Effects of Bemitil on the Activity of Noradrenergic and Serotonergic Brainstem Neurons and on EEG of Awake Cats

Abstract

In experiments on five awake cats, we studied the effects of bemitil, a drug possessing psychostimulatory, antidepressive, and actoprotector properties (peroral introduction, 50 mg/kg), on the activity of neurons of the aminergic cerebral systems. Eleven noradrenergic (NA-ergic) neurons of the locus coeruleus (LC) and 11 serotonergic (ST-ergic) neurons of the nuclei raphe (NR) were examined. A control experimental series was carried out on 8 NA-ergic neurons of the LC and 8 ST-ergic neurons of the NR. Bemitil was found to exert opposite effects on the impulse activity of NA-ergic and ST-ergic brainstem neurons; it suppressed impulsation of LC neurons and increased the spiking frequency of NR neurons within certain time intervals after its introduction. Analysis of EEG showed that bemitil decreased the spectral power of the delta and theta activities, which was accompanied by behavioral relaxation.

Effects of Bemitil on Electrical Activity of the Aminergic Systems and Cerebral Cortex in Awake Cats

“…Throughout the experiment (especially within the final period) and also within 8 to 12 h after it had ended, we observed a sleepy state in the experimental cats, similarly to that observed in rats [5,6]; the animals refused to consume food and water. Therefore, bemitil manifested some anorectic properties.…”

“…To elucidate the effects of administration of bemitil, we successfully recorded and analyzed the activity generated by 15 presumably NA-ergic neurons of the LC and 14 STergic neurons of the RN, while under conditions of placebo control, we recorded and analyzed the impulsation generated by 12 neurons of each of these neuronal groups. Both NA-and ST-ergic neurons were identified according to the criteria described earlier [6]. Segments of EEG were recorded upon the action of bemitil or under control conditions in 29 and 24 cases, respectively.…”

“…One of such preparations is a derivative of benzimidazole, bemitil; this agent is rather extensively used in clinics (to provide correction of the mental state in humans). At the same time, it should be recognized that single studies dealt with the detailed elucidation of the effect of this agent on the nervous system [4][5][6]. This is why our investigation is, in some aspects, pioneering.…”

“…In stress tests on rats, systemic injections of bemitil resulted in multidirectional modulation of behavioral acts depending on the dose of this agent [5]. In experiments on awake cats [6,7], systemic injections of bemitil in doses of 50 and 100 mg/kg exerted activating effects on supposedly serotonergic (ST-ergic) neurons of the raphe nuclei (RN) and suppressed impulsation of noradrenergic (NA-ergic) neurons of the locus coeruleus (LC). In these experiments, we also found that bemitil exerts a modulatory effect on the background EEG of these animals.…”

“…In addition, we compared the effects of bemitil used in different doses, namely 150, 100, and 50 mg/kg (earlier, we used lower doses [6][7][8]). …”