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Age‐related differences in NMDA/metabotropic glutamate receptor binding in rat substantia nigra
Author(s) -
Hedberg Thomas G.,
Velı́šková Jana,
Sperber Ellen F.,
Nunes Magda L.,
Moshé Solomon L.
Publication year - 2003
Publication title -
international journal of developmental neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.761
H-Index - 88
eISSN - 1873-474X
pISSN - 0736-5748
DOI - 10.1016/s0736-5748(02)00125-9
Subject(s) - pars compacta , pars reticulata , substantia nigra , ampa receptor , metabotropic glutamate receptor , glutamate receptor , biology , nmda receptor , neuroscience , medicine , endocrinology , chemistry , receptor , biochemistry , dopamine , dopaminergic
Both N ‐methyl‐ d ‐aspartate (NMDA) and quisqualate/AMPA‐insensitive metabotropic glutamate (mGlu) receptors mediate glutamate neurotransmission in substantia nigra (SN). In this work, NMDA and mGlu receptor sites in substantia nigra pars compacta (SNC) and pars reticulata were autoradiographically mapped in rat brains using specific binding of (+) 3 H‐MK801 or 3 H‐glutamate, with saturating concentrations of NMDA, AMPA and quisqualate. In brains of both adult and postnatal day 15 (PN15) male rats, prepared at subjective mid‐day of a 12 h light/12 h dark (12 h L/12 h D) cycle, specific binding at NMDA and mGlu sites in substantia nigra was pronounced when compared with control binding. The (+) 3 H‐MK801 binding in adults was spatially heterogeneous. Overall binding density in pars compacta was higher relative to binding density in pars reticulata with a mean percent change ( ( Δ x ¯ % ) ) of 32%. Within the pars reticulata but not pars compacta, there were rostro‐caudal differences with considerably denser binding in the posterior compared with the anterior pars reticulata ( ( Δ x ¯ % = 108 % ) ). PN15 rats showed a less pronounced heterogeneity in pars compacta versus pars reticulata binding, ( ( Δ x ¯ % = 27 % ) ), and less rostro‐caudal differentiation in (+) 3 H‐MK801 binding density throughout pars reticulata ( ( Δ x ¯ % = 46 % ) ). 3 H‐glutamate binding in both adult and PN15 rats was less dense overall than (+) 3 H‐MK801 binding. In adults, there was no difference in binding density between pars compacta and pars reticulata ( ( Δ x ¯ % = 0.4 % ) ), but there were marked heterogeneities when binding was compared between anterior versus posterior pars compacta ( ( Δ x ¯ % = 29 % ) ), and anterior versus posterior pars reticulata ( ( Δ x ¯ % = 25 % ) ). This rostro‐caudal heterogeneity in 3 H‐glutamate binding density was also present in PN15 pars compacta ( ( Δ x ¯ % = 45 % ) ) but not in pars reticulata. Our findings mirror similar anterior/posterior heterogeneities in the GABAergic system in adult and PN15 male rats and may reflect a developmental change in both the structure and anticonvulsant/proconvulsant properties of substantia nigra pars reticulata (SNR) with age.