Enhancement of opioid cataleptic response by cortical frontal deafferentation or intrastriatal injection of NMDA-receptor antagonists

Intrastriatal injection of a muscarinic receptor agonist and antagonist regulates striatal neuropeptide mRNA expression in normal and amphetamine-treated rats

Systemic administration of the muscarinic receptor antagonist, scopolamine, augments, whereas the muscarinic receptor agonist, oxotremorine, attenuates behaviors (locomotion and stereotypies) and preprodynorphin (PPD) and substance P (SP) gene expression in striatonigral neurons induced by the indirect dopamine receptor agonist, amphetamine (AMPH). In contrast, systemic scopolamine blocks, whereas oxotremorine augments, AMPH-stimulated preproenkephalin (PPE) gene expression in striatopallidal neurons. This study investigated the site of action of these effects by administering scopolamine and oxotremorine directly into the striatum and assessing the expression of neuropeptide mRNAs with quantitative in situ hybridization. Unilateral injection of scopolamine into the dorsal striatum augmented, and oxotremorine attenuated, AMPH (2.5 mg/kg, i.p.)-stimulated behaviors. Intrastriatal scopolamine at a concentration of 62 mM, but not 6.2 mM, increased basal levels of PPD and SP mRNAs in the dorsal striatum. In addition, both 6.2 and 62 mM scopolamine significantly augmented AMPH-stimulated PPD and SP mRNA levels. Intrastriatal infusion of 1.6 or 8.1 mM oxotremorine did not alter basal levels of striatal PPD and SP mRNAs. However, both concentrations of oxotremorine completely blocked AMPH-stimulated SP mRNA and oxotremorine at 8.1 mM blocked AMPH-stimulated PPD mRNA. In contrast, PPE induction by AMPH was blocked by 62, but not 6.2, mM scopolamine. Both concentrations of oxotremorine tended to augment basal and AMPH-stimulated PPE mRNA in the dorsal striatum but the trend was not significant. These data demonstrate an inhibition of striatonigral, and facilitation of striatopallidal, gene expression through activation of local striatal muscarinic receptors, which is consistent with the changes seen after systemic administration of muscarinic agents. Therefore, muscarinic cholinergic regulation of basal and stimulated expression of neuropeptide mRNA is processed within the striatum.

Quantitation of rodent catalepsy by a computer-imaging technique

Catalepsy is usually defined as a behavioral state in which an animal maintains an unnatural posture for an extended period of time. While numerous laboratory models have been developed for assessing catalepsy, a common problem encountered with most procedures is the difficulty in quantitating immobility. Measurement of catalepsy is still frequently subjective in nature. To eliminate this subjectivity, a computer-based technique was developed for quantitating catalepsy in mice and rats as measured on the elevated ring. The system consisted of a video camera that was focused on either three mice or two rats. Their behavior was recorded during a 5-min session on videotape that was subsequently transmitted to a Macintosh II microcomputer via a Scion Image-Capture 2 board. A modification of the NIH Image 1.17 public domain program allowed the image of the rat to be transformed to a purely black or white image by assigning pixel values of either 0 or 256. The subsequent captured image was preprocessed in an identical manner and each pixel was subtracted from its corresponding pixel in the previous frame. Thus, changes in animal posture between the two frames can be quantitated. One subtraction cycle (acquisition, bilevel processing, and subtraction) was repeated at an average rate of approximately one per second. To quantitate immobility by image analysis, each frame was subtracted from the previous frame during a 5-min session. The resulting data were sorted according to the magnitude of movement (number of changed pixels) and plotted vs. time.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for separate neuronal mechanisms for the discriminative stimulus and catalepsy induced by delta 9-THC in the rat

The cataleptogenic effect of delta 9-THC was compared to its discriminative stimulus effects in rats. The ED50s for the discriminative stimulus and catalepsy were 0.8 and 4.0 mg/kg, respectively, while their time courses were very similar. The ED50 of delta 9-THC for catalepsy in experimentally naive rats was not different from that in rats trained with the drug discrimination procedure, indicating that the cataleptogenic effect was not appreciably attenuated by long-term exposure to low doses of delta 9-THC. Pharmacologically, the catalepsy produced by delta 9-THC more closely resembled that of haloperidol than of morphine, since anticholinergic pretreatment eliminated the delta 9-THC-induced catalepsy while pre-treatment with naloxone had no effect. Although the cataleptogenic effect of delta 9-THC could be pharmacologically manipulated by anticholinergic pre-treatment, its discriminative stimulus effects were not changed in the same animals. These results demonstrate that distinctive mechanisms of action exist for these cannabinoid-induced behaviors.

The NMDA receptor antagonist MK-801 increases morphine catalepsy and lethality

Interactions between excitatory amino acids and opioids were examined by studying the ability of the noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 to affect morphine catalepsy and lethality. MK-801 (0.3 mg/kg) reduced the ED50 for morphine-induced catalepsy from approximately 30 mg/kg to less than 10 mg/kg, and reduced the LD50 for morphine from approximately 100 mg/kg to approximately 10 mg/kg. Lower doses of MK-801 did not affect morphine catalepsy or lethality. MK-801, in the absence of morphine, produced no catalepsy or lethality at doses up to 3.0 mg/kg; at 0.3 mg/kg MK-801 caused weaving, body rolling and ataxis, as previously described, while at 3.0 mg/kg animals appeared to lose muscle tone, becoming limp. These results demonstrate that blockade of NMDA receptors can dramatically potentiate morphine catalepsy and lethality, and suggest a potential dangerous interaction with opioids in the clinical use of NMDA receptor antagonists.

Neuroleptic-induced catalepsy as a model of Parkinson's disease. II. Effect of glutamate antagonists

Subcutaneous administration of fluphenazine elicits catelepsy that can be attenuated by the glutamate antagonists MK801 and phencyclidine (PCP). 3-[-(+)-2-carboxy piperazine-4-yl]-propyl-1-phosphanate (CPP) was found to be ineffective in this model. Intrastriatal injections of sulpiride or fluphenazine were also found to induce catalepsy which could be attenuated by MK801 and PCP. These results illustrate that nondopaminergic compounds might possibly be of value in the treatment of Parkinson's disease. Furthermore it was demonstrated that this paradigm can be utilized to investigate neurotransmitter interactions within the striatum. This was clearly emphasized by the observation that bilateral administration of MK801 into the striatum increased basal locomotor activity.

Blockade of excitatory neurotransmission in the globus pallidus induces rigidity and akinesia in the rat: implications for excitatory neurotransmission in pathogenesis of Parkinson's diseases

Bilateral microinjections of the selective N-methyl-D-aspartate (NMDA) antagonist, (-)-2-amino-7-phosphonoheptanoate (AP7), 0.02-0.5 nmol, into the globus pallidus and ventral-posterior portions of the caudate-putamen result in an increase in the muscle tone (rigidity) and catalepsy (akinesia) in rats. NMDA blocked the actions of AP7 on motility in sensitive regions of the globus pallidus and caudate-putamen. Topographical differences in the action of AP7 in the striatum were detected in the dorsal-ventral and rostral-caudal direction. Microinjections of AP7 into the nucleus accumbens induced neither an increase in the muscle tone nor catalepsy in rats, while ventral regions of the caudate-putamen were sensitive to both actions of AP7. Microinjections of AP7 into the dorsal caudate-putamen resulted in a moderate or no increase in the muscle tone. AP7 failed to induce catalepsy from dorsal regions of the caudate-putamen. These data identify the globus pallidus and a defined subregion of the caudate-putamen as crucial sites where excitatory neurotransmission acts to regulate the final set-point of the respective output neurons providing modulation of the passage of motor information through the basal ganglia.