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Effects of Noradrenaline on Frequency Tuning of Rat Auditory Cortex Neurons
Author(s) -
Manunta Yves,
Edeline JeanMarc
Publication year - 1997
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.1997.tb01433.x
Subject(s) - prazosin , auditory cortex , chemistry , medicine , endocrinology , bicuculline , antagonist , agonist , propranolol , population , inhibitory postsynaptic potential , norepinephrine , neuroscience , biology , receptor , dopamine , environmental health
The selectivity of rat auditory cortex neurons for pure tone frequency was studied during and after ionophoretic application (5–40 nA) of noradrenaline in urethane‐anaesthetized rats. The dominant effect induced by noradrenaline was a significant decrease in spontaneous (93/268 cells) and evoked activity (1331268 cells) which outlasted the application. In the whole population of cells (n = 268) the signal‐to‐noise ratio, computed using as the signal either the mean evoked response or the response at the best frequency, was unchanged during noradrenaline application. It was significantly increased only for cells showing significantly decreased spontaneous activity, and was significantly decreased for cells showing increased spontaneous activity. Frequency selectivity was significantly increased for the whole population during and after noradrenaline application. It was also significantly increased for cells showing significantly decreased evoked activity, and was significantly decreased for cells showing increased evoked activity. The noradrenaline‐induced inhibition was not blocked by propranolol (β antagonist); it was blocked by prazosin (α1 antagonist) and partly mimicked by phenylephrine (α1 agonist). GABA, which also inhibited spontaneous and evoked activity, slightly increased the signal‐to‐noise ratio and significant increased frequency selectivity. However, when noradrenaline was ejected in the presence of bicuculline at doses that were able to block GABAergic inhibition, the inhibitory effects of noradrenaline on spontaneous and evoked activity were still observed. The possible function of noradrenaline‐induced inhibitions in sensory cortices is briefly discussed.