Fig 1. CB₁ immunoreactivity.

Astrocytes (arrow) of the cerebral white matter of a six-month-old Beagle dog showing strong CB₁ receptor immunoreactivity (A) comparing to astrocytes of a four-week-old dog, which are only slightly positive (B). The ependymal cells (arrow) of a six-month-old dog lining the lateral ventricle strongly express CB₁ receptor (C, D). Similarly, ependymal cells lining the fourth ventricle and scattered neuroglial cells (E) are CB₁ receptor positive, as well as cells of the choroid plexus (F). IHC was performed using the avidin-biotin-peroxidase complex (ABC) method.