Multiple actions of 1S,3R-ACPD in modulating endogenous synaptic transmission to spinal respiratory motoneurons.
نویسندگان
چکیده
To determine physiological roles of metabotropic glutamate receptors (mGluRs) affecting breathing, we examined the effects of (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) on synaptic transmission and excitability of phrenic motoneurons (PMNs) in an in vitro neonatal rat brainstem/spinal cord preparation. The effects of 1S,3R-ACPD were multiple, including reduction of inspiratory-modulated synaptic currents and increase of neuronal excitability via an inward current (Iacpd) associated with a decrease of membrane conductance. The mechanism underlying synaptic depression was examined. We found that 1S,3R-ACPD reduced the frequency but not the amplitude of miniature excitatory postsynaptic currents. The current induced by exogenous AMPA was not significantly affected by 1S,3R-ACPD. These results suggest that 1S,3R-ACPD-induced reduction of inspiratory synaptic currents is mediated by presynaptic mGluRs. We also examined the ionic basis for Iacpd. We found that Iacpd had a reversal potential of approximately -100 mV, close to the estimated, EK+ (-95 mV). Elevating extracellular [K+] to 9 mM reduced the Iacpd reversal potential to -75 mV. The K+ channel blocker Ba2+ induced an inward current with a reversal potential at -93 mV associated with a decrease of membrane conductance, closely resembling the effect of 1S,3R-ACPD. Moreover, Ba2+, occluded 1S,3R-ACPD effects. In the presence of Ba2+, Iacpd and the 1S,3R-ACPD-induced decrease of membrane conductance were diminished. Our data indicate that the dominant component of Iacpd results from the blockade of a Ba(2+)-sensitive resting K+ conductance. We conclude that the activation of mGluRs affects the inspiratory-modulated activity of PMNs via distinct mechanisms at pre- and postsynaptic sites.
منابع مشابه
Regulation of intrinsic and synaptic properties of neonatal rat trigeminal motoneurons by metabotropic glutamate receptors.
We studied how metabotropic glutamate receptor (mGluR) activation modifies the synaptic and intrinsic membrane properties of neonatal rat trigeminal motoneurons using the broad-spectrum mGluR agonist (1S,3R)-1-amino-1,3-cyclopentane-dicarboxylic acid [(1S,3R)-ACPD], group I/II antagonist (+/-)-alpha-methyl-4-carboxy-phenylglycine (MCPG), and group III agonist L-2-amino-4-phosphonobutanoate (L-A...
متن کاملDistinct subtypes of metabotropic glutamate receptors mediate differential actions on excitability of spinal respiratory motoneurons.
Metabotropic glutamate receptors (mGluRs) modulate neuronal function by affecting excitability and altering synaptic transmission. We have shown that the mGluR agonist (1S,3R)-1-amino-1, 3-cyclopentanedicarboxylic acid (1S,3R-ACPD) has multiple actions on phrenic motoneurons (PMNs), including reduction of inspiratory-modulated synaptic currents and an increase of neuronal excitability. We hypot...
متن کاملActivation of group I metabotropic glutamate receptors induces long-term depression at sensory synapses in superficial spinal dorsal horn.
Low-frequency stimulation of primary afferent Adelta-fibers can induce long-term depression of synaptic transmission in rat superficial spinal dorsal horn. Here, we have identified another form of long-term depression in superficial spinal dorsal horn neurons that is induced by specific group I but not group II metabotropic glutamate receptor (mGluR) agonists. Synaptic strength between Adelta-f...
متن کاملPresynaptic depression of synaptic transmission mediated by activation of metabotropic glutamate receptors in rat neocortex.
Conventional intracellular recordings were obtained from layer II-III neurons in adult rat neocortical brain slices. Excitatory and inhibitory (I) postsynaptic potentials (PSPs) were evoked prior to and during bath application of agonists and antagonists of metabotropic glutamate receptors (mGluRs). In the presence of the selective mGluR agonist 1S,3R-1-aminocyclopentane-1,3- dicarboxylic acid ...
متن کاملThe effects of the metabotropic glutamate receptor agonist 1S,3R-ACPD on neurones in the rat primary somatosensory cortex in vivo.
The selective glutamate metabotropic receptor agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) was applied iontophoretically to cells in the rat primary somatosensory cortex (SI) in vivo. In contrast to other in vivo studies, distinct excitatory and depressant effects were observed. The excitatory responses could not be blocked by ionotropic antagonists, as evidence that t...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- The Journal of neuroscience : the official journal of the Society for Neuroscience
دوره 16 16 شماره
صفحات -
تاریخ انتشار 1996