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Presynaptic and postsynaptic relations of mu-opioid receptors to gamma-aminobutyric acid-immunoreactive and medullary-projecting periaqueductal gray neurons.
J Comp Neurol. 2000 Apr 17; 419(4):532-42.JC

Abstract

The ventrolateral portion of the periaqueductal gray (PAG) is one brain region in which ligands of the mu-opioid receptor (MOR) produce analgesia. In the PAG, MOR ligands are thought to act primarily on inhibitory [e.g., gamma-aminobutyric acidergic (GABAergic)] neurons to disinhibit PAG output rather than directly on medullary-projecting PAG neurons. In this study, the ultrastructural localization of MOR immunolabeling was examined with respect to either GABAergic PAG neurons or PAG projection neurons that were labeled retrogradely from the rostral ventromedial medulla. Immunoreactivity for MOR and GABA often coexisted within dendrites. Dual-labeled profiles accounted for subpopulations of dendrites containing immunoreactivity for either MOR (65 of 145 dendrites; 45%) or GABA (65 of 183 dendrites; 35%). In addition, nearly half of PAG neuronal profiles (148 of 344 profiles) that were labeled retrogradely from the ventromedial medulla contained MOR immunoreactivity. MOR was distributed equally among retrogradely labeled neuronal profiles in the lateral and ventrolateral columns of the caudal PAG. With respect to the presynaptic distribution of MOR, approximately half of MOR-immunolabeled axon terminals (35 of 69 terminals) also contained GABA. Some MOR and GABA dual-immunolabeled axon terminals contacted unlabeled dendrites (11 of 35 terminals), whereas others contacted GABA-immunoreactive dendrites (15 of 35 terminals). Furthermore, axon terminals synapsing on medullary-projecting PAG neurons sometimes contained immunoreactivity for MOR. These data support the model that MOR ligands can act by inhibiting GABAergic neurons, but they also provide evidence that MOR ligands may act directly on PAG output neurons. In addition, MOR at presynaptic sites could affect both GABAergic neurons and output neurons. Thus, the disinhibitory model represents only partially the potential mechanisms by which MOR ligands can modulate output of the PAG.

Authors+Show Affiliations

Laboratory of Neurobiology and Behavior, The Rockefeller University, New York, New York 10021, USA. commonk@yahoo.comNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

10742719

Citation

Commons, K G., et al. "Presynaptic and Postsynaptic Relations of Mu-opioid Receptors to Gamma-aminobutyric Acid-immunoreactive and Medullary-projecting Periaqueductal Gray Neurons." The Journal of Comparative Neurology, vol. 419, no. 4, 2000, pp. 532-42.
Commons KG, Aicher SA, Kow LM, et al. Presynaptic and postsynaptic relations of mu-opioid receptors to gamma-aminobutyric acid-immunoreactive and medullary-projecting periaqueductal gray neurons. J Comp Neurol. 2000;419(4):532-42.
Commons, K. G., Aicher, S. A., Kow, L. M., & Pfaff, D. W. (2000). Presynaptic and postsynaptic relations of mu-opioid receptors to gamma-aminobutyric acid-immunoreactive and medullary-projecting periaqueductal gray neurons. The Journal of Comparative Neurology, 419(4), 532-42.
Commons KG, et al. Presynaptic and Postsynaptic Relations of Mu-opioid Receptors to Gamma-aminobutyric Acid-immunoreactive and Medullary-projecting Periaqueductal Gray Neurons. J Comp Neurol. 2000 Apr 17;419(4):532-42. PubMed PMID: 10742719.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Presynaptic and postsynaptic relations of mu-opioid receptors to gamma-aminobutyric acid-immunoreactive and medullary-projecting periaqueductal gray neurons. AU - Commons,K G, AU - Aicher,S A, AU - Kow,L M, AU - Pfaff,D W, PY - 2000/4/1/pubmed PY - 2000/5/16/medline PY - 2000/4/1/entrez SP - 532 EP - 42 JF - The Journal of comparative neurology JO - J. Comp. Neurol. VL - 419 IS - 4 N2 - The ventrolateral portion of the periaqueductal gray (PAG) is one brain region in which ligands of the mu-opioid receptor (MOR) produce analgesia. In the PAG, MOR ligands are thought to act primarily on inhibitory [e.g., gamma-aminobutyric acidergic (GABAergic)] neurons to disinhibit PAG output rather than directly on medullary-projecting PAG neurons. In this study, the ultrastructural localization of MOR immunolabeling was examined with respect to either GABAergic PAG neurons or PAG projection neurons that were labeled retrogradely from the rostral ventromedial medulla. Immunoreactivity for MOR and GABA often coexisted within dendrites. Dual-labeled profiles accounted for subpopulations of dendrites containing immunoreactivity for either MOR (65 of 145 dendrites; 45%) or GABA (65 of 183 dendrites; 35%). In addition, nearly half of PAG neuronal profiles (148 of 344 profiles) that were labeled retrogradely from the ventromedial medulla contained MOR immunoreactivity. MOR was distributed equally among retrogradely labeled neuronal profiles in the lateral and ventrolateral columns of the caudal PAG. With respect to the presynaptic distribution of MOR, approximately half of MOR-immunolabeled axon terminals (35 of 69 terminals) also contained GABA. Some MOR and GABA dual-immunolabeled axon terminals contacted unlabeled dendrites (11 of 35 terminals), whereas others contacted GABA-immunoreactive dendrites (15 of 35 terminals). Furthermore, axon terminals synapsing on medullary-projecting PAG neurons sometimes contained immunoreactivity for MOR. These data support the model that MOR ligands can act by inhibiting GABAergic neurons, but they also provide evidence that MOR ligands may act directly on PAG output neurons. In addition, MOR at presynaptic sites could affect both GABAergic neurons and output neurons. Thus, the disinhibitory model represents only partially the potential mechanisms by which MOR ligands can modulate output of the PAG. SN - 0021-9967 UR - https://www.unboundmedicine.com/medline/citation/10742719/Presynaptic_and_postsynaptic_relations_of_mu_opioid_receptors_to_gamma_aminobutyric_acid_immunoreactive_and_medullary_projecting_periaqueductal_gray_neurons_ L2 - https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0021-9967&date=2000&volume=419&issue=4&spage=532 DB - PRIME DP - Unbound Medicine ER -