Elsevier

Neuroscience Letters

Volume 93, Issues 2–3, 11 November 1988, Pages 158-163
Neuroscience Letters

Autoradiographic and electrophysiological evidence for excitatory amino acid transmission in the periaqueductal gray projection to nucleus raphe magnus in the rat

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Abstract

Selective retrograde labelling was used as an autoradiographic method to identify possible excitatory amino acid afferents to nucleus raphe magnus (NRM). Injections of 25–50 nl 10−2 or 10−3 M d-[3H]aspartate into the NRM resulted in prominent labelling of cells in ventrolateral mesencephalic periaqueductal gray (PAG). Electrophysiologically, stimulation in ventrolateral PAG excited cells in NRM with a latency of 2–12 ms. With many cells, microelectrophoretic application of the excitatory amino acid antagonists, kynurenate and γ-d-glutamyl-glycine, resulted in a reversible reduction of the PAG-evoked response. Selective antagonists of N-methyl-d-aspartate (NMDA) were less effective. It is suggested that neurones in the ventrolateral PAG projecting to NRM utilize an excitatory amino acid or structurally related compound as a transmitter, and that this transmitter acts on receptors of the non-NMDA type.

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