Carotid glomectomy in rats reduced daily water consumption and increased daily consumption of NaCl solution. Sham operation did not modify water and salt consumption. Intraperitoneal injection of angiotensin-II did not stimulate drinking motivation in the majority of rats subjected to carotid glomectomy. Injection of angiotensin-II to sham-operated and intact animals induced active consumption of both fluids during one hour. These results attest to the involvement of the carotid body in the regulation of consumption of water and sodium ions (the main elements of osmotic blood pressure) and the involvement of angiotensin-sensitive receptors of carotid body cells in the formation of thirst and salt appetite motivation, regulated by the renin-angiotensin system.
In contrast to normal environmental conditions (normal temperature and gaseous composition of the atmosphere), regular exposure to hypoxia or cold for 3 weeks after carotid glomectomy does not increase blood glucose and causes no anemia or depression of gaseous and energy metabolism. Diabetogenic effect of streptozotocin after a previous hypoxic or cold exposure is associated with lower hyperglycemia; the time com~e of hematological and gaseous metabolism parameters after glomectomy depends on the effects of changed gaseous environment or temperature.The physiological significance of sinocarotid reflexogenie zones in neurohumoral regulation of the glucoreceptor function of the carotid chemoreceptors [8,10] prompted us to measure the level of glycemia and the main parameters of red blood and gaseous exchange in glomectomyzed diabetic animals under conditions of normoxia, hypoxia, and hypothermia.
Bilateral glomectomy in albino rats produced protective effect against the development of eorazol seizures, which was manifested in prolonged latency of seizures and a 2-fold shortening of their total duration. Acute hypoxia led to shortening of the latency both in glomeetomized and in sham-operated rats and significantly decreased the number of seizures in glomectomized rats, although a similar decrease in sham-operated rats was insignitieant. Poss~le participation of sinocarotid reflexogenie zones in hypoxic protection against experimental seizures is discussed.Key Words: corazol seizures; hypoxia; carotid glomectomy Pathogenic therapy of epilepsy is aimed at annihilating a pathological system by activation of natural resources and reflex regulatory mechanisms. Considerable attention has been focused on the possibility of inhibiting the activity of diverse functional systems inducing various disturbances in the central nervous system (CNS) by activation of the "anti-systems" [9]. This approach is based on natural functional antagonism between specific structures in the CNS. Some cerebral structures whose stimulation inhibits convulsive activity have been identified. There is evidence that "anti-systems" can be activated not only by electrical stimulation or pharmacological treatment, but also by hypoxia. Adaptation to hypoxia enhances the resistance to seizures [3,10] and decreases the number of fatal outcomes during the fits [8]. Both chronic and acute hypoxia produce protective effect against corazol seizures [4,6]. Our aim was to study a possible participation of sinocarotid retlexogenie zones in the realization of the protective effect of acute hypoxia during the development of experimental seizures.Department of Normal Physiology, Institute of Peoples' Friendship, Moscow MATERIALS AND METHODSThe study was carried out on 46 male albino rats weighing 220-240 g. In the first series of experiments, which was carded out on day 14 after bilateral carotid body excision (glomectomy) [71 or sham operation, the following parameters of convulsive activity induced by a single subcutaneous injection of corazol (60 mg/kg) were measured in 11 glomectomized (GE) and 15 sham-operated (SO) rats: latent period (LP) of the f'Lrst seizure, duration of a single seizure, number of seizures, and total duration of all seizures. In the second series of experiments, these parameters were measured on the same postoperation day for convulsive activity provoked by analogous injection of corazol in 10 GE and 10 SO rats kept under acute hypoxia in an altitude chamber with Po2=l10 mm Hg (3200 m above the sea level). RESULTSInjection of corazol under normoxia revealed a clear tendency to prolongation of LP and significant shortening of the total duration of seizures in GE rats as compared to SO rats: while the number of seizures was the same in both groups, the duration 0007-4888/98/0009-0876520.00 9Kluwer Academic/Plenum PubLishers
Systemic administration of angiotensin II after carotid glomectomy produced a less pronounced dipsogenic effects (consumption of water and NaCl solution) compared to sham-operated control animals. Injection of angiotensin II into the lateral cerebral ventricles of the same glomectomized rats increased water and NaCl consumption to a level surpassing that of sham-operated animals. The number of drinking acts and comfortable grooming acts decreased in glomectomized animals after systemic administration of angiotensin II, but increased after its intracerebral injection compared to the control. The results confirm the hypothesis that carotid chemoreceptors, as the peripheral component of the renin-angiotensin system, participate in the mechanisms of angiotensin-induced thirst, "salt appetite", and associated behavioral forms (comfortable grooming) synergically with the central cerebral receptors.
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