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GABA-immunoreactive neurons and terminals in the cat periaqueductal gray matter: a light and electron microscopic study.
J Neurocytol. 2005 Dec; 34(6):471-87.JN

Abstract

Immunocytochemical and electron microscopic methods were used to study the GABAergic innervation in adult cat periaqueductal gray matter (PAG). A mouse monoclonal antibody against gamma -aminobutyric acid (GABA) was used to visualize the inhibitory neuronal system of PAG. At light microscopy, GABA-immunopositive (GABA(IP)) neurons formed two longitudinally oriented columns in the dorsolateral and ventrolateral PAG that accounted for 36% of the neuronal population of both PAG columns; their perikaryal cross-sectional area was smaller than that of unlabeled (UNL) neurons found in the same PAG subdivisions. At electron microscopic level, patches of GABA immunoreactivity were readily detected in neuronal cell bodies, proximal and distal dendrites, axons and axon terminals. Approximately 35-36% of all terminals were GABA(IP); they established symmetric synapses with dendrites (84.72% of the sample in the dorsolateral PAG and 86.09% of the sample in the ventrolateral PAG) or with cell bodies (7-10% of the sample). Moreover, 49.15% of GABA(IP) axon terminals in the dorsolateral and 52.16% in the ventrolateral PAG established symmetric synapses with GABA(IP) dendrites. Immunopositive axon terminals and unlabeled terminals were also involved in the formation of a complex synaptic arrangment, i.e. clusters of synaptic terminals in close contact between them that were often observed in the PAG neuropil. Moreover, a fair number of axo-axonic synapses between GABA(IP) and/or UNL axon terminals were present in both PAG subdivisions. Several dendro-dendritic synapses between labeled and unlabeled dendrites were also observed in both PAG subdivisions. These results suggest that in the cat PAG there exist at least two classes of GABArgic neurons. The first class could exert a tonic control on PAG projecting neurons, the second could act on those GABAergic neurons that in turn keep PAG projecting neurons under tonic inhibition. The functional implications of this type of GABAergic synapse organization are discussed in relation to the dishinibitory processes that take place in the PAG.

Authors+Show Affiliations

Department of Neurosciences, Section of Human Physiology, Marche Polytechnic University, Via Tronto 10/A-Torrette di Ancona, I-60020, Ancona, Italy p.barbaresi@univpm.it

Pub Type(s)

Journal Article

Language

eng

PubMed ID

16902767

Citation

Barbaresi, Paolo. "GABA-immunoreactive Neurons and Terminals in the Cat Periaqueductal Gray Matter: a Light and Electron Microscopic Study." Journal of Neurocytology, vol. 34, no. 6, 2005, pp. 471-87.
Barbaresi P. GABA-immunoreactive neurons and terminals in the cat periaqueductal gray matter: a light and electron microscopic study. J Neurocytol. 2005;34(6):471-87.
Barbaresi, P. (2005). GABA-immunoreactive neurons and terminals in the cat periaqueductal gray matter: a light and electron microscopic study. Journal of Neurocytology, 34(6), 471-87.
Barbaresi P. GABA-immunoreactive Neurons and Terminals in the Cat Periaqueductal Gray Matter: a Light and Electron Microscopic Study. J Neurocytol. 2005;34(6):471-87. PubMed PMID: 16902767.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - GABA-immunoreactive neurons and terminals in the cat periaqueductal gray matter: a light and electron microscopic study. A1 - Barbaresi,Paolo, Y1 - 2006/08/10/ PY - 2005/06/29/received PY - 2006/06/08/accepted PY - 2006/02/13/revised PY - 2006/8/12/pubmed PY - 2006/11/4/medline PY - 2006/8/12/entrez SP - 471 EP - 87 JF - Journal of neurocytology JO - J. Neurocytol. VL - 34 IS - 6 N2 - Immunocytochemical and electron microscopic methods were used to study the GABAergic innervation in adult cat periaqueductal gray matter (PAG). A mouse monoclonal antibody against gamma -aminobutyric acid (GABA) was used to visualize the inhibitory neuronal system of PAG. At light microscopy, GABA-immunopositive (GABA(IP)) neurons formed two longitudinally oriented columns in the dorsolateral and ventrolateral PAG that accounted for 36% of the neuronal population of both PAG columns; their perikaryal cross-sectional area was smaller than that of unlabeled (UNL) neurons found in the same PAG subdivisions. At electron microscopic level, patches of GABA immunoreactivity were readily detected in neuronal cell bodies, proximal and distal dendrites, axons and axon terminals. Approximately 35-36% of all terminals were GABA(IP); they established symmetric synapses with dendrites (84.72% of the sample in the dorsolateral PAG and 86.09% of the sample in the ventrolateral PAG) or with cell bodies (7-10% of the sample). Moreover, 49.15% of GABA(IP) axon terminals in the dorsolateral and 52.16% in the ventrolateral PAG established symmetric synapses with GABA(IP) dendrites. Immunopositive axon terminals and unlabeled terminals were also involved in the formation of a complex synaptic arrangment, i.e. clusters of synaptic terminals in close contact between them that were often observed in the PAG neuropil. Moreover, a fair number of axo-axonic synapses between GABA(IP) and/or UNL axon terminals were present in both PAG subdivisions. Several dendro-dendritic synapses between labeled and unlabeled dendrites were also observed in both PAG subdivisions. These results suggest that in the cat PAG there exist at least two classes of GABArgic neurons. The first class could exert a tonic control on PAG projecting neurons, the second could act on those GABAergic neurons that in turn keep PAG projecting neurons under tonic inhibition. The functional implications of this type of GABAergic synapse organization are discussed in relation to the dishinibitory processes that take place in the PAG. SN - 0300-4864 UR - https://www.unboundmedicine.com/medline/citation/16902767/GABA_immunoreactive_neurons_and_terminals_in_the_cat_periaqueductal_gray_matter:_a_light_and_electron_microscopic_study_ L2 - https://doi.org/10.1007/s11068-006-9440-7 DB - PRIME DP - Unbound Medicine ER -