title: Interdigitation of nitric oxide synthase-, tyrosine hydroxylase-, and serotonin-containing neurons in and around the laterodorsal and pedunculopontine tegmental nuclei of the guinea pig.
abstract: The topography of neurons containing nitric oxide synthase (NOS) and monoamines was investigated in the guinea pig mesopontine tegmentum. NOS-containing neurons were identified with NADPH-diaphorase (NADPH-d) histochemistry, and monoamine-containing neurons were identified with tyrosine hydroxylase (TH) and serotonin (5-HT) immunocytochemistry. The distribution of NADPH-d positive cells was centered on the laterodorsal tegmental (LDT) and pedunculopontine tegmental (PPT) nuclei. Diaphorase-containing cells had a mean soma diameter of 23.0 +/- 4.1 microns (n = 160) and were distributed inhomogeneously, with numerous cells found within densely packed clusters. A nearest-neighbor analysis revealed that these cells were closely spaced, with up to 20% within one cell diameter and more than 50% within two cell diameters of a neighboring NADPH-d cell. Within the LDT and PPT, NADPH-d positive cells were mixed with smaller, diaphorase-negative cells (diam: 12.8 +/- 3.3 microns; n = 182; P << 0.01). TH-containing cells were not organized into a compact LC as in rat and their distribution more closely resembled that observed in cat. On average, TH-containing cells (diam: 21.2 +/- 4.8 microns; n = 160) were smaller than NADPH-d cells (P < 0.01). 5-HT-containing cells were mainly located in the raphe nuclei, as in other species. 5-HT-containing cells (diam: 18.2 +/- 4.4 microns; n = 161) were smaller on average than both the NADPH-d (P < 0.01) and TH-containing cells (P < 0.01). An analysis of the overlap in soma distributions revealed that TH-containing cells were largely interdigitated with NADPH-d containing cells. As much as 78% of the area occupied by the NADPH-d cells of LDT was contained within the area occupied by TH cells. Substantial numbers of TH and 5-HT immunoreactive processes were seen in both LDT and PPT. Varicose 5-HT and TH-containing fibers, as well as thicker, possibly dendritic processes containing TH were often seen in close apposition to NADPH-d containing somata and proximal dendrites. These results support the hypothesis that NADPH-d cells of both the PPT and LDT receive input from TH and 5-HT cells. Moreover, the clustered substructure of LDT and PPT and the extensive overlap of NADPH-d and TH-containing somata raise the possibility that the membrane permeable messenger nitric oxide plays a role in modulating TH-containing somata and their processes as well as 5-HT-containing processes in the LDT and PPT.
authors.affiliation: Center for Neural Science, New York University, New York 10003, USA.
authors.forename: C S
authors.initials: CS
authors.lastname: Leonard
authors.forename: I
authors.initials: I
authors.lastname: Kerman
authors.forename: G
authors.initials: G
authors.lastname: Blaha
authors.forename: E
authors.initials: E
authors.lastname: Taveras
authors.forename: B
authors.initials: B
authors.lastname: Taylor
mesh_terms: D000818:Animals; D005260:Female; D006168:Guinea Pigs / Q000502:physiology*; D007150:Immunohistochemistry; D008125:Locus Coeruleus / Q000737:chemistry / Q000166:cytology / Q000201:enzymology; D008297:Male; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009474:Neurons / Q000737:chemistry / Q000201:enzymology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012154:Reticular Formation / Q000737:chemistry / Q000166:cytology / Q000201:enzymology*; D012701:Serotonin / Q000032:analysis*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
chemical_list: D012701:Serotonin; D019001:Nitric Oxide Synthase; D014446:Tyrosine 3-Monooxygenase; D009252:NADPH Dehydrogenase