Cardiovascular effects of catecholamines injected into the DBB of rats, influence of urethane anaesthesia and local colchicine

A Hypothesis Regarding Neurosecretory Inhibition of Stress Mediators by Colchicine in Preventing Stress-Induced Familial Mediterranean Fever Attacks

Familial Mediterranean fever (FMF) is a monogenic autoinflammatory disease characterized by recurrent episodes of fever and serositis. Colchicine (Col) has a crucial role in the prevention of amyloidosis and FMF attacks. The effect of Col on innate immune cells is based on the inhibition of the microtubule system. The microtubule system is also very important for neurosecretory functions. The inhibitory effect of Col on neurosecretory functions is an overlooked issue. Considering that the neuroimmune cross-talk process plays a role in the development of inflammatory diseases, the effect of Col on the neuronal system becomes important. FMF attacks are related to emotional stress. Therefore, the effect of Col on stress mediators is taken into consideration. In this hypothetical review, we discuss the possible effects of Col on the central nervous systems (CNS) and peripheral nervous systems (PNS) in light of mostly experimental study findings using animal models. Studies to be carried out on this subject will shed light on the pathogenesis of FMF attacks and the other possible mechanisms of action of Col apart from the anti-inflammatory features.

Interaction between glutamatergic and nitrergic mechanisms mediating cardiovascular responses to l-glutamate injection in the diagonal band of Broca in anesthetized rats

In a previous study, we reported depressor and bradycardiac responses after L-glutamate (L-glu) microinjection into the diagonal band of Broca (dbB) in anesthetized rats. Here, we report the glutamatergic-receptor subtype mediating the cardiovascular effects evoked by L-glu injection into the dbB and the involvement of local nitric oxide (NO) mechanisms as well as peripheral effectors. Microinjections of 100 nL of L-glu (1, 27, 81, 130 or 200 nmol) into the dbB of urethane-anesthetized rats caused short-lasting depressor and bradycardiac responses. Responses were dose-related, with an ED(50) of approximately 81 nmol. This dose was used in later experiments. The cardiovascular responses to L-glu in the dbB were abolished by local pretreatment (100 nL) with the selective N-methyl-D-aspartic acid (NMDA) receptor antagonist LY235959 (4 nmol) but were not affected by pretreatment with the selective non-NMDA receptor antagonist NBQX (4 nmol). Responses to L-glu in the dbB were blocked by local pretreatment with the selective neuronal NO-synthase (nNOS) inhibitor N(omega)-propyl-L-arginine (NPLA, 0.04 nmol); the NO scavenger carboxy-PTIO (C-PTIO, 1 nmol) or the guanylate cyclase inhibitor ODQ (1 nmol). These results suggest that the microinjection of L-glu into the dbB of urethane-anesthetized rats causes dose-related depressor and bradycardiac responses through the NMDA receptor-NO-guanylate cyclase pathway.

Comparison of urethane/chloralose and pentobarbitone anaesthesia for examining effects of bacterial lipopolysaccharide in mice

Although anaesthetics are widely used to alleviate stress in endotoxaemic animals, these drugs themselves may interfere with the effects of lipopolysaccharide (LPS). The effects of LPS on serum glucose, biochemical markers of hepatic, renal and pancreatic exocrine function, and lung myeloperoxidase (MPO) activity were compared using anaesthesia with either urethane/chloralose or pentobarbitone. Groups of 10-13 of C57B1/6 mice (22.3 +/- 0.18 g) were treated with 40 mg/kg LPS or the same volume of saline (10 mL/kg, i.p.) at time 0, Animals were anaesthetized either with urethane (1000 mg/kg) and chloralose (50 mg/kg) or with pentobarbitone (90 mg/kg, i.p.) after 2 h and blood and lung samples obtained after 6 h. In pentobarbitone-anaesthetized mice, LPS caused hypoglycaemia and increased serum levels of alanine aminotransferase (ALT), lipase and creatinine suggesting damage/dysfunction of liver, exocrine pancreas and kidney respectively. Lung tissue MPO activity, an indicator of neutrophil infiltration, was also increased. Urethane/chloralose-treated mice demonstrated hypoglycaemia and enhanced serum levels of ALT and creatinine in response to LPS, but failed to show LPS-induced increases in serum lipase and lung MPO activity. It is concluded that while pentobarbitone may be successfully used in experimental models of endotoxaemia in mice, anaesthesia with urethane and chloralose may protect mice against LPS-mediated damage/dysfunction in the exocrine pancreas and in the lung, and therefore, is not recommended in studies on endotoxaemic mice.

Pressor effects of L-glutamate injected into the diagonal band of Broca of unanesthetized rats

The diagonal band of Broca (dbB) is involved in central cardiovascular control. In the present study we compared the effects of microinjections of L-glutamate into the dbB of unanesthetized rats with those observed after the injection of L-glutamate into the same area in urethane-anesthetized rats. The microinjection of L-glutamate (10, 30, 100 or 200 nmol/200 nl) into the dbB of urethane-anesthetized rats caused dose-related short-lasting depressor responses The depressor responses to L-glutamate were accompanied by dose-related heart rate reduction. The cardiovascular response to the injection of L-glutamate (10, 30 or 100 nmol/200 nl) into the dbB of unanesthetized rats was characterized as a long-lasting pressor response without consistent heart rate changes. The pressor response was dose-related and presented an ED(50) of approximately 30 nmol/200 nl. The fact that the chemical stimulation of the dbB with L-glutamate caused only dose-related pressor responses in unanesthetized rats suggests that under normal conditions the dbB is predominantly a pressor area. After the characterization of the pressor response to L-glutamate microinjected into the dbB of unanesthetized rats we studied the mechanisms involved in the mediation of these responses. The pressor response to L-glutamate (30 nmol/200 nl) into the dbB was blocked by intravenous pretreatment with the vasopressin antagonist dTyr(CH(2))(5)(Me)AVP (50 microg/kg), suggesting the involvement of circulating vasopressin in this response. Further evidence of the involvement of the endocrine vasopressin system in the pressor response to L-glutamate injected into the dbB was provided by hypophysectomy since L-glutamate (30 nmol/200 nl) microinjection into the dbB of hypophysectomized rats caused only depressor responses. We presently report that chemical stimulation of the dbB with L-glutamate caused only pressor responses in unanesthetized rats that were mediated by vasopressin release into the systemic circulation. Additionally, the results confirmed the existence of an L-glutamate-sensitive depressor system in the dbB, which is predominant in urethane-anesthetized rats or may be evidenced in unanesthetized hypophysectomized rats.

Acute effects of pentobarbital, thiopental and urethane on lung oedema induced by alpha-naphthythiourea (ANTU)

This study was designed to investigate the possible participation of urethane, pentobarbital sodium and thiopental sodium anaesthesia in the lung oedema induced by alpha-naphthylthiourea (ANTU), which is a well known noxious chemical agent in the lung. ANTU when injected intraperitoneally (i.p.) into rats (10 mg x kg (-1) i.p.) produced lung oedema as indicated by an increase in lung weight/body weight (LW/BW) ratio and pleural effusion (PE) reaching a maximum within 4 h. Administration of urethane prior to ANTU, at doses of 100 and 200mg(100g)(-1), elicited a significant and dose-dependent inhibition in LW/BW ratio and PE. Thiopental sodium at doses of 25, 50 mg x kg (-1), also produced a significant and dose-dependent inhibition of both parameters. Prior i.p. injection of pentobarbital sodium at a dose of 40 mg x kg (-1) elicited a significant inhibition in both parameters. These results suggest that i.p. urethane, thiopental sodium and pentobarbital sodium pretreatment have a prophylactic effect on ANTU-induced lung injury in rats. The possible role of the anaesthetics in lung oedema induced by ANTU and the possible underlying mechanisms are discussed.