PubMed · 14975995
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Hannes Gruber, Gerd Bodner. 2004. Why CT-guided?. https://doi.org/10.2214/ajr.182.3.1820824
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RATIONALE: Although positive GABA(A) modulators can attenuate several cocaine-induced behavioral effects, there is a paucity of data on their interaction with cocaine on transition behavior or learning. OBJECTIVES: The current study examined the effects of cocaine (3.2-32 mg/kg), pregnanolone (3.2-24 mg/kg), and lorazepam (0.1-10 mg/kg) alone and in combination in rats responding under a multiple schedule of repeated acquisition and performance. METHODS: In the acquisition component, subjects acquired a different three-response sequence each session, whereas in the performance component, they responded on the same three-response sequence each session. RESULTS: All three drugs produced dose-dependent rate-decreasing and error-increasing effects. Cocaine was the least effective in decreasing rates and the most effective in increasing the percentage of errors. In combination with pregnanolone (3.2 or 10 mg/kg), the rate-decreasing effects of cocaine were relatively unchanged in both components, but 3.2 mg/kg of pregnanolone enhanced its error-increasing effects and the 10-mg/kg dose produced a significant dose-dependent interaction on errors. The combination of cocaine with lorazepam (0.32 mg/kg, 70-min pretreatment) produced significantly greater rate-decreasing and error-increasing effects than cocaine alone. A 15-min pretreatment with the same dose of lorazepam enhanced the error-increasing effects of small doses and attenuated the effects of larger doses of cocaine. Combinations of pregnanolone and lorazepam produced greater rate-decreasing and error-increasing effects in both components than either drug alone. CONCLUSIONS: The present data show that cocaine is more disruptive to learning in rats than pregnanolone or lorazepam, and that the disruptive effects of cocaine can be enhanced by CNS depressants.
Different crystalline forms of the local anaesthetic mepivacaine hydrochloride (MH) were revealed by Fourier transform infrared spectroscopy (FT-IR), not by conventional differential scanning calorimetry (DSC). The existence of two polymorphic anhydrous modifications was discovered and further characterized by X-ray powder diffraction and thermal analysis: Form II, the commercial one, and the more stable Form I, obtained by re-crystallization from Form II. Two pseudopolymorphs were also obtained: Form III, a solvate crystallized from ethanol and Form IV, a solvate crystallized from methanol. Single crystal X-ray diffraction data for both solvates were collected and their structures were determined. Form II, metastable and monotropically related to Form I, generates through desolvation of Form III, very often present in industrial processing, where crystallization from ethanol solution is a common practice. For the sake of clarity, the presence of polymorphic forms should be reported in the drug master files of MH. However, since MH is readily water soluble, the observed polymorphism has no relevance to its typical clinical use as aqueous solutions.
The cerebral cortex influences subcortical processing. In the somatosensory system, descending cortical inputs contribute in specific ways to the sizes and plasticity of tactile receptive fields (RFs) in the thalamus, but less is known about cortical influences on these aspects of brainstem RFs. The present studies evaluated how loss of cortical inputs affects sizes and plasticity of RFs in the brainstem dorsal column nuclei (DCN) when peripheral inputs were normal and when peripheral inputs were acutely disrupted. Loss of cortical inputs was produced by acute lesion of somatosensory, motor, and adjacent cortex, whereas disruption of peripheral inputs was produced by cutaneous microinjection of lidocaine (LID). Modest or no changes in sizes of DCN RFs, comparable to changes during control periods of no treatment, were seen in response to cortical lesion. LID caused rapid enlargements in RFs when cortex was intact. LID also caused rapid RF enlargements after cortical lesion, and these enlargements were greater than post-LID enlargements when cortex was intact. These results indicate that normally sized RFs continue to be produced in the DCN after loss of cortical input. Cortex is also not required for RF enlargements after LID; however, cortical inputs have a constraining effect on these enlargements. Considered with findings from previous thalamic studies, these results suggest that cortical influences on RF size and plasticity in the DCN and thalamus differ in some respects.