Action of substance P (neurokinin-1) receptor activation on rat neostriatal projection neurons

Substance P (SP) acts as a neurotransmitter in the neostriatum through the axon collaterals of spiny projection neurons. However, possible direct or indirect actions of SP on the neostriatal output neurons have not been described. Targets of SP terminals within the neostriatum include interneurons,...

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Published in:Synapse (New York, N.Y.) N.Y.), 1999-07, Vol.33 (1), p.26-35
Main Authors: Galarraga, Elvira, Hernández-López, Salvador, Tapia, Dagoberto, Reyes, Arturo, Bargas, José
Format: Article
Language:English
Subjects:
acetylcholine
Animals
Corpus Striatum - cytology
Corpus Striatum - drug effects
Corpus Striatum - physiology
dopamine
Electrophysiology
In Vitro Techniques
neostriatum
neuromodulation
Neurons - drug effects
Neurons - physiology
NK1 receptor
Peptide Fragments - pharmacology
Rats
Rats, Wistar
Receptors, Neurokinin-1 - agonists
Receptors, Neurokinin-1 - physiology
substance P
Substance P - analogs & derivatives
Substance P - pharmacology
Synaptic Transmission - physiology
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Summary:Substance P (SP) acts as a neurotransmitter in the neostriatum through the axon collaterals of spiny projection neurons. However, possible direct or indirect actions of SP on the neostriatal output neurons have not been described. Targets of SP terminals within the neostriatum include interneurons, spiny neurons, afferent fibers and boutons. SP induces the release of both dopamine (DA) and acetylcholine (ACh). Since some postsynaptic actions of both DA and ACh on spiny neurons are known, we asked if activation of neostriatal NK1‐class receptors is able to reproduce them. The SP NK1‐receptor agonist, GR73632 (1 μM), had both excitatory and inhibitory actions on virtually all spiny neurons tested at resting potential. The excitatory action was blocked by atropine and coursed with an increase in firing rate and input resistance (RN). The inhibitory action was blocked by haloperidol and coursed with a reduction in firing rate and RN. Therefore, the release of both DA and ACh induced by NK1‐receptor activation modulates indirectly the excitability of the projection neurons. SP facilitates the actions of these transmitters on the spiny neuron. A residual excitatory response to the NK1‐receptor agonist was observed in 30% of a sample of neurons tested in the presence of both haloperidol and atropine. The increase in RN that accompanied this response could be observed in the presence of 1 μM TTX or 100 μM Cd2+, suggesting a direct effect. Double labeling showed that only SP‐immunoreactive neurons were facilitated by NK1‐receptor activation in these conditions. Synapse 33:26–35, 1999. © 1999 Wiley‐Liss, Inc.
ISSN:0887-4476
1098-2396
DOI:10.1002/(SICI)1098-2396(199907)33:1<26::AID-SYN3>3.0.CO;2-4