ABSTRACT
Central glutamatergic relays are known to be present in the central sympathetic pathways. Ifenprodil (an N-methyl-D-aspartate antagonist) and baclofen (a gamma-aminobutyric acid(B) agonist) are both modulators of these synapses; we previously reported their ability to reduce the cardiovascular responses induced by a central hypothalamic stimulation in rabbits. In this work, we investigated the actions of chronic treatments with these two drugs on the increase of myocardial oxygen demand induced by exercise in normotensive rats. Moreover, their effects on the baroreceptor heart rate reflex were observed. Male normotensive WKY rats were treated with placebo (two groups), baclofen, or ifenprodil for 14 days. They were then submitted to a progressively increased exercise test on a treadmill. In another three groups of animals, the same treatment was applied but, at the end, a baroreflex study was performed by the injection of phenylephrine (vagal component of the reflex) and of sodium nitroprusside (sympathetic component). Ifenprodil and baclofen reduced by nearly 50% the level of the increase of the rate x pressure product during exercise as compared with control rats. This effect appeared to be mainly due to a reduction of the hypertensive response. In the same conditions, neither baclofen nor ifenprodil significantly altered the baroreceptor heart rate reflex. The fact that these two drugs are capable of reducing the myocardial oxygen demand encourages us to test them in a model of myocardial ischemia associated with sympathetic hyperactivity.
Subject(s)
Baclofen/pharmacology , Excitatory Amino Acid Antagonists/pharmacology , GABA Agonists/pharmacology , Myocardium/metabolism , Oxygen Consumption/drug effects , Oxygen Consumption/physiology , Physical Exertion/physiology , Piperidines/pharmacology , Animals , Baroreflex/drug effects , Baroreflex/physiology , Blood Pressure/drug effects , Blood Pressure/physiology , Exercise Test , Male , Rats , Rats, Inbred WKY , Receptors, Glutamate/physiology , Synapses/drug effects , Synapses/physiologyABSTRACT
The purpose of this study was to verify statistically the existence of certain characteristics of rapid eye movement (REM) production during REM sleep: organization and rhythmicity. REM data were collected intermittently, over a period of 20 consecutive nights, from 6 normal adult subjects of both sexes. Results concerning the organization of REM production revealed the presence of 3 evolving slow trends: quadratic, linear and quasi-sinusoidal. The occurrence of a given trend type was not related to subject, night, time of night or length of REM sleep phase being analysed. Results of the analysis showed that it is possible for a series of REMs to contain one, two or more statistically significant rhythmic periods, or no significant rhythmic period. The rhythmic periods that were detected ranged from 1 to 21 min, and no predominant periods were present. As in the case of the slow trends, the occurrence of a given rhythmic period was not dependent on subject, night, time of night or length of the REM sleep phase.
