Subject(s)
Neurons/physiology , Aging/drug effects , Animals , Axons/drug effects , Cats , Circadian Rhythm/drug effects , Drug Resistance , Electric Stimulation , Estrus/drug effects , Female , Humans , Iontophoresis , Learning/drug effects , Learning/physiology , Male , Neurons/drug effects , Rats , Receptors, Neurotransmitter/drug effects , Sex Characteristics , Species Specificity , Stimulation, Chemical , Stress, Physiological/physiopathologyABSTRACT
In waking rats and rabbits systemically injected angiotensin II was shown to participate predominantly in the mechanisms of negative emotional reactions. The effects of angiotensin II were observed at the behavioural level as well as at the neuronal one. Depending on the dose and the time of injection of angiotensin II and its specific antagonist saralasin they inhibited or facilitated elaboration and extinction of automatized conditioned active avoidance independently of arterial, pressure changes, the pain threshold being altered. Injection of angiotensin II abolished individual behavioural reactions of the animals in response to stress factors and increased their resistability to emotional stress. The negative emotional reactions were found to induce changes of chemosensitivity of neurones of the parafascicular complex of the medial thalamus and the midbrain reticular formation during microionophoretic application of angiotensin II. A supposition is made about the increase of angiotensin II brain synthesis under conditions of emotional stress.
Subject(s)
Angiotensin II/physiology , Avoidance Learning/physiology , Brain/physiopathology , Conditioning, Operant/physiology , Stress, Psychological/physiopathology , Animals , Extinction, Psychological/physiology , Humans , Hypothalamus, Middle/physiopathology , Male , Rats , Reticular Formation/physiopathology , Saralasin/pharmacology , Thalamic Nuclei/physiopathologyABSTRACT
A study was made of the sensitivity of parafascicular neurons of the thalamus to angiotensin II (A-II) applied microiontophoretically. Almost half of the neurons investigated (48,5%) were discovered to be sensitive to the peptide. Stimulation of the ventromedial hypothalamus provoked marked changes in the pattern of the responses of parafascicular neurons of the thalamus to A-II. The data obtained suggest that the sensitivity of parafascicular neurons of the thalamus, the pattern of responses to biologically active substances may be altered dynamically under the influence of excitations evoked by stimulation of the hypothalamus.
Subject(s)
Angiotensin II/pharmacology , Thalamus/drug effects , Ventromedial Hypothalamic Nucleus/physiology , Animals , Electric Stimulation , Male , Neural Conduction/drug effects , Rabbits , Thalamus/physiologyABSTRACT
The influence of intraventricular injection of different doses of renin on the effects of electrical stimulation of the ventromedial hypothalamus was studied. Injection of renin (10 micrograms/kg) into the lateral ventricles of the brain of experimental animals elicited a prolonged elevation of arterial pressure and a decrease of the heart rate, while given in doses of 20 and 30 micrograms/kg it also provoked arrhythmias and ventricular extrasystoles, and a lowering of the threshold of ventromedial hypothalamus stimulation. It was found that under the central action of renin, a short-term stimulation of the ventromedial hypothalamus provoked ventricular extrasystoles.
