Biomedical vignette

Abstract

Although non-invasive identification of specific cerebral surface structures is crucial to clinical diagnosis and intervention, conventional MRI often fails to provide satisfactory outcome data due to the crude resolution of the tomographic slices [23]. Gong et al. [23] reported a new technique using MR-traced diffusion-weighted imaging that displays clear structures of the cerebral surface in normal subjects. They also obtained excellent results in mapping cerebral infarctions and their relation with cortical sulci/gyri in patients with acute or chronic cerebral infarcts. The high level of clarity in threedimensional visualization of cerebral surface structures offered by this new technique provides an additional dimension for diagnostic assessment and biomedical research, Dextromethorphan Potentiates Morphine-Induced AntinociceptionThe non-opioid antitussive, dextromethorphan, potentiates the analgesic effect of morphine and decreases the requirement of morphine for acute postoperative pain in rats [28] and patients [13]. Chow et al.[I6] studied the pharmacological mechanism that underlies these actions. Whereas potentiation of dextromethorphan on morphine-induced antinociception is observed via both intrathecaI and intracerebroventricular routes, neither 5-HT2 receptor nor %-adrenergic receptor antagonist elicits significant effect on this potentiation. These results suggest that serotoninergic or adrenergic descending paininhibitory pathways do not mediate the potentiating effect of dextromethorphan. Opioid Receptors Participate in Cardioprotection Induced by Cold-Restraint Stress or MorphineCold exposure is known to confer cardioprotection against ischemic insults. Whereas g-opioid receptor has been implicated in this process [33], the contribution of K-and b~-opioid receptors remains to be elucidated. Wu et aI. [70] demonstrated that cardioprotection conferred by cold and restraint stress or morphine is abolished by pretreatment with opioid receptor antagonists. Inhibition ot protein kinase C or blockade of mitochondrial KArp channel (both are hmwn [38,45] to play a role in preconditioning-induced cardioprotection) also reduces infarct size induced by myocardial ischemia/reperfusion. These results indicate the participation of all three opioid receptors, protein kinase C and mitochondriat KAr~ channel in cardioprotection induced by cold-restraint stress in the rat. Involvement of the Locus Ceruleus in Behavioral Changes Associated with Organophosphate InsecticidesExposures to organophosphate insecticides induce undesirable behavioral changes in humans, including anxiety and irritability, depression, cognitive disturbances, and sleep disorders [35]. Zhu et al.[75] delineated the underlying neural mechanisms by studying the role of the locus ceruleus (LC), a pontine site that contains high levels of acetylcholinesterase and is involved in regulation of the sleep-wake cycIe, attention, arousal, memory, and pathological processes, including anxiety and depression [22]. They reported that methyl parathion, a co...