Jacqueline F. McGinty

Translocation of zinc may contribute to seizure-induced death of neurons☆

Rats were subjected to seizures induced by kainic acid, and the resulting changes in CNS zinc staining were studied with the toluene sulfonamide quinoline fluorescence method. Seizures caused a loss of zinc staining from presynaptic boutons in many limbic and cerebrocortical regions. Simultaneously, the postsynaptic neurons that were degenerating (acidophilic) in those regions as a result of the seizure developed intense fluorescence for zinc. A possible role for zinc in the death of the postsynaptic neurons is suggested.

A Subset of β-Endorphin- or Dynorphin-Containing Neurons in the Medial Basal Hypothalamus Accumulates Estradiol

We used the combined steroid autoradiography-immunocytochemical method to determine whether estradiol- or dexamethasone-concentrating cells contain endogenous opioid peptides. Ovariectomized-adrenalectomized female rats were given highly radioactive doses of 3H-estradiol or 3H-dexamethasone, then sacrificed to demonstrate nuclear steroid binding. Autoradiograms were prepared, exposed for 2-12 months, photodeveloped, and fixed; immunocytochemistry was carried out on the same sections using antibodies to beta-endorphin or dynorphin A (1-17). In the medial basal hypothalamus, many estradiol- and some dexamethasone-concentrating neurons were found intermingled with beta-endorphin or dynorphin-immunoreactive neurons. Of the beta-endorphin-immunoreactive neurons in the medial basal hypothalamus, 4% concentrated estradiol in their nuclei. In addition, a subset of beta-endorphin-immunoreactive cells in the anterior pituitary concentrated estradiol in their nuclei. Although none of the beta-endorphin-immunoreactive neurons in the medial basal hypothalamus concentrated dexamethasone in their nuclei, many of the beta-endorphin-immunoreactive cells in the anterior pituitary did. Of the dynorphin-immunoreactive neurons in the medial basal hypothalamus, 10% concentrated estradiol in their nuclei. These data are consistent with the hypothesis of a genomic effect of estradiol on a particular subset of medial basal hypothalamic neurons that produce endogenous opioid peptides.

A single injection of amphetamine or methamphetamine induces dynamic alterations in c-fos,zif/268 and preprodynorphin messenger RNA expression in rat forebrain

In this study, the effects of a single dose of the indirect dopamine agonists amphetamine and methamphetamine on behavior and messenger RNA expression were evaluated. Expression of c-fos, a member of the leucine zipper family, zif/268 (NGFI-A, egr1 and Krox-24), a member of the zinc finger family, and the opioid peptide, preprodynorphin, was investigated in various regions of rat forebrain with quantitative in situ hybridization histochemistry 1, 2, 3, 6 or 30 h after injection. Behavioral observations indicated that a qualitatively different behavioral syndrome was induced following methamphetamine (15 mg/kg, i.p.) as compared with that observed after amphetamine (5 mg/kg, i.p.). Similarly, methamphetamine induced a different pattern of c-fos and zif/268 messenger RNA induction in sensory/motor cortex, dorsal striatum (caudatoputamen) and ventral striatum (nucleus accumbens) than did amphetamine. The increase in c-fos messenger RNA expression peaked at 1 h and returned to basal levels in all regions by 3 h. In contrast, the increase in zif/268 messenger RNA expression in the cortical regions was equally strong at 1 and 2 h, gradually returning to basal levels by 6 h after either drug. However, in the striatal regions, zif/268 messenger RNA levels peaked at 1 h and declined gradually to basal levels by 6 h. Interestingly, methamphetamine caused an actual suppression of zif/268 gene expression (> 50%) in both caudatoputamen and nucleus accumbens at 3 h. Preprodynorphin messenger RNA expression was increased in a patchy motif in the caudatoputamen and nucleus accumbens beginning at 2 h and returning to basal levels by 30 h after injection of either drug. This study, together with our recently published observation that preprodynorphin messenger RNA is induced in the caudate 3, 6 and 18 h after amphetamine or methamphetamine injection, provides a detailed dynamic description of the differential modulation of c-fos, zif/268 and preprodynorphin messenger RNA expression in the cerebral cortex and striatum by amphetamines over time. These data implicate immediate early gene and preprodynorphin gene expression in the differential response of medium spiny striatal neurons to methamphetamine and amphetamine.

Differential modulation of striatonigral dynorphin and enkephalin by dopamine receptor subtypes.

Previous studies indicate that dopaminergic transmission inhibits the biosynthesis of enkephalin and stimulates that of dynorphin in the striatonigral pathway of intact rat. The purpose of this study was to determine which dopamine (DA) receptor subtype(s) mediate the modulatory actions of DA. We measured striatal and nigral levels of enkephalin and dynorphin in: (1) intact rats repeatedly injected with D1 (SKF-38393, 5 mg/kg, i.p.) or D2 (LY-171555, 1 mg/kg, i.p.) agonists, alone or in combination, (2) 6-hydroxydopamine (6-OHDA)-lesioned rats repeatedly injected with the same D1 or D2 agonists, and (3) intact rats repeatedly injected with D1 (SCH-23390, 0.05 mg/kg, s.c.) or D2 (sulpiride, 100 mg/kg, s.c.) antagonists, given alone or in combination with the mixed D1/D2 agonist apomorphine (5 mg/kg, i.p.). Repeated injections of the D1 agonist to intact rats (twice daily for 7 days) produced a small but not statistically significant increase in striatal levels of dynorphin; similar treatment with the D2 agonist did not affect dynorphin levels at all. Combined treatments with D1 and D2 agonists did not potentiate the effect of the D1 agonist. 6-OHDA lesions of the nigrostriatal DA pathway alone decreased the level of dynorphin in both the striatum and substantia nigra. However, repeated D1 agonist, but not D2, injections not only reversed the decrease in dynorphin levels, but caused a significant increase above control levels. In intact rats, repeated injections of the D1 or D2 antagonist alone failed to alter the levels of dynorphin, but the D1 antagonist, not the D2 antagonist, attenuated the apomorphine-induced increase in striatal dynorphin.(ABSTRACT TRUNCATED AT 250 WORDS)

Repeated amphetamine administration induces a prolonged augmentation of phosphorylated cyclase response element-binding protein and Fos-related antigen immunoreactivity in rat striatum.

Semi-quantitative immunocytochemistry was used to investigate the levels of cyclase response element-binding protein, phosphorylated cyclase response element-binding protein, Fos and Fos-related antigen immunoreactivity in the striatum of rats after acute or repeated amphetamine administration. Rats were perfused 20 min (phosphorylated cyclase response element-binding protein) or 2 h (cyclase response element-binding protein, phosphorylated cyclase response element-binding protein, Fos, Fos-related antigen) after a single injection (5 mg/kg, i.p.) or five daily injections of amphetamine. The latency to onset of stereotypical behaviors was significantly reduced in rats exposed to repeated amphetamine as compared to acute amphetamine, indicating development of behavioral sensitization. Cyclase response element-binding protein immunoreactivity was not altered in the dorsal or ventral striatum following acute or repeated amphetamine. Phosphorylated cyclase response element-binding protein immunoreactivity was significantly induced 20 min, but not 2 h, following acute amphetamine, whereas a significant induction of phosphorylated cyclase response element-binding protein immunoreactivity was found 20 min and 2 h after repeated amphetamine in the dorsal striatum only. Fos immunoreactivity was significantly induced in the dorsal striatum following acute and repeated amphetamine. Fos immunoreactivity in the core of the nucleus accumbens was significantly increased following repeated amphetamine only. Acute amphetamine induced, and repeated amphetamine further augmented, Fos-related antigen immunoreactivity in the dorsal striatum, while not affecting Fos-related antigen immunoreactivity in the nucleus accumbens. These data demonstrate that repeated amphetamine administration results in a prolonged induction of phosphorylated cyclase response element-binding protein and Fos-related antigen immunoreactivity in the dorsal striatum, indicating that alterations in striatal gene expression associated with the development of behavioral sensitization may be mediated, in part, by these transcription factors.

D1 and D2 receptor regulation of preproenkephalin and preprodynorphin mRNA in rat striatum following acute injection of amphetamine or methamphetamine

Our previous work has demonstrated a dose‐dependent induction of striatal preprodynorphin (PPD) in response to a single injection of the psychostimulants amphetamine (AMPH) or methamphetamine (METH). In the present study, dose‐response effects of acute administration of these stimulants on preproenkephalin (PPE) mRNA expression in the rat striatum were investigated with quantitative in situ hybridization histochemistry 3 h after injection. Acute AMPH or METH at equimolar doses (3.75, 7.5, 15, and 30 μmol/kg) significantly increased PPE mRNA expression in dorsal (caudoputamen), but not ventral (nucleus accumbens), striatum in a dose‐dependent fashion. In addition, the role of D1 and D2 dopamine receptors in mediating AMPH‐ and METH‐stimulated PPE and PPD expression was also evaluated by using subtype‐specific antagonists. Pretreatment of rats with SCH 23390 (0.1 mg/kg, i.p.), a selective D1 receptor antagonist, completely blocked acute AMPH (21 μmol/kg, i.p.)‐ or METH (21 μmol/kg, i.p.)‐induced PPE as well as PPD mRNA expression in the caudoputamen. Pretreatment with eticlopride (0.5 mg/kg, i.p.), a selective D2 receptor antagonist, also blocked PPD induction by the two stimulants, but PPE induction was unaffected. Furthermore, SCH 23390 decreased, and eticlopride elevated, constitutive PPE mRNA levels in the caudoputamen. Neither antagonist had a significant effect on the basal level of PPE or PPD mRNA in the nucleus accumbens. These results demonstrate a clear dose‐related responsiveness of PPE gene expression in striatal neurons in response to acute administration of amphetamines, although the intensity of the response is far less than that for striatal PPD. Furthermore, both D1 and D2 subtypes of dopamine receptors mediate AMPH‐ and METH‐stimulated striatal PPD mRNA expression, whereas D1 receptor activation alone mediates amphetamine‐stimulated PPE mRNA expression in the rat striatum.

Acute amphetamine or methamphetamine alters opioid peptide mRNA expression in rat striatum.

The effects of a single dose of amphetamine or methamphetamine on opioid peptide gene expression in the dorsal and ventral striatum of rats were investigated by quantitative in situ hybridization 3, 6, or 18 h after injection. Although amphetamine-treated rats exhibited significantly different behaviors than those treated with methamphetamine, both drugs caused a patchy increase in preprodynorphin, but not preproenkephalin, mRNA in the caudate at all 3 time points. No changes were detected in the nucleus accumbens. These data indicate that prolonged elevation of preprodynorphin expression may alter the responsiveness of striatonigral neurons to subsequent amphetamine exposure.

Muscarinic receptors regulate striatal neuropeptide gene expression in normal and amphetamine-treated rats.

This study investigated the effects of pharmacological blockade or stimulation of muscarinic receptors on constitutive and amphetamine-stimulated preprodynorphin, substance P and pre-proenkephalin gene expression in rat striatum. Acute administration of the non-selective muscarinic antagonist, scopolamine (2.5, 5 and 10 mg/kg, s.c.), caused a dose-dependent increase in preprodynorphin and substance P, but not preproenkephalin, messenger RNA expression in the dorsal and ventral striatum as revealed by quantitative in situ hybridization. In contrast, acute injection of the non-selective muscarinic receptor agonist, oxotremorine (0.125, 0.25 and 0.5 mg/kg, s.c.), caused a dose-dependent increase in basal levels of preproenkephalin messenger RNA in the dorsal striatum, without causing a significant effect on constitutive striatal preprodynorphin and substance P expression. Pretreatment with scopolamine (2.5 mg/kg, s.c.) significantly augmented striatal induction of preprodynorphin and substance P messenger RNA induced by acute injection of amphetamine (1.25 and 2.5 mg/kg, i.p.), whereas scopolamine blocked amphetamine-stimulated striatal preproenkephalin expression. Pretreatment with oxotremorine (0.25 mg/kg, s.c.) significantly attenuated amphetamine (1.25 and 2.5 mg/kg, i.p.)-stimulated striatal preprodynorphin and, to a lesser degree, substance P messenger RNA expression. Oxotremorine tended to increase amphetamine-stimulated preproenkephalin messenger RNA expression, but the effect did not reach statistical significance. In addition, scopolamine increased spontaneous, and enhanced amphetamine-stimulated, behavioral activity, whereas oxotremorine attenuated amphetamine-stimulated behaviors. These data support the concept that cholinergic transmission, via interaction with muscarinic receptors, inhibits basal and D1 receptor-stimulated striatonigral dynorphin/substance P gene expression and facilitates striatopallidal enkephalin gene expression.

Scopolamine augments C-fos and zif/268 messenger rna expression induced by the full D1 dopamine receptor agonist SKF-82958 in the intact rat striatum

It is generally accepted that the widely used, partial dopamine D(1) receptor agonist, SKF-38393, does not induce immediate early gene expression in striatal projection neurons unless D(1) receptors are sensitized and uncoupled from D(2) receptors by 6-hydroxydopamine lesions or reserpine treatment. In contrast, this study demonstrates, using quantitative in situ hybridization, that the full D(1) receptor agonist, SKF-82958, induced robust expression of c-fos and zif/268 messenger RNAs in the intact rat striatum, especially in the entire shell and medial and ventral core areas of the nucleus accumbens and olfactory tubercle, and in the cerebral cortex, 45 min after one injection. The induction of the striatal immediate early genes is characterized by (i) induction in only medium-sized spiny neurons, (ii) dose-dependent induction, which correlates well with dose-dependent increases in motor activity, and (iii) blockade by the D(1) receptor antagonist, SCH-23390. The muscarinic cholinergic receptor antagonist, scopolamine, which itself did not alter striatal gene expression, profoundly augmented the behaviors and expression of the two immediate early genes in the ventral and dorsal striatum induced by 0.1, 0.5 and 2.0 mg/kg SKF-82958. However, scopolamine attenuated basal, and SKF-82958-stimulated, expression of c-fos and zif/268 messenger RNAs in the cortex. Scopolamine also enabled SKF-38393 to induce locomotor stimulation and c-fos and zif/268 messenger RNA expression in the normosensitive striatum of the rat when SKF-38393 alone caused no such changes. These data demonstrate an ability of SKF-82958 to induce immediate early gene messenger RNA expression in normosensitive dorsal and ventral striatum. Furthermore, intrinsic muscarinic receptor-mediated cholinergic transmission in the striatum may provide an activity-dependent inhibitory control on striatal D(1) receptor stimulation.

Amygdaloid kindling increases enkephalin-like immunoreactivity but decreases dynorphin-A-like immunoreactivity in rat hippocampus

The effects of amygdaloid kindling on the regional levels and distribution of enkephalin-like and dynorphin-A (DN)-like immunoreactivity (LI) were examined. One day after completion of kindling, radioimmunoassay revealed a 71% decrease in DN1-8-LI and a 43% increase in [Met5]-enkephalin-LI in the hippocampus. Immunostaining revealed a depletion of DN1-17-LI in the hippocampal mossy fiber pathway and an increase in [Leu5]-enkephalin-LI in the temporoammonic pathway. Four weeks after completion of kindling, the levels and immunostaining intensity of dynorphin and enkephalin in the hippocampus had returned to control values.