Abstract
The retinohypothalamic tract (RHT) is a neural pathway through which photic time cues are delivered directly to the mammalian circadian pacemaker in the suprachiasmatic nucleus (SCN). Although the excitatory amino acid glutamate is the primary neurotransmitter in the RHT, other substances such as substance P (SPq also have been suggested to play a role. The present study tested the hypothesis that SP participates in retinohypothalamic transmission and selectively modulates either N-methyl-D-aspartate (NMDA) or non-NMDA receptor-mediated neurotransmission. The SP antagonist L-703,606 depressed the excitatory postsynaptic current (EPSC) evoked by optic nerve stimulation in SCN neurons in rat hypothalamic slices. The SP antagonist also had a similar depressive effect on the NMDA and non-NMDA receptor-mediated components of the EPSC. These results suggest that SP is an excitatory neuromodulator contributing to the expression of both the NMDA and non-NMDA receptor-mediated components of retinohypothalamic transmission.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
2-Amino-5-phosphonovalerate / pharmacology
-
Animals
-
Circadian Rhythm / physiology
-
Electrophysiology
-
Excitatory Amino Acid Antagonists / pharmacology
-
Excitatory Postsynaptic Potentials / drug effects
-
Excitatory Postsynaptic Potentials / physiology
-
Male
-
Neurotransmitter Agents / physiology
-
Quinoxalines / pharmacology
-
Quinuclidines / pharmacology
-
Rats
-
Rats, Sprague-Dawley
-
Receptors, N-Methyl-D-Aspartate / antagonists & inhibitors
-
Receptors, N-Methyl-D-Aspartate / physiology
-
Retina / chemistry
-
Retina / cytology*
-
Retina / physiology
-
Substance P / antagonists & inhibitors
-
Substance P / physiology*
-
Suprachiasmatic Nucleus / chemistry
-
Suprachiasmatic Nucleus / cytology*
-
Suprachiasmatic Nucleus / physiology
-
Synaptic Transmission / drug effects
-
Synaptic Transmission / physiology*
-
Visual Pathways
Substances
-
Excitatory Amino Acid Antagonists
-
Neurotransmitter Agents
-
Quinoxalines
-
Quinuclidines
-
Receptors, N-Methyl-D-Aspartate
-
L 703606
-
Substance P
-
FG 9041
-
2-Amino-5-phosphonovalerate