Regional differences in neurovascular coupling in rat brain as determined by fMRI and electrophysiology.

Increases in neuronal activity induce local increases in cerebral perfusion. However, our understanding of the processes underlying this neurovascular coupling remains incomplete and, particularly, how these vary across the brain. Recent work supports an important role for astrocytes in neurovascular coupling, in large part via activation of their metabotropic glutamate receptors (mGluR). Here, using a combination of functional magnetic resonance imaging (fMRI) and electrophysiology we demonstrate regional heterogeneity in the mechanisms underlying neurovascular coupling. Direct electrical stimulation of the rat hindpaw sensorimotor cortex induces blood oxygenation level dependent (BOLD) and cerebral blood volume (CBV) fMRI responses in several anatomically distinct cortical and subcortical structures. Following intraperitoneal administration of the type 5 mGluR antagonist, MPEP, both BOLD and CBV responses to cortical stimulation were significantly reduced, whilst the local field potential (LFP) responses remained largely constant. Spatially, the degree of reduction in fMRI responses varied between cortical and subcortical regions (primary cortex approximately 18% vs. striatum approximately 66%), and also between primary and secondary cortical areas ( approximately 18% vs. approximately 55%). Similarly, greater decreases in response amplitude were seen in the contralateral secondary cortex ( approximately 91%) and ipsilateral striatum (approximately 70%), compared to the primary cortex (approximately 44%). Following MPEP, a negative component of the BOLD and CBV responses became more apparent, suggesting that different mechanisms mediate vasodilatory and vasoconstrictory responses. Interestingly, under baseline conditions the quantitative relationship between fMRI and LFP responses in cortical and subcortical regions was markedly different. Our data indicate that coupling between neuronal and fMRI responses is neither empirically nor mechanistically consistent across the brain.

Use of niacin in the prevention and management of hyperlipidemia.

Niacin is an inexpensive drug useful in treating various forms of hyperlipidemia. Cardiac doses of niacin are effective in lowering serum triglyceride, low density lipoprotein, and lipoprotein-a levels and in elevating high density lipoprotein levels. Adverse reactions to niacin are varied and dose-dependent and range from annoying cutaneous flushing to hepatic toxicity. Patients advised to use the drug should be carefully screened and monitored. This paper reviews the pathologic and pharmacologic basis for niacin as an antilipemic agent. The biochemical and physiologic effects of the drug and its mechanisms of action are discussed. Emphasis is placed on the importance of aggressive management of serum lipids and the therapeutic uses of niacin. The use of niacin in primary and secondary prevention of heart disease is stressed. A patient education guide is included.

Assessing peripheral arterial disorders in the home: a multidisciplinary clinical guide.

Patients with peripheral vascular diseases (PVD) have venous problems, arterial problems, or both. Although several home care clinical guidelines exist for PVD, the multidisciplinary clinical guidelines for clients with peripheral arterial diseases outlined in this article present new material for nurses and agencies who are interested in developing clinical paths for these challenging patients.

Teaching the use of walkers and canes.

Home care and hospice nurses frequently encounter patients who use assistive devices to safely remain mobile in their homes. Incorrectly used, these devices may contribute to falls. This article provides a review on the use and teaching of these devices to patients and caregivers. A physical therapist, occupational therapist, or rehabilitation nurse should be consulted for any questions about applying the guidelines in this article to patients.

The antilipidemic effects of plain and extended-release niacin.

The extensive antihyperlipidemic effects of niacin are well known. Cardiac doses of niacin are effective in lowering low density lipoprotein, triglyceride, and lipoprotein(a) levels and in elevating high density lipoprotein levels. Adverse reactions to niacin range from annoying cutaneous flushing to hepatic toxicity. A new extended-release form of niacin (Niaspan) has been found to have relatively mild hepatic effects. Nighttime dosing of Niaspan appears to attenuate cutaneous flushing. Regardless of the form of drug prescribed, patients advised to use niacin should be carefully screened and monitored. Adverse effects of niacin are emphasized because of their particular importance in the provision of primary care. The dosing schedules for both plain niacin and extended-release niacin are discussed. (c) 2000 by CHF, Inc.