Evans RH. Pharmacology of amino acid receptors on vertebrate primary afferent nerve fibres.
GENERAL PHARMACOLOGY 1986;
17:5-11. [PMID:
2868969 DOI:
10.1016/0306-3623(86)90003-0]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Structure-activity of primary afferent depolarising action (PAD) mediated by gamma-aminobutyrate (GABA) analogues suggests a difference between subsynaptic receptors located at fibre terminations within the dorsal horn and axonal receptors which are distributed throughout non-synaptic regions. The interaction of the bicuculline-sensitive GABA receptor (GABA A) ionophore complex with barbiturates and benzodiazepines suggests that at least three binding sites are required to explain the independent GABA-mimetic, GABA-potentiating and picrotoxin-reversing effects of such agents. Difficulties with explanation of the depressant effects of baclofen on spinal transmission, in terms of the bicuculline-resistant GABA (GABA B) receptor hypothesis, are mentioned. Glutamate-induced PAD of low threshold afferents is mediated indirectly through release of potassium. However, such terminals possess receptors (possibly autoreceptors for L-glutamate), activated by (+)2-amino-4-phosphonobutyrate, which cause depression of transmitter release. Primary afferent C-fibres possess receptors which are selectively activated by kainate and which mediate picrotoxin-resistant PAD. Such receptors may be involved in the presynaptic conditioning of C-fibre transmitter release. The peripheral terminals of vestibular primary afferents, in amphibia, possess excitatory amino acid receptors which are probably activated by the transmitter released from hair cells.
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