the whole-cell pharmacology of these neurons showed a diversity of responses to the agonists acetylcholine, nicotine, cytisine, and 1,1-dimethyl-4-phenylpiperazinium, suggesting that a heterogeneous population of nicotinic receptor classes, or subtypes, is expressed by individual neurons. Single-channel analysis demonstrated three distinct conductances (18, 24, and 31 pS), with patches from different neurons containing different combinations of these channel classes. We used single-cell RT-PCR to examine nicotinic acetylcholine receptor (nAChR) subunit mRNA expression by individual neurons. Although mRNAs encoding all eight neuronal nAChR subunits for which we probed (alpha 2-alpha 5, alpha 7, beta 2-beta 4) were present in multicellular cultures, we found that individual epicardial neurons express distinct subsets of these nAChR subunit mRNAs. These results suggest that individual epicardial neurons express distinct arrays of nAChR subunits and that these subunits may assemble into functional receptors with distinct and variable subunit composition. This variable receptor subunit expression provides an explanation for the diversity of pharmacological and single-channel responses we have observed in individual neurons.
The coherent representation of an object in the visual system has been suggested to be achieved by the synchronization in the gamma-band (30-70 Hz) of a distributed neuronal assembly. Here we measure variations of high-frequency activity on the human scalp. The experiment is designed to allow the comparison of two different perceptions of the same picture. In the first condition, an apparently meaningless picture that contained a hidden Dalmatian, a neutral stimulus, and a target stimulus (twirled blobs) are presented. After the subject has been trained to perceive the hidden dog and its mirror image, the second part of the recordings is performed (condition 2). The same neutral stimulus is presented, intermixed with the picture of the dog and its mirror image (target stimulus). Early (95 msec) phase-locked (or stimulus-locked) gamma-band oscillations do not vary with stimulus type but can be subdivided into an anterior component (38 Hz) and a posterior component (35 Hz). Nonphase-locked gamma-band oscillations appear with a latency jitter around 280 msec after stimulus onset and disappear in averaged data. They increase in amplitude in response to both target stimuli. They also globally increase in the second condition compared with the first one. It is suggested that this gamma-band energy increase reflects both bottom-up (binding of elementary features) and top-down (search for the hidden dog) activation of the same neural assembly coding for the Dalmatian. The relationships between high- and low-frequency components of the response are discussed, and a possible functional role of each component is suggested.
Swimming and the whole-body shortening reflex are two incompatible behaviors performed by the medicinal leech Hirudo medicinalis. We set out to examine the neuronal basis of the choice between these behaviors, taking advantage of the fact that the neuronal circuit underlying swimming is relatively well understood. The leech swim circuit is organized hierarchically and contains three interneuronal levels, including two upper levels of "command-like" neurons. We tested the responses of the swim circuit neurons to stimuli that produced shortening, using reduced preparations in which neurophysiological recording could be performed while behaviors were elicited. We found that the majority of the swim circuit neurons, including most of the command-like cells and all of the cells at the highest hierarchical level of the circuit, were excited by stimuli that produced shortening as well as by stimuli that produced swimming. Only a subset of neurons, at levels below the top, were inhibited during shortening; these included one of the command-like cells and an oscillator cell (an interneuron that is part of the central pattern generator for swimming). These results imply that the control of the choice between swimming and shortening is not exercised selectively at the higher levels of the swim circuit.