Figure 1

DAGLα localization in the fetal cholinergic basal forebrain.

(a) Schema of 2-AG signaling during fetal development and in adulthood. Note the lack of both MGL in growth cones²⁸ and glial 2-AG inactivation during development, allowing 2-AG spread. (b,b₁) CB₁R mRNA in the medial septum (ms) at embryonic day (E)18.5 and postnatal day 1 (P1). (b₂,b₃) The lack of hybridization signal in sense control experiments (neocortex, P1) confirmed detection specificity. (c,c₁) A subpopulation of ChAT⁺ septal neurons was immunoreactive for CB₁Rs in neonates. (c₂–c₄) In the neonatal hippocampus, cholinergic afferents likely harbored CB₁Rs given the lack of physical signal separation for ChAT and CB₁R immunoreactivities. Solid and open arrowheads pinpoint the presence and lack of co-localization for select marker combinations, respectively. (c₅) Colocalization coefficients for cholinergic (ChAT⁺) and CB₁R⁺ boutons in the CA1 subfield of the neonatal hippocampus. Data on dual-labeled terminal subsets were expressed as the percentage of all cholinergic or CB₁R-containing synapses per field of view. (d–d₁) A subpopulation of p75^NTR+ neurons expressed DAGLα²⁸. p75^NTR+ neurons, assumed to acquire cholinergic phenotype⁴⁶, were generally situated proximal to DAGLα⁺ cells (arrowheads). (d₂–d₄) Representative images of cholinergic neurites coursing along DAGLα⁺ neurons and of adjacent p75^NTR+-DAGLα cell pairs in the medial septum. (d₅) Quantitative analysis of the portion of p75^NTR+ processes that apposed DAGLα⁺ perikarya (representative configuration: d₃,d₄) and of p75^NTR+ perikarya in the vicinity (<10 μm) of a DAGLα⁺ cell. (e,e₁) p75^NTR+ fibers (dashed lines) were found interspersed with DAGLα⁺ processes in the E18.5/P1 corpus callosum. Arrowheads indicate physical separation between fibers. (e₂) Distances between p75^NTR+ and DAGLα⁺ parallel fibers. Abbreviations: cc, corpus callosum; ml, midline; ls, lateral septum; pyr, pyramidal cells. Data were expressed as means ± s.e.m.; Scale bars = 100 μm (b₁), 20 μm (c), 10 μm (c₂,d₂–d₄), 5 μm (e₁), 2 μm (c₄).