This medical illustration consists of two sagittal-view anatomical diagrams of the human brain, serving as a Comparison Chart for neurotransmitter receptor co-expression. The diagrams specifically map the distribution of muscarinic and metabotropic glutamate receptors across the cortex, striatum, and hippocampus. The left schematic illustrates the co-expression of M4 receptors (light blue dots) and mGlu2 receptors (red dots), showing dense, uniform coverage in the cortex and striatum, with a relatively lower density in the hippocampus. The right schematic illustrates the co-expression of M4 receptors (light blue dots) and mGlu4 receptors (orange dots); here, the distribution is uniform in the cortex, but notably less dense in the striatum and hippocampus compared to the first diagram. These diagrams facilitate a visual comparison of neuroreceptor localization, which is critical for understanding the pathophysiology of schizophrenia and the development of targeted antipsychotic therapies. The content is designed for intermediate to advanced neuroscience education, focusing on neuroanatomy and synaptic pharmacology.

A molecular pharmacology diagram illustrating the conformational switch of the Cannabinoid Receptor 2 (CB2R) between active (left) and inactive (right) states. The visual depicts a G protein-coupled receptor (GPCR) model featuring alpha-helical transmembrane domains. The central mechanism shown is the 'toggle switch' involving the Trp258 residue within a 'secondary site/toggle pocket'. On the left, the agonist HU-308 binds to the primary site, leaving Trp258 in an upright active conformation. On the right, a modified ligand stabilizes the inactive state through a stereogenic phenyl group that engages in an edge-to-face pi-interaction with Trp258, effectively 'switching off' receptor signaling. Key molecular modifications to the ligand for therapeutic development are highlighted: 1) fluorophore conjugation for imaging, 2) stereogenic phenyl group for functional inactivation (e.g., inhibiting beta-arrestin association and ERK1/2 phosphorylation), 3) azide incorporation for improved affinity, and 4) a novel resorcinol moiety. The diagram highlights structural biology concepts in drug design, specifically targeting the active/inactive equilibrium of GPCRs for pain modulation research.

This medical illustration is an anatomical diagram showing a sagittal cross-section of a healthy human brain, used to visualize the distribution and expression intensity of M5 muscarinic receptors. The diagram employs a dotted pattern overlay where the density of purple dots serves as a semi-quantitative indicator of receptor concentration. Anatomical structures explicitly labeled with arrows include the cerebral cortex, striatum, and hippocampus. The cortex and hippocampus exhibit a moderate density of dots, representing significant receptor expression in these regions. In contrast, the striatum shows a lower density of dots, indicating a relatively lower concentration of M5 receptors. This schematic serves as an educational tool for neuroscience and neuropharmacology, illustrating specific regional receptor localization within the central nervous system and providing clinical context for potential drug targets in the treatment of cognitive or positive symptoms in neuropsychiatric disorders like schizophrenia.