Renal function during onset of carbachol-induced hypertension in conscious rats

This study evaluated the changes in renal function that occur during the early phases of chronic infusion of carbachol into the lateral ventricle in conscious rats. Infusion of 1.0 micrograms/h of carbachol i.c.v. resulted in a prompt pressor response with mean arterial pressure rising 20 mm Hg within 15 min. The pressure remained elevated for the duration of a 2-hour infusion. Carbachol infusion at 0.5 micrograms/h induced a similar elevation in blood pressure, but the onset was delayed, reaching significance only after 30-60 min. The higher dose of carbachol was associated with a marked and sustained natriuresis, with sodium excretion increasing from 2.1 +/- 0.3 to 5.3 +/- 1.0 microEq/100 g min after 2 h, compared to 2.0 +/- 0.5 and 1.8 +/- 0.3 microEq/100 g min in vehicle-infused control animals. Sodium excretion did not change significantly in animals infused with carbachol at 0.5 microgram/h. There were no significant changes in glomerular filtration rate in any of the groups. Plasma levels of atrial natriuretic peptide (ANP) were not altered significantly by ventricular infusion of carbachol (188 +/- 99 before vs. 83 +/- 17 pg/ml after infusion). It is concluded that the pressor response to central carbachol infusion is not dependent on retention of sodium and water. The natriuresis observed with carbachol infusion can be dissociated from the pressor response, and is not mediated by ANP.     

Calcium Concentration-dependent Mechanisms through which Ketamine Relaxes Canine Airway Smooth Muscle

Background: Ketamine is a potent bronchodilator that, in clinically used concentrations, relaxes airway smooth muscle in part by a direct effect. This study explored the role of calcium concentration (Ca2+) in this relaxation.

Methods: Canine trachea smooth muscle strips were loaded with the fluorescent probe fura-2 and mounted in a spectrophotometric system to measure force and intracellular calcium concentration ([Ca2+]i) simultaneously. Calcium influx was estimated using a manganese quenching technique. Cyclic nucleotides in the airway smooth muscle strips were measured by radioimmunoassay.

Results: In smooth muscle strips stimulated with submaximal (0.1 micro Meter) and maximal (10 micro Meter) concentrations of acetylcholine, ketamine caused a concentration-dependent decrease in force and [Ca2+]i. The sensitivity of the force response to ketamine significantly decreased as the intensity of muscarinic receptor stimulation increased; the median effective concentration for relaxation induced by ketamine was 59 micro Meter and 850 micro Meter for tissue contracted by 0.1 micro Meter or 10 micro Meter acetylcholine, respectively (P < 0.05). In contrast, the sensitivity of the [Ca2+] sub i response did not depend on the intensity of muscarinic receptor stimulation. Ketamine at 1 mM significantly inhibited calcium influx. Ketamine did not significantly increase cyclic nucleotide concentrations.     

Use of latex agglutination testing in diagnosing pediatric meningitis.

BACKGROUND. Latex agglutination (LA) tests are ordered frequently on cerebral spinal fluid (CSF) specimens obtained from pediatric patients to identify pathogenic bacteria as early as possible in an acute infection. METHODS. Six hundred ten LA tests were performed on 176 patients suspected of having meningitis. RESULTS. Five patients with meningitis had positive LA tests. We found that the CSF white blood cell (WBC) count, and differential were the best predictors of meningitis. CONCLUSIONS. By limiting the use of LA tests to those patients having CSF with abnormal WBC counts or with positive Gram stains, the number of tests ordered would have been reduced. This practice would greatly reduce laboratory expense.     

Dopaminergic and serotonergic function following isolation rearing in rats: study of behavioural responses and postmortem and in vivo neurochemistry.

This series of experiments compared isolation-reared and socially reared rats for their locomotor activity, behavioural stereotypy, and monoamine function both postmortem and in vivo using intracerebral dialysis. In Experiment 1, isolates showed an altered time course of locomotor activity following d-amphetamine sulphate (AMPH) administration (0.5, 2.0, 3.0, or 5.0 mg/kg, SC). Isolation-reared rats also showed increased sensitivity to the sedative effects of a low dose of apomorphine hydrochloride (0.1 mg/kg) but did not differ from social controls following higher doses of the drug (0.5, 1.5, or 3.0 mg/kg, SC). Isolates showed a decrease in the intensity of apomorphine-induced stereotyped behaviours but no change in stereotypy induced by AMPH. In Experiment 2, isolates had higher postmortem dopamine (DA) concentrations and an altered asymmetry in DA function in the medial prefrontal cortex (PFC) but not in the nucleus accumbens (NAC) or caudate putamen (CPu). Isolated rats also had a lower 5-hydroxyindoleacetic acid (5-HIAA)/5-hydroxytryptamine (5-HT) ratio in the NAC (but not in the PFC or CPu) compared to controls. Experiment 3 used intracerebral dialysis to examine monoamine function in vivo following isolation rearing. Isolates showed greater increases in extracellular DA and greater decreases in DOPAC in response to 2 mg/kg AMPH SC in both the NAC and CPu. There were no apparent differences in the perfusate concentrations of either dopamine (DA), dihydroxyphenylacetic acid (DOPAC), or homovanillic acid (HVA) prior to drug administration. However, consistent with the results of Experiment 2, isolates had a reduced basal perfusate concentration of 5-HIAA from the NAC but not from the CPu. Experiment 4 measured postsynaptic DA function in CPu tissue slices following isolation. Isolation rearing did not affect cAMP accumulation in response to stimulation of D1 DA receptors by DA (0, 2.7, 9, or 30 microM). In addition, isolation rearing did not affect the coupling between D1 and D2 receptors, as measured by the increase in cAMP accumulation with 1 microM 2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1 H-3-benzazepin (SK&F 38393) and its reduction by 10 microM quinperole hydrochloride (LY 171555). These results are discussed in terms of the possible relationship between these neurochemical findings and the behavioural disturbances following isolation rearing of rats.