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403 Activation of locus coeruleus by stimulation of prefrontal cortex mediated by excitatory amino acid inputs
403
ACTIVATION OF LOCUS COERULEUS BY STIMULATION OF PREFRONTAL CORTEX MEDIATED BY EXCITATORY AMINO ACID INPUTS Dept. Physiology, Fukushima Medical College’, Dept. Psychiatry, School of Med., Allegheny University2 EIICHI JODO’, Gary Aston-Jones2 We examined the role of excitatory amino acids (EAAs) in activation of locus coeruleus (LC) neurons evoked by single pulse electrical stimulation of the medial prefrontal cortex (PFCm) in halothane anesthetized rats, by microinfusing antagonists of EAAs into LC while recording impulse activity of single LC neurons for PFCm stimulation: The results indicated that phasic activation of LC by PFCm stimulation is mediated by both NMDA- and non-NMDA-type EAA channels.
404
EFFECTS OF DOPAMINE ON THE RAT NEOSTRIATAL RONS IN VITRO. Lab for Neural Circuits, Bio-Mimetic Control Research Center, RIKEN
CHOLINERGIC
NEU-
Toshihiko Aosaki, Yasuo Kawaguchi We investigated the actions of DA and other dopaminergic agents on the striatal choline@ neurons in the slice preparation using whole-cell patch clamp technique. We found that almost all large aspiny neurons (25/26, 96.2%) showed depolarization or an inward shift in the holding potentials in response to bath-applied dopamine in a dose dependent manner either with an increase (19/25) or with a decrease or no change in membrane conductance (6/25). A Dl-like agonist, SKF38393, almost always excited them (29/30) with an increase (12/29), decrease (9/29) or no change (8/29) in membrane conductance. However, a Da-like agonist, quinpirole, exerted two different types of responses in them: an inward current (13/22) and outward current (g/22). Most cells that showed an inward current were associated with membrane conductance increase (11/13), whereas all cells that showed an outward current (9/9) exhibited an increase in membrane conductance.
405
Low-frequency blockade Dept. Pharmacol., Jikei Univ.
vagal input prevents central inspiratory
off-switch under NMDA-receptor
Kazuo Takano, Fusao Kato It is known that a stimulation of vagal tierents induces an inspiratory (I) off-switch. This phenomenon is considered as a neural basis of the Hering-Breuer’s “inflation reflex”. However, the neural correlates underlying the “deflation reflex”, originally described as a promotion of inspiration under lung deflation, are still unclear. To study this mechanism, we stimulated the vagal afferent at a lower frequency than to induce I off-switch in rabbits anesthetized and artificially ventilated. A sustained vagal stimulation at a low frequency (540Hz) shortened slightly the expiratory phase. Under blockade of NMDA receptors with either of dizocilpine, ketamine or APV, the same vagal stimulation prevented the spontaneous I termination and maintained I phase. This effect was attenuated by NBQX. It is interpreted that the NMDA-receptor blockade unmasked an I-maintaining contribution of vagal afferents whose optimal response is obtained at -2OHz and presumably mediated by AMPA receptors.
ACTIVATION OF LOCUS COERULEUS BY STIMULATION OF PREFRONTAL CORTEX MEDIATED BY EXCITATORY AMINO ACID INPUTS Dept. Physiology, Fukushima Medical College’, Dept. Psychiatry, School of Med., Allegheny University2 EIICHI JODO’, Gary Aston-Jones2 We examined the role of excitatory amino acids (EAAs) in activation of locus coeruleus (LC) neurons evoked by single pulse electrical stimulation of the medial prefrontal cortex (PFCm) in halothane anesthetized rats, by microinfusing antagonists of EAAs into LC while recording impulse activity of single LC neurons for PFCm stimulation: The results indicated that phasic activation of LC by PFCm stimulation is mediated by both NMDA- and non-NMDA-type EAA channels.
404
EFFECTS OF DOPAMINE ON THE RAT NEOSTRIATAL RONS IN VITRO. Lab for Neural Circuits, Bio-Mimetic Control Research Center, RIKEN
CHOLINERGIC
NEU-
Toshihiko Aosaki, Yasuo Kawaguchi We investigated the actions of DA and other dopaminergic agents on the striatal choline@ neurons in the slice preparation using whole-cell patch clamp technique. We found that almost all large aspiny neurons (25/26, 96.2%) showed depolarization or an inward shift in the holding potentials in response to bath-applied dopamine in a dose dependent manner either with an increase (19/25) or with a decrease or no change in membrane conductance (6/25). A Dl-like agonist, SKF38393, almost always excited them (29/30) with an increase (12/29), decrease (9/29) or no change (8/29) in membrane conductance. However, a Da-like agonist, quinpirole, exerted two different types of responses in them: an inward current (13/22) and outward current (g/22). Most cells that showed an inward current were associated with membrane conductance increase (11/13), whereas all cells that showed an outward current (9/9) exhibited an increase in membrane conductance.
405
Low-frequency blockade Dept. Pharmacol., Jikei Univ.
vagal input prevents central inspiratory
off-switch under NMDA-receptor
Kazuo Takano, Fusao Kato It is known that a stimulation of vagal tierents induces an inspiratory (I) off-switch. This phenomenon is considered as a neural basis of the Hering-Breuer’s “inflation reflex”. However, the neural correlates underlying the “deflation reflex”, originally described as a promotion of inspiration under lung deflation, are still unclear. To study this mechanism, we stimulated the vagal afferent at a lower frequency than to induce I off-switch in rabbits anesthetized and artificially ventilated. A sustained vagal stimulation at a low frequency (540Hz) shortened slightly the expiratory phase. Under blockade of NMDA receptors with either of dizocilpine, ketamine or APV, the same vagal stimulation prevented the spontaneous I termination and maintained I phase. This effect was attenuated by NBQX. It is interpreted that the NMDA-receptor blockade unmasked an I-maintaining contribution of vagal afferents whose optimal response is obtained at -2OHz and presumably mediated by AMPA receptors.