The most frequently reported use of medical marijuana is for pain relief. However, its psychoactive component Δ9-tetrahydrocannabinol (THC) causes significant side effects. Cannabidiol (CBD) and β-caryophyllene (BCP), two other cannabis constituents, possess more benign side effect profiles and are also reported to reduce neuropathic and inflammatory pain. We evaluated the analgesic potential of CBD and BCP individually and in combination in a rat spinal cord injury (SCI) clip compression chronic pain model. Individually, both phytocannabinoids produced dose-dependent reduction in tactile and cold hypersensitivity in male and female rats with SCI. When co-administered at fixed ratios based on individual A50s, CBD and BCP produced enhanced dose-dependent reduction in allodynic responses with synergistic effects observed for cold hypersensitivity in both sexes and additive effects for tactile hypersensitivity in males. Antinociceptive effects of both individual and combined treatment were generally less robust in females than males. CBD:BCP co-administration also partially reduced morphine-seeking behavior in a conditioned place preference (CPP) test. Minimal cannabinoidergic side effects were observed with high doses of the combination. The antinociceptive effects of the CBD:BCP co-administration were not altered by either CB2 or μ-opioid receptor antagonist pretreatment but, were nearly completely blocked by CB1 antagonist AM251. Since neither CBD or BCP are thought to mediate antinociception via CB1 activity, these findings suggest a novel CB1 interactive mechanism between these two phytocannabinoids in the SCI pain state. Together, these findings suggest that CBD:BCP co-administration may provide a safe and effective treatment option for the management of chronic SCI pain.

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Adrenal medullary grafts generally exhibit poor viability when grafted into the striatum. Previous work in our laboratory demonstrated that chromaffin cells can survive well for up to 2 mo following grafting into the intact rat striatum after cells are isolated from the nonchromaffin supporting cells (fibroblasts and endothelial cells) of the adrenal medulla. The aim of the present study was to assess the long-term viability of isolated bovine chromaffin cells following grafting into the intact rat striatum. The viability of grafted bovine adrenal medullary chromaffin cells was compared in rats receiving either (a) perfused adrenal medulla; (b) isolated chromaffin cells; or (c) isolated chromaffin cells that were subsequently recombined with their nonchromaffin supporting cells. One year postimplantation, all graft types which included fibroblasts and endothelial cells were infiltrated with macrophages and demonstrated an abundance of cellular debris. No viable chromaffin cells were observed. In contrast, healthy tyrosine hydroxylase (TH) and dopamine beta hydroxylase (D beta H) immunoreactive chromaffin cells survived for 1 yr posttransplantation when grafted in isolation from the nonchromaffin constituents of the adrenal medulla. Good xenograft survival was achieved in this group despite the fact that these rats were only immunosuppressed for 1 mo postimplantation. Grafted cells demonstrated morphological characteristics of chromaffin cells in situ and these implants were not accompanied by macrophage infiltration. These data demonstrate that long-term survival of chromaffin cells can be achieved following intrastriatal implantation and the viability of grafted chromaffin cells is dependent upon the removal of the nonchromaffin supporting cells.

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Adrenal chromaffin cells have been utilized for several neural grafting applications, but limitations in allogeneic donor availability and dangers inherent in autografting limit the widespread use of this approach clinically. While xenogeneic donors offer promise as a source for cell transplantation in the central nervous system (CNS), immunologic responses to cellular components of the adrenal medulla have not been well characterized. To further study the host T cell xenogeneic response to chromaffin and passenger cells of the adrenal medulla, an in vitro lymphocyte proliferation assay was used. Lymphocyte proliferation was determined by mixing rat lymphocytes with potential stimulator cell subpopulations of the bovine adrenal medulla: isolated chromaffin cells, isolated endothelial cells, or passenger nonchromaffin cells, which include a mixture of fibroblasts, smooth muscle cells, and endothelial cells. As a positive control, bovine aortic endothelial cells were also used. 3[H]-thymidine incorporation, corresponding to lymphocyte proliferation, was measured. Results indicated that isolated bovine chromaffin cells produce only a mild, statistically insignificant stimulation of rat lymphocytes. In contrast, there was a significant response to passenger nonchromaffin cells of the adrenal medulla, especially endothelial cells. The inclusion of low levels of cyclosporin A in the cultures completely eliminated the mild proliferative response to isolated bovine chromaffin cells, while near toxic levels were necessary to abrogate the response to endothelial cells. Immunocytochemical analysis revealed that routine chromaffin cell isolation procedures result in the inclusion of a small percentage of endothelial cells, which may be responsible for the slight lymphocyte stimulation. The results of this study indicate that isolated chromaffin cells possess low immunogenicity, and suggest that passenger cells in the adrenal medulla, particularly endothelial cells, may be primarily responsible for progressive rejection in CNS grafts. Thus, removal of passenger nonchromaffin cells from xenogeneic donor tissues prior to transplantation may produce a more tolerated graft in rodent models of neural transplantation.