RESUMEN
Effects of bilateral electric lesion of the hypothalamic paraventricular nuclei on cardiovascular components of the defense response and on the self-stimulation operant behaviour, were studied in rats. Overloading of the highest nervous activity induced no hypertension in these animals, though the self-stimulation frequency increased.
Asunto(s)
Hipertensión/etiología , Núcleo Hipotalámico Paraventricular/fisiología , Autoestimulación/fisiología , Animales , Reacción de Prevención/fisiología , Enfermedad Crónica , Condicionamiento Clásico/fisiología , Estimulación Eléctrica , Electrodos Implantados , Hipertensión/fisiopatología , Hipotálamo Posterior/fisiología , Masculino , Ratas , Estrés Psicológico/complicaciones , Estrés Psicológico/fisiopatologíaRESUMEN
Neuronal organisation of hypothalamo-bulbar mechanisms of regulation of vascular tonus was studied in anesthetised and immobilised cats. The descending influence of posterior, tuberal and anterior structures of the hypothalamus on the activity of antidromically identified sympatho-activating reticulospinal neurons of the ventrolateral region of medulla oblongata is realised by mono-, oligo- and polysynaptic mechanisms. Chronic neurogenic hypertension was induced in rats by overloading the higher nervous activity. Arterial hypertension did not develop in chemically desympathized cats. Central and peripheral neurohumoral mechanisms of vascular tonus regulation are discussed.
Asunto(s)
Neurotransmisores/fisiología , Resistencia Vascular/fisiología , Potenciales de Acción/fisiología , Animales , Gatos , Condicionamiento Clásico/fisiología , Estimulación Eléctrica , Hipertensión/fisiopatología , Hipotálamo/fisiología , Bulbo Raquídeo/fisiología , Microelectrodos , Neuronas/fisiología , Ratas , Simpatectomía Química , Sistema Nervioso Simpático/fisiologíaRESUMEN
Effects of acute and chronic arterial hypertension on self-stimulation operant behaviour were studied in cats and rats. Small doses of noradrenaline facilitated the self-stimulation, whereas high doses depressed or stopped it. The depressive effect was accompanied by an obvious increase in the blood pressure. Chronic neurogenic hypertension can be induced by means of overloading the higher nervous system. A marked suppression of self-stimulation behaviour was found in chronic hypertensive rats. Decrease of the arterial pressure induced with an anti-hypertensive drug (catapresan) resulted in a temporary recovery of self-stimulation reaction. Baroafferent mechanisms of inhibition of positive emotional structures of the hypothalamus are discussed.
Asunto(s)
Hipertensión/fisiopatología , Hipotálamo/fisiopatología , Animales , Presión Sanguínea/efectos de los fármacos , Gatos , Masculino , Contracción Miocárdica/efectos de los fármacos , Norepinefrina/fisiología , Propranolol/farmacología , Ratas , Autoestimulación/fisiologíaRESUMEN
Effect of high-frequency stimulation of medial and lateral areas of the posterior, tuberal and anterior hypothalamus as well as of the periaqueductal gray (PAG) on jaw-opening reflex elicited with tooth-pulp stimulation, was studied in anesthetized cats. The m. digastricus EMG response was suppressed with stimulation of all hypothalamic structures. The threshold of the inhibitory effect was lower in the PAG stimulation. Hypothalamic stimulation-produced antinociception was reversed by the specific opiate antagonist naloxone, effect of PAG stimulation being less sensitive to naloxone. After bilateral lesion of PAG the antinociceptive effect of the hypothalamus was only slightly reduced. Complete inhibition of the EMG nociceptive response, similar to the effect of hypothalamus and PAG stimulation was induced with administration of an opiate agonist phenaridine.
Asunto(s)
4-Aminopiridina/análogos & derivados , Hipotálamo/fisiología , Dolor/fisiopatología , Reflejo/fisiología , Analgésicos/farmacología , Animales , Gatos , Naloxona/farmacología , Sustancia Gris Periacueductal/fisiologíaRESUMEN
The comparative effectiveness of the inhibitory influence of tetanic stimulation of hypothalamus, amygdala and limbic cortex on EMG-response of m. digastricus evoked by electrical stimulation of tooth pulp nociceptive afferents was studied in cats anesthetized with a mixture of chloralose and nembutal. It was found that inhibition of the EMG-component of the jaw-opening reflex is most pronounced in case of stimulation of medial and lateral region of the hypothalamus, the inhibitory effect of central and medial nuclei of the amygdala is less pronounced and the effect of the limbic cortex is the weakest. It was shown that the mechanism of the antinociceptive effect of tetanic stimulation of the hypothalamus is not related to the concomitant increase of the blood pressure. After stabilization of the blood pressure the suppressive effect of the hypothalamus remains without changes, that points out to a direct, primary, not baro-afferent mechanism of the inhibition of the activity of nociceptive neurons of the trigeminal sensory nuclei. Noradrenaline, injected intravenously, induced a large increase of the blood pressure accompanied by a pronounced inhibition of the pain reflex. Angiotensin causes the same degree of blood pressure elevation without changes in the amplitude of the EMG-response of the pain reflex. Hypothalamic and noradrenergic mechanisms for control of pain sensitivity are discussed.
Asunto(s)
Sistema Límbico/fisiología , Boca/fisiología , Inhibición Neural , Nociceptores/fisiología , Reflejo/fisiología , Potenciales de Acción/efectos de los fármacos , Angiotensina II/farmacología , Animales , Presión Sanguínea/efectos de los fármacos , Gatos , Pulpa Dental/fisiología , Estimulación Eléctrica/métodos , Electromiografía , Hexametonio , Compuestos de Hexametonio/farmacología , Sistema Límbico/efectos de los fármacos , Boca/efectos de los fármacos , Inhibición Neural/efectos de los fármacos , Nociceptores/efectos de los fármacos , Norepinefrina/farmacología , Reflejo/efectos de los fármacosRESUMEN
Responses of single units from lateral and medial areas of the posterior, tuberal and anterior hypothalamus to electrical stimulation of dental pulp and sciatic nerve A beta afferents were recorded in anesthetized curarized cats. 80.7%, 81.5% and 71.4% of units, respectively, responded to stimulation in posterior tuberal and anterior hypothalamus. The shortest latency of responses was recorded in the postero-lateral hypothalamus. Nociceptive responses in the lateral hypothalamus were of shorter latency than responses of medial hypothalamic units. Marked predominance of excitatory responses in the posterior hypothalamus and almost an equal proportion of excitatory and inhibitory responses in the tuberal and anterior hypothalamus were found. High degree of convergence (85.8%) of noxious and nonnoxious (sciatic nerve A beta afferents) impulses was revealed. Unidirectional, similar pattern of responses of convergent type neurons to stimulation of the tooth pulp and sciatic nerve A beta afferents indicate a nonspecific character of responses of the majority of polysensory neurons. 14.2% of hypothalamic units were monomodal, specific nociceptive neurons. Hypothalamic nociceptive units were characterized by a long recovery cycle (200-500 ms) and low reproducibility of responses to repetitive stimulation of the tooth pulp afferents (1.5-2/s). The neuronal organization of the nociceptive afferent system of the hypothalamus and the functional role of convergent and specific nociceptive neurons of the hypothalamus are discussed.
Asunto(s)
Pulpa Dental/fisiopatología , Hipotálamo/fisiopatología , Nociceptores/fisiología , Dolor/fisiopatología , Nervios Espinales/fisiopatología , Animales , Gatos , Estimulación Eléctrica , Potenciales Evocados , Hipotálamo Anterior/fisiopatología , Hipotálamo Posterior/fisiopatología , Tiempo de Reacción/fisiología , Nervio Ciático/fisiopatología , Tuber Cinereum/fisiopatologíaRESUMEN
The part of noradrenergic mechanisms in self-stimulation (SS) operant behaviour was studied in rats. In all experiments systolic blood pressure (BP) in the tail artery was measured by means of photocells. It was found, that small doses of noradrenaline facilitate the SS, while high doses depress or stop it. The depressive effect is accompanied by a marked increase of BP. Effective blockade of beta-adrenoceptive structures by inderal suppresses SS, and the inhibitory effect is accompanied by a small decrease of BP. Suppressing effect of alpha-adrenoblocking agent, phentolamine, is even more pronounced, but is accompanied by a marked decrease of BP. Beta-agonist isadrin causes a marked facilitation of SS without changes of BP. It is suggested that positive reward in the lateral hypothalamus is due to a direct stimulation of beta-adrenoceptive noradrenergic neuronal elements. Chronic neurogenic hypertension is developed by an overloading of the higher nervous activity. In chronic hypertensive rats there is a pronounced suppression of SS. A transient fail of BP caused by injection of catapresan (hemiton) results in a temporary recovery of normal SS behaviour. It may be concluded that reduction of lever-pressing rate during acute and chronic neurogenic hypertensions is related to baroreceptor mechanisms. The role of the autonomic nervous system in SS behaviour is discussed.