ABSTRACT
The hypothalamo-limbic system has been implicated in recognizing the affective significance of pain and elicitation of related emotional responses. Several evidences from different studies support a role of these areas in endogenous analgesic mechanisms for pain modulation as elucidated by different pain tests in more than one animal model. In the above context, the aim of this study was to investigate the relative effectiveness of the pain modulatory action of hypothalamic and limbic structures in rat using similar stimulation parameters, and studying the effect on tooth pulp stimulation evoked jaw opening reflex (TP-JOR). To achieve the objective, unilateral stimulation of hypothalamic (lateral = LH; ventromedial = VMN; anterior = AH) and limbic areas (amygdala = AMYG; hippocampus = HIPP) was done on the TP-JOR test. A significant reduction in the amplitude of EMG recorded from the digastric muscle (dEMG) as a result of tooth-pulp stimulation was observed on stimulation of LH, VMN, AMYG and HIPP but not from AH. Also, the magnitude of this effect was almost similar from these areas. The results suggest that these areas (except AH) have an antinociceptive role in tooth-pulp stimulation evoked pain response.
Subject(s)
Amygdala/physiology , Animals , Dental Pulp/physiology , Electric Stimulation , Electromyography , Hippocampus/physiology , Hypothalamic Area, Lateral/physiology , Hypothalamus/physiology , Limbic System/physiology , Male , Nociceptors/physiology , Pain Measurement , Rats , Rats, Wistar , Reflex/physiology , Ventromedial Hypothalamic Nucleus/physiologyABSTRACT
Feces of ventromedial hypothalamus (VMH) lesioned obese and sham operated (SL) rats were separately pooled and subjected to column chromatography using sephadex G-150. Fractions showing peak absorption at 280 nm, obtained from respective group of rats were separately pooled and divided into 9 equal aliquots and injected ip in two groups of overnight fasted normal rats (OFN rats). Rats injected with fecal extract from VMH lesioned rats showed decreased food and water intake which was not seen in rats treated with the fecal extract from SL rats suggesting the possible presence of an anorexigenic substance in the feces of VMH lesioned rats but absent in SL rats.
Subject(s)
Animals , Appetite Depressants/analysis , Feces/chemistry , Male , Rats , Rats, Wistar , Reference Values , Ventromedial Hypothalamic Nucleus/physiologyABSTRACT
The effect of ICV administered TSH on Brobeck's thermostatic hypothesis was evaluated by recording chronological changes in electrical activity of precise loci (POA, VMN and CO) coupled by rectal temperature changes in dogs. The study revealed 1. TSH action on thermoregulation is biphasic in nature. 2. This action of TSH is not an independent act but depends on the reaction of satiety centre.
Subject(s)
Animals , Appetite Regulation/physiology , Body Temperature , Body Temperature Regulation/physiology , Cerebral Cortex/physiology , Dogs , Electroencephalography , Injections, Intraventricular , Male , Preoptic Area/physiology , Thyrotropin/administration & dosage , Ventromedial Hypothalamic Nucleus/physiologyABSTRACT
Central effects of insulin on 20 min. food intake were studied in rats. Insulin administration in the lateral ventricular cerebrospinal fluid (CSF) did not alter food intake in the intact or lesioned ventromedial hypothalamus (VMH) rats. Whereas, after insulin injection in VMH there was a decrease in food intake. In VMH lesioned rats, subcutaneous injection of insulin increased food intake.
Subject(s)
Animals , Body Weight/drug effects , Eating/physiology , Injections, Intraventricular , Insulin/administration & dosage , Male , Rats , Ventromedial Hypothalamic Nucleus/physiologyABSTRACT
Hemos empleado 40 ratas macho, cepa Wistar, de 2 meses de edad. Los animales se dividieron en 20 ratas controles (10 ratas intactas y 10 ratas sometidas a operación simulada), y 20 animales experimentales (10 sacrificados al mes y 10 sacrificados a los dos meses de la operación quirúrgica). El método experimental fue la extirpación extereotáxica del nucleo amigdalino basolateral de la amígala cerebral. Hemos estudiado la ultraestructura del nucleo ventromedial del hipotálamo. Hemos observado un incremento de la actividad de las neuronas del nucleo hipotalámico ventromedial en los animales experimentales (aumento del retículo endodplasmático rugoso, del aparato de Golgi, de los cuerpos densos, y de las mitocondrias con matriz densa), y en las sinapsis (un incremento de las vesículas y de los gránulos densos). Nuestros resultados demuestran que el nucleo amigdalino basolateral ejerce un efecto inhibidor de la actividad neuronal del nucleo hipotalámico ventromedial