Checkpoint 1: ECS Anatomy

1In companion animals, Cannabinoid Receptor Type 1 (CB1) is predominantly concentrated in which anatomical structure, accounting for the neuro-pharmacological sensitivity observed during agonist binding?

A. Presynaptic terminals within the central nervous system, including the cerebral cortex, basal ganglia, and cerebellum ✓ B. Surface membranes of circulating B-lymphocytes and splenic macrophages within the reticuloendothelial system C. Bronchial smooth muscle cells and pulmonary microvascular endothelial parenchyma D. Distal convoluted tubules and juxtaglomerular cells within the renal cortex

Explanation: CB1 receptors are G-protein coupled receptors predominantly localized presynaptically within the central nervous system (CNS), particularly in the cerebral cortex, basal ganglia, and cerebellum. Their activation modulates neurotransmitter release (e.g., glutamate and GABA via retrograde signaling). In contrast, CB2 receptors are primarily localized in immune and peripheral tissues.

2Which of the following statements regarding the anatomical distribution and tissue expression of Cannabinoid Receptor Type 2 (CB2) in veterinary species are correct? (Select all that apply)

Select all that apply

A. CB2 receptors are predominantly expressed on peripheral immune cells, including leukocytes, lymph nodes, and splenic tissue. ✓ B. CB2 receptor activation in the central nervous system occurs mainly on activated microglial cells during neuroinflammatory states. ✓ C. CB2 receptors are densely localized on presynaptic motor neurons in the cerebral cortex, directly mediating classical psychotropic toxicosis signs. D. CB2 expression is dynamically upregulated in inflamed peripheral tissues, such as osteoarthritic synovium and painful cutaneous lesions. ✓

Explanation: CB2 receptors are primarily immune-modulatory receptors expressed peripherally on leukocytes, spleen, and lymphatic structures. During tissue trauma or inflammation (such as canine osteoarthritis), peripheral CB2 expression is dynamically upregulated. Within the CNS, baseline neuronal expression of CB2 is minimal; however, it is expressed on non-neuronal cells like activated microglia and astrocytes during neuroinflammation. Classical psychotropic effects and static ataxia are mediated by neuronal CB1 receptors, not CB2.

Clinical Disclaimer

This course is for veterinary continuing education. It does not constitute veterinary advice or a recommendation to prescribe any specific product. No therapeutic claims are made for unapproved products.