The effect of ketanserin on cardiovascular reflexes in conscious normotensive and spontaneously hypertensive rats

The effect of ketanserin (3 mg/kg i.v.) on the baroreceptor heart rate reflex and the Bezold-Jarisch reflex was examined in conscious Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). In the control situation (before ketanserin treatment), reflex bradycardia in response to phenylephrine (baroreflex) and phenyldiguanide (Bezold-Jarisch reflex) were impaired in SHR as compared with WKY, while reflex tachycardia in response to nitroprusside was similar in the two groups. However, after ketanserin administration in SHR, there was a reversal of the baroreflex-mediated tachycardia in response to nitroprusside into a bradycardic response. The nitroprusside-induced bradycardia was not caused by the release of 5-HT stimulating chemosensitive vagal afferents since the 5-HT3 receptor antagonist MDL 72222 did not block this response. In the same SHR, the Bezold-Jarisch reflex evoked by phenyldiguanide and the phenylephrine-induced bradycardia were potentiated by ketanserin. All the above effects of ketanserin were less evident in the WKY. Ketanserin did not alter vagal efferent function in anaesthetized SHR since it did not affect bradycardia induced by electrical stimulation of the vagus nerve. Therefore, it is suggested that ketanserin has sensitised cardiac vagal afferent mechanisms in SHR, which led to a normalization of reflex bradycardic function to a level normally observed in conscious normotensive WKY (i.e. prior to ketanserin treatment).     

Adenosine – dopamine receptor interactions in the isolated rat nodose ganglion but not in membranes of dorsal vagal complex

The present study has employed in vitro electrophysiology and radioligand binding assays to determine whether dopamine and adenosine receptors interact with each other on rat vagal afferent neurons. Preincubation of the isolated rat nodose ganglion with the adenosine A_2a agonists CGS 21680 or DPMA (Both 1 μM) resulted in a functional antagonism of the ability of dopamine to depolarise the preparation. Specifically, the concentration-response curve to dopamine was significantly shifted to the right in the presence of CGS 21680 and DPMA. On the other hand, adenosine itself, A₁ and A₃ receptor agonists and ATP were all incapable of modulating the electrophysiological response to dopamine. In contrast to the nodose ganglion, CGS 21680 did not significantly affect the ability of the dopamine D₂ ligands quinpirole or raclopride to displace [¹²⁵I]NCQ298 binding to dopamine D₂ receptors in membranes prepared from rat dorsal brain stem. These data indicate the presence of an interaction between high affinity adenosine A₂ receptors and dopamine D₂ receptors on the soma of rat vagal afferent neurons, whereas the situation in the brain stem remains less clear. Received: 17 September 1996 / Accepted: 20 October 1996     

Acute intracerebroventricular injections of the mast cell degranulator compound 48/80 and behavior in rats

The intracerebroventricular (ICV) injection of the mast cell degranulator Compound 48/80 (2.5-2.0 micrograms/kg) produced a marked behavioral syndrome in normotensive rats. The behaviors included head and body shakes, paw tremor, excessive grooming, unusual posture and gait, mild diarrhoea, piloerection, extreme agitation and irritability to touch, and a later phase of sedation. The highest doses (15 and 20 micrograms/kg) also produced catalepsy and episodes of "barrel rolling" (continuous rolling of 1-8 turns around the longitudinal axis). These behaviors were observed for approximately 15-30 min although the sedation and catalepsy were maintained for 90-120 min. A second ICV injection of the 10 micrograms/kg dose of Compound 48/80 given 2 hr after an initial injection of this dose, produced a much reduced response and the numbers of head and body shakes, and episodes of paw tremor and grooming were between 20-30% of those produced by the first injection. The reduced effect of the second injection indicates that the behavioral effects of Compound 48/80 may arise from the acute degranulation of mast cells rather than direct effects on neuronal populations or the cerebral vasculature.     

Distribution of neuropeptide Y immunoreactivity in the rat basal ganglia: effects of excitotoxin lesions to caudate-putamen

The distribution of neuropeptide Y-like immunoreactivity (NPY-LI) within the rat basal ganglia was studied using microdissection with a sensitive radioimmunoassay, and excitotoxin lesions were made in an attempt to characterise the neurones containing NPY in this brain area. Immunoreactivity was unevenly distributed in the basal ganglia of control rats, with concentrations in the caudate-putamen (CP) and nucleus accumbens being appreciably higher than those found in the globus pallidus and substantia nigra (SN). Within the CP, immunoreactivity was concentrated in caudal and extreme rostral aspects. N-Methyl-D-aspartate lesions of the rostral CP significantly reduced immunoreactivity in this area, whilst levels in other regions of the basal ganglia were unaffected. Neurones containing NPY-LI are likely to be intrinsic to the CP and do not appear to project to the globus pallidus or SN.     

Lack of alpha-adrenoreceptor binding of [125I]BE2254 to rat basilar artery membranes

Rat basilar arteries do not contain classical alpha- or beta-adrenoreceptors as assessed by electrophysiological techniques even though these arteries are innervated by catecholamine-containing perivascular nerves. These arteries were therefore examined for their ability to selectively bind an alpha-adrenoceptor radioligand, [125I]BE2254 (2/beta/4-hydroxyphenyl)-ethylaminomethyl)-tetralone). For comparison, rat tail arteries were also studied as these are known to contain functional alpha-adrenoreceptors. It was found that basilar artery membranes had only one-third of the specific binding of tail artery membranes and this finding collaborates the electrophysiological data.     

Taiwanese Experiences: Elders with Dementia in Two Different Adult Day Service (ADS) Environments

Background: Researchers have demonstrated that adult day services (ADS) benefit elders with dementia and their caregivers, but they have also observed infantilization that diminishes personhood. Many ADS are socially constructed as places for incompetent elders, where clients are labeled as child-like dependents. Most ADS research has been performed in Western society; little is known about ADS in Asian countries. The Taiwanese Government seeks to expand ADS availability to meet the needs of an aging population; researchers must examine their ADS environments and practices to inform program development and expansion that supports respectful elder care.

Objectives: Elders’ experiences of daily life were examined within the physical and social environments of one social and one medical model ADS in Taiwan. The ecological model and place rules informed our research framework.

Methods: Ethnographic data were analyzed for themes reflecting our framework with attention to physical and social environment and staff–client interactions.

Results: The social model center included unique environmental features, such as a temple, indicating the purpose of different areas. Staff treated clients like family, sometimes to clients’ detriment, providing limited privacy and demanding compulsory activity participation. The medical model center with nurse's station and institutional furniture reflected a hospital-like environment and fostered a patient–nurse relationship. Staff inattention actually created opportunities for autonomy among some clients.

Conclusion and discussion: Physical features and social interactions within Taiwanese ADS reflected infantilization similar to that seen in the US and uniquely embedded within a traditional cultural background. Our findings reveal a tension between physical and social care features reflecting Eastern traditions of respect for elders and western traditions of institutional care.     

Tissue distribution and hypotensive effect of prazosin in the conscious rat

We investigated the hypotensive effect and tissue distribution of prazosin (1 mg/kg i.v.) in conscious rats. This dose caused an immediate fall in blood pressure, associated with a nonsignificant increase in heart rate. Blood pressure then gradually rose to control over a 2-h period. Prazosin was measured in plasma and tissue samples by high-pressure liquid chromatography. Highest concentrations of drug were found in liver and kidney and the lowest in brain. The rate of decline of prazosin from plasma was similar to its decline from the tissues, indicating a rapid equilibrium. This rate of disappearance was also similar to the decay of the hypotensive response and suggests that prazosin in plasma may be in equilibrium with prazosin at its site of action.     

Comparison of three assays for cytomegalovirus detection in AIDS patients at risk for retinitis

The purpose of this study was to determine the sensitivity and specificity of three different methods of cytomegalovirus (CMV) detection for AIDS patients at risk for CMV retinitis. Patients with CD4(+) counts of <100/microl and negative baseline screening eye examinations were tested for CMV infection by (i) pp65 antigenemia expression in leukocytes, (ii) the Digene Hybrid Capture CMV DNA System, and (iii) the Roche Amplicor Qualitative PCR Test. The incidence of CMV retinitis in our study of 296 patients at the Medical Center of Louisiana-New Orleans HIV Outpatient Clinic was 7. 2 per 100 person-years (a total of 20 episodes in 18 patients from April 1997 to February 1999). Receiver operating characteristic curves were calculated for each assay to determine optimal cutoff points which maximized the sensitivity and specificity of each assay. The sensitivities of the assays compared to the eye examinations were 80% for the pp65 antigenemia assay (cutoff, >0 cell per 1.5 x 10(5) leukocytes), 85% for the Digene assay (cutoff, 1,400 genome copies/ml of whole blood), and 60% for the Amplicor assay. The specificities of the assays were 84, 84, and 87%, respectively. The Digene assay with a cutoff of >/=1,400 genome copies/ml gave optimal sensitivity and specificity and was found to have predictive values equal to those of the more technically cumbersome antigenemia assay.     

Altered alpha 1-adrenoceptor-mediated responses in atria of rats with chronic left ventricular infarction.

Phosphoinositide (PI) turnover, chronotropic and inotropic responses to alpha 1-adrenoceptor activation, and alpha 1-adrenoceptor density were studied in atria from rats with left ventricular myocardial infarction (LVMI) and noninfarcted rats. LVMI was produced after surgical ligation of the left coronary artery in 8-week-old Wistar rats. Rats were killed 4 weeks after this operation when rats with LVMI had developed significant hypertrophy of both ventricles and atria. Phenylephrine 0.1 mM to 1 mM, with propranolol 0.3 mM, produced a concentration-dependent increase in heart rate (HR) in right atria from noninfarcted rat hearts, and this response was significantly reduced in rats with LVMI. In electrically driven left atria, the concentration-dependent, phenylephrine-induced positive inotropic responses observed with propranolol added were also significantly impaired in rats with LVMI as compared with those of noninfarcted rats. In contrast, neither PI turnover in response to phenylephrine in the presence of propranolol nor alpha 1-adrenoceptor density was reduced in rats with LVMI. These results suggest that the impaired alpha 1-adrenoceptor-induced chronotropic and inotropic responses in atria from rats with LVMI are not due to downregulation of alpha 1-adrenoceptors or to impaired activation of PI turnover after alpha 1-adrenoceptor stimulation, but to impairment of one or more biochemical responses distal to PI hydrolysis or changes in coupling mechanisms other than hydrolysis of PIs.