ABSTRACT
Initially a dose-response curve of phenylephrine was constructed at dose strengths of 1-16 microg/kg in a cumulative manner. Phenylephrine caused a significant rise in the mean arterial pressure, left ventricular systolic pressure, left ventricular contractility, stroke volume and a significant decline in the heart rate. Terazosin was administered in three selected doses of 10, 100 and 300 microg/kg. Following each dose of terazosin, dose-response curve of phenylephrine was constructed. Terazosin, per se, decreased the basal mean arterial pressure, left ventricular systolic pressure, left ventricular contractility and stroke volume significantly in a dose dependent manner with an increase in the heart rate with no significant change in the cardiac output. The baroreflex sensitivity at all the three doses remained unchanged. In conclusion, the present findings support the view that terazosin reduces the blood pressure in a physiologically more favorable manner by maintaining the neural integrity of the cardiovascular system.
Subject(s)
Adrenergic alpha-Antagonists/administration & dosage , Animals , Antihypertensive Agents/administration & dosage , Baroreflex/drug effects , Blood Pressure/drug effects , Cardiovascular Physiological Phenomena/drug effects , Dogs , Heart Rate/drug effects , Male , Phenylephrine/pharmacology , Prazosin/administration & dosage , Stroke Volume/drug effects , Ventricular Function, Left/drug effectsABSTRACT
Control of Intra Ocular Pressure (IOP) is influenced by both divisions (sympathetic and para-sympathetic) of Autonomic Nervous System (ANS). The present study was conducted to confirm existence of any association of ANS with primary open angle glaucoma (POAG), if present. Systemic autonomic function tests were assessed in fifty patients of POAG with fifty normal subjects matched for sex and age as control using several well established tests based on cardiovascular reflex responses to standardised stimuli viz. Resting heart rate (RHR), Corrected QT Interval (QTc), T-wave amplitude, Standing to Lying Ratio (SLR); Valsalva Ratio; Galvanic Skin Resistance (GSR) and Cold Pressor Test (CPR). Tests were conducted in the Department of Physiology, Maulana Azad Medical College and associated Glaucoma Clinic of Guru Nanak Eye Centre from june '94-May '95. Subjects were randomly chosen from known POAG cases with IOP--25 +/- 5.08 mm Hg. The results showed decrease in both sympathetic and para-sympathetic activity of autonomic function tests in POAG suggesting associated autonomic dysfunction. Sympathetic under-activity is seen in 36 patients out of 50 (73%), POAG subjects while para-sympathetic activity is decreased in 43 of 50 (86%) of the POAG subjects when compared with normal control group. The results help concluding that POAG is associated with autonomic dysfunction with decreased activity of both sympathetic and para-sympathetic divisions of ANS.
Subject(s)
Autonomic Nervous System Diseases/complications , Baroreflex , Case-Control Studies , Female , Galvanic Skin Response , Glaucoma, Open-Angle/complications , Heart Function Tests , Humans , Male , Ocular Hypertension/etiology , PressoreceptorsSubject(s)
Adult , Age Factors , Autonomic Nervous System/physiology , Blood Pressure , Electrocardiography , Female , Galvanic Skin Response , Heart Rate , Humans , Male , Middle Aged , Sex CharacteristicsABSTRACT
There is much clinical evidence to suggest that certain types of Glaucoma are related to activity of autonomic nervous system (ANS). Although some local changes have been documented but systemic association has not been established, so far. Hence, the present study was initiated and an attempt was made to bring out the association of systemic autonomic functions with glaucoma (especially Primary Closed Angle Glaucoma (PCAG)) if any. This study was carried out in the Department of Physiology, Maulana Azad Medical College in association with Glaucoma Clinic of Guru Nanak Eye Centre, New Delhi from June 1993-August 94. ANS function tests were conducted using Polyrite-8-Medicare System. The subjects were confirmed cases of PCAG with 10P-22.1 +/- 4.4 mmHg and possibility of autonomic neuropathy due to any other cause was ruled out. They were matched with normal subjects for their age, anthropometry and were compared for their sympathetic activity of ANS by Galvanic Skin Resistance (GSR); Cold Pressor Response (CPR); corrected QT interval (QTc) and T-wave amplitude (TWA) and for parasympathetic activity of ANS by Resting Heart Rate (RHR); Standing to Lying Ratio (SLR) and Valsalva Ratio and analysed statistically using standard 't' test. The results obtained in this study indicated increase in sympathetic activity in 61% of PCAG subjects and decreased parasympathic activity in 80% of the PCAG subjects when compared with control group of subjects, suggesting association of autonomic neuropathy with PCAG.