Differential innervation of individual melanotropes suggests a role for nonsynaptic inhibitory regulation of the developing and adult rat pituitary intermediate lobe

Synapse
B M ChronwallK A Gary

Abstract

Dopamine and GABA were detected in intermediate lobe axons around birth, and early axons were closely apposed to glial cells and processes, possibly using them for guidance. In the adult, axons containing colocalized dopamine and GABA were distributed in a distinct pattern within the lobe, with plexuses located dorsally and ventrally. Axons preferentially followed glial processes in interlobular septa, yet were also interspersed between melanotropes. Individual melanotropes were contacted by varying numbers of axon terminals, with some devoid of contacts. Boutons contained both small clear vesicles and large dense-cored vesicles; membrane specializations were not well-developed. From these findings we concluded that in addition to direct synaptic inhibition, dopamine and GABA could stimulate their receptors by mechanisms similar to "parasynaptic" [Schmitt (1984) Neuroscience, 13:991-1001] or "volume" [Agnati et al. (1995) Neuroscience, 69:711-726] transmission as proposed for the CNS. Humoral agents passing into the intermediate lobe from portal vessels, thus acting as classical hormones, further regulate the melanotropes. Moreover, approximately 50% of the axonal elements were closely apposed to glia, suggesting that glia coul...Continue Reading

References

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Oct 1, 1995·International Journal of Developmental Neuroscience : the Official Journal of the International Society for Developmental Neuroscience·K A GaryB M Chronwall
Oct 1, 1995·International Journal of Developmental Neuroscience : the Official Journal of the International Society for Developmental Neuroscience·S A SandsB M Chronwall
Apr 1, 1996·International Journal of Developmental Neuroscience : the Official Journal of the International Society for Developmental Neuroscience·B M ChronwallK A Gary
Jun 1, 1997·International Journal of Developmental Neuroscience : the Official Journal of the International Society for Developmental Neuroscience·S A Sands, B M Chronwall

Citations

Feb 17, 2000·Annals of the New York Academy of Sciences·B M ChronwallS A Sands
Sep 9, 2000·International Journal of Developmental Neuroscience : the Official Journal of the International Society for Developmental Neuroscience·B M ChronwallJ C Schwartz
Jun 2, 2005·International Journal of Developmental Neuroscience : the Official Journal of the International Society for Developmental Neuroscience·Maya Gadhvi PurisaiB M Chronwall

Related Concepts

Axon
Intropin
Gamma-Aminobutyric Acid, Zinc Salt (2:1)
Glial Fibrillary Acidic Protein
Glutamate Decarboxylase
Melanophores
Electron Microscopy
Parasympathetic Nervous System
Pituitary Stalk
Poly(A) Tail

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