Effects of methadone on ornithine decarboxylase and cyclic nucleotide phosphohydrolase in neuronal and glial cell cultures

Developmental Brain Research

1991

SUMMARYTo determine whether exogenous opiate drugs with abuse liability directly modify neural growth, the present study investigated the effects of morphine on astrocyte proliferation and differentiation in primary cultures of murine glial cells. The results indicate that morphine decreases glial cell production in a dose-dependent, naloxone reversible manner. Most notably, gliogenesis virtually ceased in the presence of 10 −6 M morphine during the first week in culture, whereas 10 −8 M or 10 −10 M morphine caused an intermediate suppression of growth compared to control or 10 −6 M morphine treated cultures. Moreover, morphine-treatment inhibited [ 3 H]thymidine incorporation by glial fibrillary acidic protein (GFAP) immunoreactive, flat (type 1) astrocytes, suggesting that the decrease in glial cell production was due in part to an inhibition of astrocyte proliferation. Morphine also caused significant increases in both cytoplasmic area and process elaboration in flat (type 1) astrocytes indicating greater morphologic differentiation. In the above experiments, morphine-dependent alterations in astrocyte growth were antagonized by naloxone, indicating that morphine action was mediated by specific opioid receptors. These observations suggest that opiate drugs can directly modify neural growth by influencing two critical developmental events in astrocytes, i.e., inhibiting proliferation and inducing morphologic differentiation.

Section: Discussionmentioning

confidence: 99%

Morphine alters astrocyte growth in primary cultures of mouse glial cells: evidence for a direct effect of opiates on neural maturation

Stiene‐Martin

Gurwell

Developmental Brain Research

1991

“…During development, endogenous opioid neuropeptides typically act by inhibiting the growth of the nervous system (21,77,78). Opiate drugs such as morphine also affect neural development (9,12,14,16,17,42,52,54,58,62,66,70,74). Presumably opiate drugs disrupt the normal interactions between endogenous opioid peptides and their receptors.…”

Section: Introductionmentioning

confidence: 99%

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

Gurwell

Turbek

1994

Experimental Neurology

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.

“…There is considerable evidence that endogenous opioid systems (i.e., endogenous opioid peptides and opioid receptors) are involved in the regulation of neural growth in vivo (Vertes et al, 1982;Zagon and Mc-Laughlin, 1983;Hauser et al, 1987Hauser et al, , 1989Schmahl et al, 1989) and in vitro (Ruffin eta]., 1969;Vernadakis et al, 1982;Davila-Garcia and Azmitia, 1989;Hauser, 1989, 1990). By manipulating the interaction between endogenous opioids and their receptors, the number and rate of differentiation of neural cells can be modified in vivo with opioid peptides acting as negative trophic regulators of growth (Zagon and McLaughlin, 1983;Hauser et al, 1987.…”

Section: Introductionmentioning

confidence: 99%

“…The 5 opioid receptor is reported to have a pharmacological selectivity and specificity profile that is unique compared to p, 6, and K opioid receptors (Zagon et al, 1990a). p-Selective ligands have been reported to directly inhibit neurorlal (pyramidal cell) growth in the rat cerebral cortex in vivo (Hammer et al, 1989;Ricalde and Hammer, 1990); to depress ["]thymidine incorporation in rat brain in a naloxone reversible manner (Kornblum et a]., 1987a); to increase ornithine decarboxylase in glial cell cultures (Vernadakis et al, 1982); and to suppress [3H]thymidine incorporation by cerebellar neural cells in reaggregate cultures (Barg et al, 1990). Conversely, other studies report direct opioid-dependent modulation of growth by prototypic ligands that are selective for different opioid receptor types.…”

Section: Introductionmentioning

confidence: 99%

Glial growth is regulated by agonists selective for multiple opioid receptor types in vitro

Stiene‐Martin

J of Neuroscience Research

1991

To determine whether one or more opioid receptor types might be preferentially involved in gliogenesis, primary mixed glial cultures derived from mouse cerebra were continuously treated with varying concentrations of opioid agonists selective for mu (mu), i.e., DAGO ([D-Ala2, MePhe4, Gly(ol)5]enkephalin), delta (delta), i.e., DPDPE ([D-PEN2,D-PEN5]enkephalin), or kappa (kappa), i.e., U69,593, opioid receptor types. In addition, a group of cultures was treated with [Met5]-enkephalin, an agonist for delta opioid receptors as well as putative zeta (zeta) opioid receptors. Opioid-dependent changes in growth were assessed by examining alterations in (1) the number of cells in mixed glial cultures at 3, 6, and 8 days in vitro (DIV), (2) [3H]thymidine incorporation by glial fibrillary acidic protein (GFAP) immunoreactive, flat (type 1) astrocytes at 6 DIV, and (3) the area and form factor of GFAP-immunoreactive, flat (type 1) astrocytes. DPDPE at 10(-8) or 10(-10) M, as well as [Met5]-enkephalin at 10(-6), 10(-8), or 10(-10) M, significantly reduced the total number of glial cells in culture; but this effect was not observed with DAGO or U69,593 (both at 10(-6), 10(-8), or 10(-10) M). Equimolar concentrations (i.e., 10(-6) M) of [Met5]enkephalin or U69,593, but not DPDPE or DAGO, suppressed the rate of [3H]thymidine incorporation by GFAP-immunoreactive, flat (type 1) astrocytes. DAGO had no effect on growth, although in previous studies morphine was found to inhibit glial numbers and astrocyte DNA synthesis. [Met5]enkephalin (10(-6) M) was the only agonist to significantly influence astrocyte area. Collectively, these results indicate that delta (and perhaps mu) opioid receptor agonists reduce the total number of cells in mixed glial cultures; while [Met5]enkephalin-responsive (and perhaps kappa-responsive) opioid receptors mediate DNA synthesis in astrocytes. This implies that delta opioid receptors, as well as [Met5]enkephalin-sensitive, non-delta opioid receptors, mediate opioid-dependent regulation of astrocyte and astrocyte progenitor growth. These data support the concept that opioid-dependent changes in central nervous system growth are the result of endogenous opioid peptides acting through multiple opioid receptor types.