Brazilian Journal of Medical and Biological Research (2003) 36: 239-245 Nitrergic modulation of nigrostriatal transmission 239 ISSN 0100-879X Gender-related differences in the effects of nitric oxide donors on neuroleptic-induced catalepsy in mice J.G.P. Pires, P.G. Costa, Departamento de Ciências Fisiológicas, Centro Biomédico, F.P. Saraiva, V. Bonikovski Universidade Federal do Espírito Santo, Vitória, ES, Brasil and H.A. Futuro Neto Abstract Correspondence It has been suggested that nigrostriatal dopaminergic transmission is Key words J.G.P. Pires modulated by nitric oxide (NO). Since there is evidence that gonadal S Neuroleptic-induced Centro Biomédico, UFES hormones can affect extrapyramidal motor behavior in mammals, we catalepsy Av. Marechal Campos, 1468 investigated the effects of isosorbide dinitrate (ISD), linsidomine S Nitric oxide donors 29042-755 Vitória, ES (SIN-1) and S-nitroso-N-acetylpenicillamine (SNAP), three pharma- S Gender differences Brasil S cologically different NO donors, on neuroleptic-induced catalepsy in Linsidomine Fax: +55-27-3335-7330 S 60- to 80-day-old male and female albino mice. Catalepsy was in- SNAP E-mail: [email protected] S Isosorbide dinitrate duced with haloperidol (1 mg/kg, ip) and measured at 30-min intervals Research partially supported by by means of a bar test. Drugs (or appropriate vehicle) were injected ip FINEP, PRPPG-UFES and FCAA. 30 min before haloperidol, with each animal being used only once. P.G. Costa and F.P. Saraiva were ISD (5, 20 and 50 mg/kg) caused a dose-dependent inhibition of medical students receiving catalepsy in male mice (maximal effect 120 min after haloperidol: PIBIC-CNPq studentships. V. Bonikovski was the recipient 64% inhibition). In the females only at the highest dose of ISD was an of a M.Sc. scholarship from CAPES. attenuation of catalepsy observed, which was mild and short lasting. H.A. Futuro Neto is the recipient SIN-1 (10 and 50 mg/kg) did not significantly affect catalepsy in of a CNPq Productivity Fellowship female mice, while a significant attenuation was observed in males at (No. 520109196-1). the dose of 50 mg/kg (maximal inhibition: 60%). SNAP (20 mg/kg) significantly attenuated catalepsy in males 120 min after haloperidol (44% inhibition), but had no significant effect on females. These results basically agree with literature data showing that NO facilitates Received May 28, 2002 Accepted November 11, 2002 central dopaminergic transmission, although the mechanisms are not fully understood. They also reveal the existence of gender-related differences in this nitrergic modulation in mice, with females being less affected than males. Introduction dopaminergic function and its modulation by other transmitter systems (1-4). Antipsychotic drugs like haloperidol and Nitric oxide (NO) is recognized as a mes- chlorpromazine (the so-called typical neuro- senger molecule in the nervous system, where leptics) induce abnormal motor behaviors in it is synthesized from L-arginine by a nitric experimental animals and humans, includ- oxide synthase (NOS) (5,6). Experimental ing catalepsy in rats and mice (1). Neurolep- evidence suggests that central dopaminergic tic-induced catalepsy in rodents is a robust transmission is affected by NO (7,8). This behavioral method for studying nigrostriatal influence is rather complex, since it can in- Braz J Med Biol Res 36(2) 2003 240 J.G.P. Pires et al. volve either dopamine release, uptake or obtained from our breeding stock. Animals, metabolism (9). Some studies suggest that separated by sex, were housed two per cage endogenous NO increases dopamine release (20 x 18 x 13 cm high) with free access to in the striatum and other areas of the CNS standard pellet food and filtered water, at 23- (10-12), while other authors suggest the op- 26ºC. All observations were made between posite (13,14). If NO increases the release of 9:00 and 17:00 h in a quiet room, with each dopamine in the striatum, we would expect animal used only once. Female mice were that drugs that release or are metabolized tested without monitoring the estrous cycle, into NO (i.e., NO donors) are able to attenu- since the major interest of this study was to ate neuroleptic-induced catalepsy, which is investigate the possibility of NO donors differ- mainly caused by blockade of striatal dopa- entially affecting male and female animals. minergic receptors (1). Consistent with this hypothesis, Krzascik and Kostowski (15) Drug administrations showed that molsidomine, a pro-drug of the NO donor linsidomine (SIN-1), attenuated The drugs used were haloperidol (Hal- haloperidol-induced catalepsy in male rats, dol®, Janssen, São Paulo, SP, Brazil), ISD while we have shown that another NO do- (Sigma, St. Louis, MO, USA; molecular nor, isosorbide dinitrate (ISD), did the same weight = 236.1), SIN-1 hydrochloride (RBI, in male mice (16). Natick, MA, USA; molecular weight = There is a large body of evidence show- 206.63), and SNAP (Tockris Cookson Inc., ing sexual dimorphisms with regard to some Ballwin, MO, USA; molecular weight = aspects of the extrapyramidal motor system, 220.25). Haloperidol was diluted with saline both in humans and in experimental animals (0.9% NaCl). SIN-1 was dissolved by soni- (17,18). In addition, gender-related differ- cation in saline, ISD was dissolved by soni- ences are a common feature of the pharma- cation in a 5% solution (v/v) of ethanol in cological properties of most centrally active saline, and SNAP was dissolved in a 20% drugs (19-21); for instance, drug-induced solution (v/v) of DMSO in saline. The drugs parkinsonism in humans exhibits a female- were freshly prepared and solutions were to-male predominance ratio of about 2:1 (22). protected from light. Nevertheless, there is no information con- The NO donors were injected ip with a cerning gender dimorphism in the effects of 27.5 G needle, in a volume of 6 ml/kg body nitrergic agents on the phenomenon of neu- weight, 30 min before haloperidol. The doses roleptic-induced catalepsy. used were ISD: 5, 20 and 50 mg/kg; SIN-1: The present study was designed to inves- 10 and 50 mg/kg; SNAP: 20 mg/kg. When- tigate the effects of three centrally active NO ever possible, the doses were chosen accord- donors, ISD, SIN-1 and S-nitroso-N-acetyl- ing to those commonly used in the literature. penicillamine (SNAP), on neuroleptic-in- For each experimental group, appropriate duced catalepsy in male and female mice. vehicle (6 ml/kg, ip) was used as control. Preliminary accounts of these observations were published in abstract form (23,24). Procedure Material and Methods Catalepsy was induced with haloperidol (1 mg/kg, ip) and determined at 30-min in- Animals tervals by means of a standard bar test (3,16). This dose of haloperidol was chosen to pro- Experiments were performed on 60- to duce a moderate degree of catalepsy so that 80-day-old albino mice weighing 26-36 g, inhibition or potentiation of catalepsy could Braz J Med Biol Res 36(2) 2003 Nitrergic modulation of nigrostriatal transmission 241 be detected (1,16). The phenomenon was Effects of linsidomine on neuroleptic-induced measured as the time the animal maintained catalepsy an imposed position with both front limbs extended and resting on a 3-cm high wood In contrast to male mice, in which the bar (0.9 cm in diameter). The end point of higher dose of SIN-1 significantly inhibited catalepsy was considered to occur when both neuroleptic-induced catalepsy by about 60% front paws were removed from the bar or if (Figure 2A), the NO donor did not signifi- the animal moved its head in an exploratory cantly modify the duration of catalepsy in manner. A cut-off time of 720 s was used. the females (Figure 2B). In six separate male The animals were returned to their home mice (data not shown), which received 10 cages between determinations. mg/kg SIN-1 at 110 min after haloperidol (instead of 30 min before), the NO donor Statistical analysis caused a short-lasting but statistically sig- nificant attenuation of catalepsy. Data are reported as means ± SEM for 10 mice per group. For statistical purposes, Effects of SNAP on neuroleptic-induced the durations of catalepsy were transformed catalepsy to logarithmic (ln x+1) values in order to normalize the data. Significant differences Pretreatment of male mice with SNAP were initially assessed by two-way ANOVA (20 mg/kg) caused a short-lasting but statis- with repeated measures (treatment and time tically significant inhibition (about 44%) of as factors); if significance was detected for treatment x time interactions, one-way Figure 1. Effects of isosorbide 200 dinitrate (ISD) on neuroleptic-in- ANOVA with repeated measures followed by A duced catalepsy in male (A) and the two-tailed Dunnett test was performed for female (B) mice. ISD, or appro- each time point to determine differences be- 150 priate vehicle as control, was in- jected ip 30 min before haloperi- tween control and other experimental groups. dol (1 mg/kg, ip). Data are re- The level of significance was set at P<0.05. ported as means ± SEM, N = 10 100 ** mice per group. Filled circles, ** vehicle; triangles, 5 mg/kg ISD; Results ** squares, 20 mg/kg ISD; open 50 ** Duration of catalepsy (s) * circles, 50 mg/kg ISD. *P<0.05 * Effects of isosorbide dinitrate on * compared to vehicle (Dunnett test). 0 neuroleptic-induced catalepsy 30 60 90 120 150 180 Time after haloperidol (min) ISD (5-50 mg/kg) caused a dose-depend- ent attenuation of neuroleptic-induced cata- 300 B lepsy in male mice (Figure 1A). The maxi- 250 mal effect obtained was 64% inhibition, ob- served at 120 min after haloperidol.