Involvement of the nitric oxide/cyclic guanylate monophosphate pathway in the pilocarpine-induced seizure model in mice.

The present study was designed to investigate the involvement of the nitric oxide (NO)/cyclic guanylate monophosphate pathway in pilocarpine-induced seizures in mice. Male Swiss mice (26-32 g) were used as the in vivo model. The following pharmacological tools were utilized: the non-selective NO synthase (NOS) inhibitor L-NAME (10 mg/kg, i.p.), a preferential inducible NOS (iNOS) inhibitor aminoguanidine (25 mg/kg, i.p.), a highly specific iNOS inhibitor 1400W (2.5 mg/kg, i.p.), the NO donor L-arginine (150 mg/kg, i.p.), and the soluble guanylyl cyclase inhibitor ODQ (10 mg/kg, i.p.). The animals were divided into groups (n = 8) and pretreated for 30 min before receiving pilocarpine (400 mg/kg, i.p.), while the control group received only pilocarpine. They were observed for 60 min to measure initial seizure latency, latency till death, and mortality. An administration of L-NAME or ODQ delayed the onset of initial seizure, increased latency till death, and produced a 25% survival rate. Aminoguanidine increased the initial seizure and latency until death, and administration of 1400W did not have an effect. Incremental increases of NO by L-arginine were capable of decreasing the seizure and death latency. These results support the idea that the constitutive NOS, probably neuronal NOS, followed by soluble guanylyl cyclase activation is involved in the convulsive responses caused by pilocarpine administration.

Proconvulsant effects of sildenafil citrate on pilocarpine-induced seizures: Involvement of cholinergic, nitrergic and pro-oxidant mechanisms.

Sildenafil is a phosphodiesterase 5 inhibitor used for the treatment of erectile dysfunction and pulmonary hypertension. Proconvulsant effect is a serious adverse event associated with sildenafil use. Here, we investigated the possible proconvulsant effects of sildenafil in pilocarpine (PILO)-induced seizures model, which mimics some aspects of temporal lobe epilepsy. We also evaluated sildenafil's effects on hippocampal markers related to PILO-induced seizure, for instance, acetylcholinesterase (AChE) activity, oxidative stress and nitric oxide (NO) markers, namely nitrite, inducible NO synthase (iNOS) and neuronal NOS (nNOS). The influences of muscarinic receptors blockade on sildenafil proconvulsant effects and brain nitrite levels were also evaluated. Male mice were submitted to single or repeated (7 days) sildenafil administration (2.5, 5, 10 and 20 mg/kg). Thirty minutes later, PILO was injected and mice were further evaluated for 1 h for seizure activity. Sildenafil induced a dose- and time-progressive proconvulsant effect in PILO-induced seizures. Sildenafil also potentiated the inhibitory effect of PILO in AChE activity and induced a further increase in nitrite levels and pro-oxidative markers, mainly in the hippocampus. Repeated sildenafil treatment also increased the hippocampal expression of iNOS and nNOS isoforms, while the blockade of muscarinic receptors attenuated both sildenafil-induced proconvulsant effect and brain nitrite changes. Our data firstly demonstrated the proconvulsant effect of sildenafil in PILO-model of seizures. This effect seems to be related to an increased cholinergic-nitrergic tone and pro-oxidative brain changes. Also, our findings advert to caution in using sildenafil for patients suffering from neurological conditions that reduces seizure threshold, such as epilepsy.

Neonatal Immune Challenge with Lipopolysaccharide Triggers Long-lasting Sex- and Age-related Behavioral and Immune/Neurotrophic Alterations in Mice: Relevance to Autism Spectrum Disorders.

Early-life challenges, particularly infections and stress, are related to neuropsychiatric disorders such as autism and schizophrenia. Here, we conducted a wide range of behavioral tests in periadolescent (postnatal day (PN) 35) and adult (PN70) Swiss mice neonatally challenged with LPS on PN5 and -7, to unveil behavioral alterations triggered by LPS exposure. Immune and neurotrophic (brain-derived neurotrophic factor-BDNF) alterations were determined in the prefrontal cortex (PFC), hippocampus (HC), and hypothalamus (HT). Since the incidence and clinical manifestations of neurodevelopmental disorders present significant sex-related differences, we sought to distinctly evaluate male and female mice. While on PN35, LPS-challenged male mice presented depressive, anxiety-like, repetitive behavior, and working memory deficits; on PN70, only depressive- and anxiety-like behaviors were observed. Conversely, females presented prepulse inhibition (PPI) deficits in both ages studied. Behavioral changes in periadolescence and adulthood were accompanied, in both sexes, by increased levels of interleukin (IL-4) (PFC, HC, and HT) and decreased levels of IL-6 (PFC, HC, and HT). BDNF levels increased in both sexes on PN70. LPS-challenged male mice presented, in both ages evaluated, increased HC myeloperoxidase activity (MPO); while when adult increased levels of interferon gamma (IFNγ), nitrite and decreased parvalbumin were observed. Alterations in innate immunity and parvalbumin were the main LPS-induced remarks between males and females in our study. We concluded that neonatal LPS challenge triggers sex-specific behavioral and neurochemical alterations that resemble autism spectrum disorder, constituting in a relevant model for the mechanistic investigation of sex bias associated with the development of this disorder.

HIV antiretroviral drug Efavirenz induces anxiety-like and depression-like behavior in rats: evaluation of neurotransmitter alterations in the striatum.

Efavirenz (EFV) is an effective antiretroviral drug with a favorable pharmacokinetic profile and widely used in combination regimens to treat HIV infection. However, there are major concerns about the safety of this drug. Patients treated with EFV often experience neuropsychiatric adverse effects, which frequently lead to switching to alternative EFV-free regimens. The mechanisms involved in the central action of EFV are intrinsically unclear. Thus, this study aimed to investigate the effects of acute and subchronic (2 weeks) EFV administration in a series of behavioral tests for anxiety-like and depression-like behavior in healthy rats. We also evaluated the effect of EFV treatment in striatal concentrations of monoamine neurotransmitters (serotonin, dopamine and noradrenaline) and their metabolites and the amino acid neurotransmitters glutamate and GABA. Our results showed that acute treatment with EFV induced an anxiogenic-like effect, while sub-chronic treatment induced both anxiogenic-like and depressive-like behavior which was dose related.. Additionally, EFV treatment caused marked alterations in the striatal concentrations of monoamines and their metabolites (and turnover rates) and the amino acid neurotransmitters glutamate and GABA. These changes were influenced by treatment duration and dose. These findings add more evidence about the neuropsychiatric adverse effects of EFV and propose potential new mechanisms for the toxic action of this drug in the central nervous system.