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Acta Physiologica 2008; Volume 194, Supplement 665
The 59th National Congress of the Italian Physiological Society
9/17/2008-9/19/2008
Cagliari, Italy
NORADRENERGIC MODULATION OF N-METHYL-D-ASPARTATE-EVOKED NEURONAL RESPONSES MEDIATED BY 1-ADRENOCEPTOR IN VESTIBULAR SECONDARY NEURONS
Abstract number: P10
BARRESI1 M, GRASSO1 C, LI VOLSI1 G, LICATA1 F, SANTANGELO1 F
1Dept. Physiological Sciences, University of Catania, [email protected]
Aim:
The vestibular complex (VC) is a sensorimotor structure involved in the control of posture and eye movements. We had demonstrated that noradrenaline (NA) is able to modulate NMDA-elicited?excitations of VC neurons by?acting on? a2 and b-adrenoceptors. The aim of this study was to ascertain whether a1-adrenergic receptors are also involved in this modulation.
Methods:
Extracellular recordings of unitary neuronal activities were performed in the vestibular medial and superior nuclei of adult male Wistar rats anesthetized by an intraperitoneal injection of urethane (1,3 g/Kg). NMDA-evoked excitations were studied during microiontophoretic applications of either cirazoline (CIR), a NA agonist for a1-adrenergic receptors, or NA. The effects of prazosine (PRA), a NA antagonist for a1-adrenergic receptors were tested also.
Results:
A depression of the excitatory responses evoked by NMDA was observed in 7 of 9 units tested during long lasting (up to 88 min) application of CIR and in the 2 units studied during NA application. The effects induced by CIR and NA were antagonized by ejection of PRA. A test performed by using specific antibodies and the immunofluorescence staining technique verified a diffuse co-localization of NMDA and a1 adrenoreceptors throughout the VC.
Conclusion:
These results demonstrate that the depressive action exerted by NA on vestibular responsiveness to NMDA is partially mediated by a1-adrenergic receptors.
To cite this abstract, please use the following information:
Acta Physiologica 2008; Volume 194, Supplement 665 :P10