Morphine Inhibits Purkinje Cell Survival and Dendritic Differentiation in Organotypic Cultures of the Mouse Cerebellum

Abstract

The effects of morphine on the morphogenesis and survival of calbindin-D 28k immunoreactive Purkinje cells was studied in organotypic explant cultures isolated from 1-or 7-day-old mouse cerebella. To reduce experimental variability, bilaterally matched pairs of organotypic cultures were used to compare the effects of opiate drug treatment. One explant within each pair was untreated, while the remaining explant was continuously treated for 7 to 10 days with morphine, morphine plus naloxone, or naloxone alone. In explants derived from 1-day-old mice, morphine treatment significantly reduced Purkinje cell dendritic length compared to symmetrically-matched untreated control explants. The concentration of morphine estimated to cause a half-maximal reduction (EC 50 ) in dendritic length was 4.9 × 10 −8 M. At higher concentrations (EC 50 = 3.6 × 10 −6 M), morphine also significantly decreased the number of Purkinje cells in explants from 1-day-old mice compared to untreated explants. Electron microscopy identified increased numbers of degenerating Purkinje cells in explants derived from 1-day-old mice. This showed that high concentrations (10 −5 M) of morphine reduced Purkinje cell numbers by decreasing their rate of survival. In explants derived from 7-day-old mice, morphine (10 −5 M) neither affected Purkinje cell dendritic length nor cell numbers compared to symmetrically-matched untreated (control) explants. Collectively, these findings suggest that morphine per se, through a direct action on the cerebellum, can affect Purkinje cell differentiation and survival. The results additionally suggest there is a critical period during development when Purkinje cells are especially vulnerable to the effects of morphine.

Histological and histomorphometric studies on the cerebellar cortex and silver stained nucleolus organizer regions of Purkinje neurons in chronic morphine-treated rats

“…Morphine sulfate administration can also cause neurotoxic effects on the cerebellar and cerebral cortex by reducing both cortical thickness and the number of neurons in the developing fetal central nervous system (SADRAIE et al, 2008), also significantly reducing the Purkinje cell count (BEKHEET et al, 2010). Purkinje cells in morphine treated animals might be lost by apoptosis and/or necrosis (HAUSER et al, 1994). The morphometric results of the present study showed that morphine-treatment significantly decreased the Purkinje cell count in a unit length of the ganglionic layer in both genders in a similar manner.…”

“…In a later study, HAUSER et al (1994) showed that morphine significantly decreased Purkinje cell survival at higher concentrations, by decreasing the cells' survival. the researchers concluded that morphine can affect Purkinje cell differentiation and survival, and there is a critical period during development when Purkinje cells are especially vulnerable to the effects of morphine.…”

“…HAUSER (1992) found a significant reduction in DNA synthesis by external granular layer (eGL) neuroblasts in a 10-day-old rat cerebellum in the presence of 1 µM morphine, and concluded that morphine could directly regulate the growth of the developing cerebellum by inhibiting neuroblast proliferation within the eGL. In a later study, HAUSER et al (1994) showed that morphine significantly decreased Purkinje cell survival at higher concentrations, by decreasing the cells' survival. the researchers concluded that morphine can affect Purkinje cell differentiation and survival, and there is a critical period during development when Purkinje cells are especially vulnerable to the effects of morphine.…”

Dynorphin A (1–13) Neurotoxicity in Vitro: Opioid and Non-Opioid Mechanisms in Mouse Spinal Cord Neurons

“…For example, some of the diversity of opioid actions in part results from an apparent promiscuity in coupling between individual opioid receptor types and particular G-protein coupled-intracellular effector pathways (16,34,37,90). In the cerebellum, rather than being neuroprotective, high concentrations of morphine are neurotoxic to Purkinje cells through an action at μ opioid receptors (33). Lastly, any potentially neuroprotective effects of κ receptor activation appear to be offset by the more deleterious systemic pathophysiological actions of opioids.…”

Interactive Comorbidity between Opioid Drug Abuse and HIV-1 Tat

“…Dendritic pruning and selective postsynaptic damage have been reported with HIV-1 or SIV infections in the CNS. 46 -48 In addition to viral and cellular toxins associated with HIV, 2,49,50 endogenous opioids, 32,51 as well as opioid drugs such as morphine and methadone, [52][53][54] can also shrink dendrites and reduce the density of their spines. 43,55 Opioid drugs also affect the plasticity of adult neurons.…”