Regional changes in brain cholinergic enzyme activities after bilateral olfactory bulbectomy in relation to mouse-killing behavior by rats

Behavior and the cholinergic parameters in olfactory bulbectomized female rodents: Difference between rats and mice

Olfactory bulbectomy (OBX) in rodents induces a wide spectrum of functional disturbances, including behavioral, neurochemical, and neuromorphological alterations. We have examined the effects of OBX on behavior and the parameters of the cholinergic system in female rats and mice. In rats, OBX resulted in the appearance of some depressive-like behavioral marks, such as the decreased sucrose consumption, hyperactivity, impaired short-term memory and anxiety-like behavioral features, such as shortened presence in the center of the open field arena or open arms of the elevated plus-maze and an enhancement of avoidance behavior. These behavioral abnormalities could be associated with disturbances in hippocampal function, this suggestion being supported by the presence of cellular changes in this brain structure. No effect of OBX on the number of cholinergic neurons in the medial septum-diagonal band as well as on the acetylcholine content and acetylcholinesterase activity in the septum, hippocampus, and neocortex could be detected. In contrast, in mice, OBX impaired spontaneous alternation behavior and decreased the number of cholinergic neurons in the medial septum-diagonal band. These data demonstrate that rats and mice differently respond to OBX, in particular, OBX does not significantly affect the cholinergic system in rats.

Brain output dysregulation induced by olfactory bulbectomy: an approximation in the rat of major depressive disorder in humans?

Mounting evidence indicates that the emotional, cognitive, neurovegetative and behavioral symptoms of patients with major depressive disorder are due to abnormal neurochemical substrates in the brain. Although the specific neurochemical abnormalities responsible have not been identified, the presenting symptoms of major depression are consistent with a disruption of normal neural communications between the limbic system and hypothalamus. Following removal of the olfactory bulbs, rats display a syndrome of behavioral deficits that also reflect a disruption of the limbic-hypothalamic axis. Moreover, the bulbectomy induced deficits are selectively reduced by the chronic administration of the same drugs that alleviate the symptoms of depression when given chronically to the patients. In addition to this pharmacological similarity, there are also numerous behavioral parallels between bulbectomized rats and major depression patients. The bulbectomized rat provides a good model in which to study antidepressant drugs and also may provide neurochemical and neuroanatomical data that are relevant to understanding the biological substrates of emotion and the causes of depression in humans.

Anti-muricide mechanisms of chlorpromazine and imipramine in OB rats: Adrenoceptors and hypothalamic functions

Chlorpromazine (CPZ) microinjected into the posterior part of the lateral hypothalamus (p-LH) and the lateral preoptic area (1-POA) of OB rats shows anti-muricide and cataleptogenic effects as well as a drowsy pattern in cortical EEG, while imipramine (IMP) injected into p-LH shows anti-muricide and cataleptogenic effects without change of cortical EEG. The present study examined the effects of drugs injected into p-LH and 1-POA on muricide, catalepsy and cortical and limbic EEG. CPZ (20, 50 micrograms) suppressed muricide and induced catalepsy and an EEG drowsy pattern in the two regions. The effects of CPZ in p-LH were similar to those of propranolol (PRO). In 1-POA, the anti-muricide effect of CPZ was similar to that of phenoxybenzamine, whereas the cataleptogenic and EEG effects were similar to those of PRO. IMP (10, 20 micrograms) in p-LH showed anti-muricide and cataleptogenic effects and induced a slight drowsy pattern in limbic EEG. The effects were similar to those of atropine. Lidocaine did not show any effects in the two regions. The cataleptogenic effects of CPZ and IMP did not appear related with the anti-muricide effects. The results suggest that the anti-muricide effect of CPZ in the hypothalamus depends on its adrenoceptor blockage, while that of IMP relates to its anticholinergic effect. In addition, beta-receptors in the hypothalamus appear related to the arousal system and dopaminergic functions.