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PubMed1985

Antidromic discharge property of meso-accumbens dopaminergic VTA neurons in rats.

Three groups of meso-accumbens (Acc) neurons in the ventral tegmental area were differentiated by their antidromic discharge property; dopaminergic type 1 (n = 10), non-dopaminergic type 2 (n = 2) and unclassified (n = 2) neurons. During repetitive activation at 10 Hz, the latency of the initial segment (IS) spike, which was often not followed by the somadendritic (SD) spike, was gradually prolonged in type 1, but not in type 2 and unclassified neurons. The latency prolongation of type 1 neurons was reduced to about a half of the normal in rats treated with kainic acid plus haloperidol, but only slightly when treated with kainic acid or picrotoxin. The rate of SD invasion tended to increase after all kinds of chemical treatment. Stimulation of the medial forebrain bundle in type 1 neurons gave responses comparable to Acc stimulation. It is suggested that the latency prolongation of IS spike is produced mainly by axonal mechanism. But additional somatic mechanisms such as dopaminergic self-inhibition and GABAergic and non-GABAergic inputs from the Acc would make some contribution, and at the same time produce frequent suppression of the antidromic SD spike.

Action Potentials↗

PubMedDate not supplied

CNV-like potentials on the cortical surface associated with conditioning in head-restrained rats.

Head-restrained rats were conditioned to perform a CNV task: to press a lever in response to an imperative auditory stimulus (S2) given 1.5 sec after a warning stimulus (S1) for a drop of jelly food. With an electrode on the surface of the forelimb cortex, (1) sharp wave complexes immediately after S1 and S2, and (2) a negative slow potential (SP) between S1 and S2, on which early and late components were discernible, were recorded in association with performance of this task. With the electrode at a depth of 2 mm in the same cortical area, the corresponding field potential showed a long-lasting positive shift in addition to the components of the surface potential. These monopolar recordings were obtained with respect to a common reference at the frontal sinus. The surface-minus-depth potential (the transcortical potential), consequently, showed a surface-negative tonic wave, confirming Pirch's report (1980). During extinction of this conditioning, the SP between S1 and S2 disappeared, while the sharp waves following S1 and S2 remained with little modification, suggesting that the sharp waves are a kind of evoked potential (EP) elicited by the stimuli. Recording from 5 surface electrodes set in an array over the left hemisphere contralateral to the used forelimb during development of the conditioning revealed not only a spatial distribution of the SP but also a transition of the potentials. As the conditioning progressed, the negativity of the early SP component tended to increase, while that of the late component tended to decrease and was confined to the sensorimotor cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗