Inhibition of N-type calcium currents by lamotrigine in rat amygdalar neurones

Lamotrigine (LAG) is a new anticonvulsant drug for the treatment of partial and secondarily generalized seizures. The present study was aimed at elucidating the possible involvement of Ca2+ channels in the action of LAG using whole-cell patch clamp recordings in acutely dissociated amygdalar neurones. Whole-cell Ca2+ currents (ICa) were elicited by 200 ms step commands from -70 mV to -10 mV. Application of LAG reduced the ICa by an average of 40.3 +/- 3.2%. The inhibition of ICa by LAG was markedly reduced or eliminated in the presence of the N-type Ca2+ channel blocker omega-conotoxin-GVIA (1 microM). These results suggest that LAG may exert its anticonvulsant effect through inhibition of presynaptic N-type Ca2+ channels, thereby reducing glutamate release.

The effects of induced apneic episodes on cerebral cortical oxygenation in newborn piglets

The effect of different inspiratory oxygen levels (FiO2) on cortical oxygenation (pO2) during and after recovery from apnea, was investigated in 18 anesthetized, paralyzed, and mechanically ventilated newborn piglets. Heart rate (HR) and mean arterial blood pressure (MABP) were continuously monitored as the piglets were subjected to repeated episodes of apnea initiated by disconnecting the ventilator and terminated when HR decreased to less than 80 beats/min by reconnecting the ventilator. A closed cranial window was placed over the parietal cortex of the animals and cortical pO2 was measured optically by phosphorescence quenching. Apneic episodes induced in animals ventilated with 15%, 22% and 40% oxygen had mean duration's of apnea (time before HR decreased to less than 80 beats/min) of 80, 128 and 134 s, respectively. By the end of the apnea the MABP decreased to 82%, 64%, and 54% of control, respectively. The cortical pO2 decreased from control values of 24.1, 32.3 and 38.3 Torr at 15%, 22% and 40% oxygen, respectively, to 1.7 to 3.2 Torr at the end of the apneic episode. The duration of apnea necessary for the cortical pO2 to drop below 20.3 Torr was 18, 44 and 81 s at 15%, 22% and 40% oxygen, respectively. There was an inverse correlation between the rate of decline of cortical pO2 and baseline FiO2 levels. With reventilation, the cortical pO2 reached maximal values of 42.8, 51.9 and 57.2 Torr at 15%, 22%, and 40% oxygen, respectively, before returning to the pre-apnea values. The present results show that apnea of less than 30 s duration at an FiO2 of 22% do not result in significant cortical hypoxia in hemodynamically stable piglets. Increasing the FiO2 to above 22% may possibly increase the rate of recovery of tissue oxygenation but it also may facilitate post-hypoxic cortical hyperoxia, a factor that may predispose the immature brain to free radical injury.

Peritoneal dialysis-related peritonitis treatment recommendations: 1996 update

The recommendations provided in this document represent a distillation of various experiences, as well as data obtained from published studies in the setting of substantial changes in antibiotic sensitivity. It is hoped that this revised compilation will provide a basis upon which future developments and advances can be made in the therapeutic approach to infectious complications of peritoneal dialysis.

Differences in factors influencing the familial aggregation of febrile convulsion in population and hospital patients

Socio-demographic data, initial clinical manifestations, outcome and family aggregation of febrile convulsion (FC) were compared between 85 population and 364 multicenter patients. More patients presented with clustering of seizures and had recurrence of FC in multicenter group than in population group. Multicenter patients had more fever episodes per year, more day-card attendance and a higher incidence of FC history in their parents. The odds ratio of FC in the siblings was 6:1 in population group and 12:1 in multicenter group. Lower socioeconomic status influenced the presence of FC in the sibling of population group. Instead, FC histories in the father and paternal cousins of probands had influence on the presence of FC in the siblings of multicenter group. We conclude that the population FC sample rather than the hospital sample is the more representative. And there are differences not only in the clinical manifestations but also in the effect of environmental and genetic influences on the family aggregation in population and hospital patients.

L-deprenyl (selegiline) decreases excitatory synaptic transmission in the rat hippocampus via a dopaminergic mechanism

The effect of L-deprenyl (selegiline) on the excitatory synaptic transmission was characterized in the CA1 neurons of rat hippocampal slices by using a intracellular recording technique. Superfusion of L-deprenyl (0.1-10 microM) reversibly decreased the EPSP, which was evoked by orthodromic stimulation of the Schaffer collateral-commissural afferent pathway in a concentration-dependent manner. The sensitivity of postsynaptic neurons to the glutamate receptor agonists, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid or N-methyl-D-aspartate, was not affected by L-deprenyl (1 microM) pretreatment. In addition, L-deprenyl (1 microM) clearly increased the magnitude of paired-pulse facilitation regardless of the interstimulus intervals of 20 to 300 msec used. The ability of L-deprenyl to decrease the EPSP amplitude was not observed in the dopamine-depleted rats. Pargyline and 4-phenylpyridine, the monoamine oxidase type B inhibitors, mimicked the depressant effect of L-deprenyl on the EPSP. Moreover, the reduction of L-deprenyl (1 microM) on the EPSP amplitude was specifically antagonized by sulpiride (0.01-0.1 microM), a selective dopamine D2 receptor antagonist. However, the dopamine D1 receptor antagonist, SKF-83566 (1-10 microM), did not significantly affect L-deprenyl's action. These results indicate that the monoamine oxidase type B inhibitory ability leading to an increase of the dopaminergic tonus in the hippocampus is involved in the L-deprenyl-induced depression of excitatory synaptic transmission in the CA1 region of the rat hippocampus. Moreover, application of L-deprenyl (1 and 10 microM) also reversibly suppressed the epileptiform activity evoked by picrotoxin.

Presynaptic inhibition of excitatory neurotransmission by lamotrigine in the rat amygdalar neurons

Lamotrigine (LAG) is a new antiepileptic drug which is licensed as adjunctive therapy for partial and secondary generalized seizures. In the present study, the mechanisms responsible for its antiepileptic effect were studied in rat amygdaloid slices using intracellular recording and whole-cell patch clamp techniques. Bath application of LAG (50 microM) reversibly suppressed the excitatory postsynaptic potentials (EPSPs) and currents (EPSCs) evoked by stimulating ventral endopyriform nucleus. Synaptic response mediated by the N-methyl-D-aspartate (NMDA) receptor (EPSPNMDA) was isolated pharmacologically by application of a solution containing non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX,10 microM) and gamma-aminobutyric acidA receptor antagonist bicuculline (20 microM). LAG produced a parallel inhibition of EPSPNMDA. Postsynaptic depolarization induced by alpha-amino-5-methyl-4-isoxazole propionate (AMPA) was not altered by LAG. In addition, LAG increased the ratio of the second pulse response to the first pulse response (P2/P1), which is consistent with a presynaptic mode of action. The L-type Ca+2 channel blocker nifedipine (20 microM) had no effect on LAG-induced presynaptic inhibition. However, the depressant effect of LAG was markedly reduced in slices pretreated with N-type Ca+2 channel blocker omega-conotoxin-GVIA (omega-CgTX-GVIA, 1 microM) or a broad spectrum Ca+2 channel blocker omega-conotoxin-MVIIC (omega-CgTX-MVIIC, 1 microM). It is concluded that a reduction in omega-CgTX-GVIA-sensitive Ca+2 currents largely contributes to LAG-induced presynaptic inhibition.

Middle ear catalase distribution in an animal model of otitis media

Increasing evidence implicates free radicals in the pathogenesis of inflammatory disease, including otitis media. The anti-oxidant enzymes catalase, glutathione peroxidase and superoxide dismutase protect tissues from the destructive effects of free radicals. Our previous work has shown depressed levels of superoxide dismutase in the infected middle ears of a guinea pig model of otitis media in comparison with normal control ears. We studied the distribution and relative abundance of catalase in the middle ear of this animal model in an effort to elucidate the role free radicals play in the pathogenesis of otitis media. Catalase distribution was mapped immunohistochemically in the middle ears of guinea pigs with induced streptococcus otitis media, and compared with normal control ears. In the control ears, catalase was localized to the epithelium of the middle ear mucosa, with scant distribution in the submucosa. The infected ears demonstrated inflammatory cell invasion with hyperemia and submucosal edema. Catalase was localized to the epithelium and had scant distribution in the submucosa. This distribution was similar to that found previously with superoxide dismutase. Enzyme-linked immunosorbent assay of catalase demonstrated a mean value of 1.00 +/- 0.06 microgram/mg protein in the control ears, and 1.06 +/- 0.12 microgram/mg in the infected ears, but these two values were not statistically different.

Severe myoclonic epilepsy in infancy: evolution of electroencephalographic and clinical features

Since 1987, we have diagnosed 10 patients, 4 males and 6 females, aged 2-11 years at the last evaluation, who all met the following criteria of severe myoclonic epilepsy in infancy (SMEI): generalized or unilateral long-lasting febrile clonic seizures in the first year of life; the subsequent appearance of myoclonic seizures and other types of seizure (partial seizures, atypical absences and convulsive status epilepticus); and neuropsychological deterioration for a certain period. Family histories of epilepsy and febrile seizures could be traced in 1 and 3 cases, respectively. None of them had previous personal history of brain insult. Electroencephalographic (EEGic) recordings in febrile seizure stage were normal; and continuous prophylaxis with phenobarbital failed to prevent the recurrence of febrile seizures. EEG studies in myoclonic stage showed generalized spike-and-waves, polyspike-and-waves, focal abnormalities and/or photosensitivity. The seizures were highly resistant to antiepileptic drugs. Our experiences suggested that comedication of valproic acid, clonazepam and carbamazepine may be most effective in treatment of the diverse seizures including myoclonic seizures, myoclonic-tonic-clonic seizures, atypical absences and partial seizures. Myoclonic seizures and atypical absences diminished in parallel to a clear-cut decrease in generalized abnormalities on EEG in 4 cases aged more than 7 years. However, the partial seizures, secondarily generalized seizures and status epilepticus were still present. Further investigations should aim to identify the underlying etiology and to search more effective treatment.

Intravenous immunoglobulin therapy in POEMS syndrome: a case report

One course of intravenous immunoglobulin was tried on a patient with the syndrome of polyneuropathy, organomegaly, endocrinopathy, M-protein and skin lesions and Castleman's disease. No effect was noted.

Involvement of the alpha subunit of farnesyl-protein transferase in substrate recognition

Using photoaffinity labeling, we have identified a region in mammalian farnesyl-protein transferase (FPTase) involved in substrate recognition. The photolabel used (Compound 1) is a peptide containing the photoactive amino acid p-benzoylphenylalanine (Bpa). Upon exposure to UV light. Compound 1 inhibits FPTase activity in a time- and concentration-dependent manner. Photoinhibition of FPTase activity by Compound 1 is prevented by adding H-Ras to the reaction mixture, indicating that labeling is targeted to the enzyme active site. We used peptide mapping by HPLC, Edman sequencing, and matrix-assisted time-of-flight (MALDI-TOF) mass spectrometry to identify the site of interaction with radiolabeled Compound 1. These experiments indicate that a specific region of the alpha subunit of the enzyme, Asp110-Arg112, is involved in substrate binding and suggest that Glu111 is likely to be the residue covalently modified by the photoaffinity label. Sequence alignments between yeast and mammalian FPTases reveal that Glu111 is conserved. The implications of this finding are discussed in light of previous mutagenesis studies on FPTase.

Intentional replantation for iatrogenic perforation of the furcation: a case report

Intentional replantation is an accepted endodontic procedure for treatment of teeth in which conventional surgical endodontic treatment is contraindicated. This article presents a rare case of intentional replantation of a mandibular molar that had severe periodontal destruction resulting from iatrogenic perforation of the furcation. A 17-month follow-up evaluation revealed an asymptomatic and functional tooth with no radiographic signs of pathosis. The favorable results obtained might be attributed to the preservation of the vitality of the periodontal ligament; the absence of damaging pressure during extraction; the minimal extraoral treatment time; the use of nonrigid splinting; and the immediate repair of the perforation during a one-visit endodontic procedure. The results obtained with this tooth may indicate the possibility of a successful surgical technique for this otherwise hopeless complication of endodontic therapy.

Mutual inhibitory effects between dopamine and carbachol on the excitatory synaptic transmission in the rat neostriatum

The interactions between dopamine and carbachol on the excitatory synaptic transmission were studied in rat neostriatal slices using an intracellular recording method. Excitatory postsynaptic potentials (EPSPs) were evoked by cortical stimulation. Application of dopamine (DA; 0.1 microM) or carbachol (0.1 microM) produced a dramatic and reversible inhibition of the EPSP amplitude. The inhibitory effect induced by carbachol was markedly attenuated in the presence of either DA (0.1 microM) or the selective D2 dopaminergic receptor agonist (+/-)-2-(N-phenylethyl-N-propyl) amino-5-hydroxytertralin (PPHT; 0.1 microM), but not by the D1 dopaminergic receptor agonist (+/-)-7, 8-dihydroxy-3-allyl-1-phenyl-2, 3, 4, 5-tetrahydro-1H-3-benzazepine (SKF-38393; 0.1 microM) or the D3 dopaminergic receptor agonist R(-)-(4aS, 10bS)-3, 4, 4a, 10b-tetrahydro-4-propyl-2H, 5H-[1] benzogyrano-[4,3-b]-1, 4-oxazin-9-ol (PD-128,907; 0.1 microM). Conversely, muscarinic receptor activation with carbachol (0.1 microM) also completely abolished the DA-induced depression of the EPSP amplitude. In addition, the inhibitory effect of DA on the carbachol-induced depression of the EPSP amplitude was antagonized by sulpiride (1 microM), a selective D2 dopaminergic receptor antagonist. However, D1 dopaminergic receptor antagonist (+/-)-7-bromo-8-hydroxy-3-methyl-1-phenyl-2, 3, 4, 5-tetrahydro-3-benzazepine (SKF-83566; 1 microM) did not affect DA's inhibition. Rp-adenosine-3',5'-cyclic monophosphothioate (Rp-cAMPS; 25 microM), a potent inhibitor of cAMP-dependent protein kinase A (PKA), alone decreased the amplitude of EPSP below baseline values and mimicked the inhibitory effect of DA on the carbachol-induced depression of the EPSP amplitude. Based on these findings, we conclude that the inhibitory effects of D2 dopaminergic receptor and muscarinic receptor activation on the excitatory synaptic transmission in the neostriatum are non-additive and therefore are antagonistic interactions. furthermore, the effect of muscarinic receptor stimulation will depend on the extent of D2 dopaminergic receptor activation and the modulation of the cellular PKA-dependent messenger system seems to contribute to their interactions.

TXA2 agonists inhibit high-voltage-activated calcium channels in rat hippocampal CA1 neurons

Whole cell voltage clamp recordings were used to investigate the effects of thromboxane A2 (TXA2) agonists on the voltage-dependent Ca2+ currents in rat hippocampal CA1 neurons. TXA2 agonists [1S-[1 alpha, 2 beta(5Z), 3 alpha(1E, 3S*)4 alpha ]]-7-[3-[3-hydroxy-4-(4'-iodophenoxy)-1-butenyl]-7-oxabicyclo [2,2,1]heptan-2-yl]-5-heptenoic acid (I-BOP) and U-46619, reversibly suppressed the whole cell Ca2+ currents in a concentration-dependent manner. The effect was blocked by specific TXA2 receptor antagonist, SQ-29548. I-BOP as well as U-46619 inhibited both omega-conotoxin GVIA (CgTx)-sensitive and nimodipine sensitive Ca2+ currents but had no effect on CgTx/nimodipine insensitive Ca2+ currents. The I-BOP and U-46619 inhibition of Ca2+ currents was blocked by internal dialysis of hippocampal neurons with specific protein kinase C (PKC) inhibitors, NPC-15437 and PKC inhibitor-(19-36). Pretreatment of hippocampal neurons with either 5 micrograms/ml pertussis toxin (PTX) or 5 micrograms/ml cholera toxin (CTX) did not significantly affect the suppression of the Ca2+ currents by I-BOP and U-46619. Dialyzing with 1 mM guanosine 5'-O-(3-thiotriphosphate) or 1 mM GDP significantly attenuated the I-BOP or U-46619 action. These results demonstrate that TXA2 agonists inhibit both CgTx- and nimodipine-sensitive Ca2+ currents but not CgTx/nimodipine-insensitive currents in rat hippocampal CA1 neurons via a PTX- and CTX-insensitive G protein-coupled activation of the PKC pathway.

Carbon disulfide induced polyneuropathy: sural nerve pathology, electrophysiology, and clinical correlation

We report the clinical features, electrophysiological studies, sural nerve pathology and recovery course of carbon disulfide-(CS2) induced polyneuropathy in a 48-year-old man who worked in a viscose rayon plant. Sural nerve biopsy 2 years later still showed degeneration of both axon and myelin with a predominant loss of large myelinated fibers and remyelination. Electrophysiologic studies revealed mixed axonal and demyelinating polyneuropathy. To our knowledge, this is the first human report of sural nerve pathology in the recovery stage due to CS2 intoxication. After diagnosis, the patient was removed from the toxic environment. In the following three years, he showed part recovery predominantly in motor function compatible with the serial nerve conduction studies. We conclude that CS2 polyneuropathy may partly recover years after cessation of exposure.

Structural motifs encoded by individual exons of the human neurokinin-1 receptor gene interact differentially with selective agonists and antagonists

Three chimeric receptors were constructed by exchanging exons between human neurokinin NK1 and NK3 receptor genes. The N-terminal sequences of these chimeric receptors are encoded by exon 1, exon 1-2, or exon 1-3 of the NK1 receptor gene, whereas the remaining C-terminal sequences of these chimeric receptors are encoded by corresponding exons of the human NK3 receptor gene. Substance P bound with high affinities to all three chimeric receptors, suggesting that in addition to the common structures composed of conserved amino acid residues among neurokinin receptors, structural elements encoded by the first exon of the human NK1 receptor gene may also play an important role for substance P binding. On the contrary, potent NK1 antagonists L703,606 and SR140,333 did not show any detectable binding to these chimeric receptors. In accordance, sequences encoded by exon 4, and possibly exon 5, are likely to contain important structural motifs that may directly or indirectly influence the binding of these antagonists. Further comparison of the binding affinities of highly selective NK1 agonists, [Sar9, Met(O2)11] substance P, substance P methyl ester, and septide, revealed that each agonist may interact differently with the human NK1 receptor. These results show that the exon-exchanging technique can be a useful tool for studying structure-function relationships of receptors in which exon-intron junctions are fully conserved among receptor subtypes.

Second trimester diagnosis of thanatophoric dysplasia

Thanatophoric dysplasia is one of the most common skeletal dysplasia, with an incidence from 1:6,400 to 1:100,000 births. While the etiology is unknown, either autosomal recessive or polygenic transmission with 0.2% recurrence risk had been suggested. It is a lethal disorder characterized by extremely short ribs, tubular bones and macrocephaly. Death is often secondary to pulmonary hypoplasia caused by the small thoracic cavity. We present a fetus with shortening of four limbs, typical thanatophoric dwarfism, diagnosed by sonography at the 25th week of gestation. The second trimester diagnosis by ultrasound was crucial, because it gave an alternative option of pregnancy termination when the affected fetus was discovered.

Mediation of signal transduction in keratinocytes of human middle ear cholesteatoma by ras protein

Immunolocalization was used to investigate the distribution of ras protein in both congenital and acquired cholesteatoma tissues. A pathological feature of middle ear cholesteatoma included accumulation of keratin debris due to active proliferation and differentiation of keratinocytes. Ras protein localized to the inner plasma membrane and cytoplasm of keratinocytes in all of the epithelial layers in both congenital and acquired cholesteatoma specimens. Keratinocytes in the basal layer were stained more intensely than their differentiated counterparts. Findings also demonstrated that receptors for epidermal growth factor, fibroblast growth factor, and plateletderived growth factor were present in the plasma membrane of keratinocytes. C-jun, a transcription factor was found in the nuclei of keratinocytes of the cholesteatoma epithelium. These findings indicate that ras protein plays a pivotal role in a signal transduction cascade between growth factor receptors in the plasma membrane and the transcription factor, c-jun, in the nuclei of keratinocytes during the growth of cholesteatoma.

Post-renal transplant erythrocytosis

Erythrocytosis is a relatively common phenomenon following renal transplantation. It is not only associated with some special clinical conditions, but also increases the risk of thromboembolism. We therefore studied the clinical manifestations and possible risk factors of erythrocytosis in our renal-transplant patients. Study of 175 patients showed that erythrocytosis, defined as Hct > or = 50%, was found in 17 patients (9.7%), 14 males and 3 females. Among these 17 patients, 13 received cadaveric grafts and the other 4 living-related grafts. True erythrocytosis, defined as erythrocytosis with elevated red blood cell (RBC) mass, was found in 7 patients. Relative erythrocytosis, defined as erythrocytosis with normal RBC mass, was found in the other 10 patients. Six patients developed acquired renal cysts of the native or graft kidneys during the post transplant period. The incidence of acquired renal cysts in the erythrocytosis group was significantly higher than that in the non-erythrocytosis group. The clinical and demographic characteristics were similar in terms of age, gender, serum albumin, and serum creatinine in the erythrocytosis and non-erythrocytosis groups. The incidences of abnormal liver function, and hypertension were similar between the 2 groups. Seventeen of the 161 patients (10.6%) receiving cyclosporine regimen developed erythrocytosis, but none of the 14 patients receiving non-cyclosporine regimen developed erythrocytosis (p > 0.05). Only one patient with true erythrocytosis had an elevated serum erythropoietin (EPO) level and no thromboembolic complications occurred in the erythrocytosis group. We conclude that: (1) the incidence of erythrocytosis in our transplant patients was 9.7%; (2) a higher incidence of acquired renal cysts was found in the erythrocytosis group; (3) most of the patients with erythrocytosis had a normal serum EPO level; (4) no thromboembolic complications occurred in our patients.

Blockade of isoproterenol-induced synaptic potentiation by tetra-9-aminoacridine in the rat amygdala

The effects of tetrahydro-9-aminoacridine (THA) on beta-adrenoceptor activation-induced synaptic potentiation were studied in brain slices of the rat amygdala using intracellular recording techniques. To exclude the involvement of N-methyl-D-aspartate (NMDA) receptors, all the experiments were performed in the presence of NMDA receptor antagonist, D-APV (50 microM). Bath application of isoproterenol (Iso; 15 microM) results in a long-lasting enhancement of the amplitude of excitatory postsynaptic potentials (EPSPs) to 200 +/- 6% of baseline. Forskolin, which directly activates adenyl cyclase, produces a similar effect suggesting that Iso may act through a cyclic AMP-dependent mechanism. Pretreatment of the slices with THA (300 microM) completely abolishes the Iso- and forskolin-induced synaptic potentiation. We hypothesize that the locus of THA/beta-adrenoceptor interaction is presynaptic; the underlying mechanism is likely due to THA's depression of transmitter release via a presynaptic blockade of voltage-dependent Ca2+ channels.

Carbachol induces inward current in neostriatal neurons through M1-like muscarinic receptors

The effects of carbachol on rat neostriatal neurons were examined in the slice and the freshly dissociated neuron preparations using intracellular and whole-cell voltage-clamp recording methods. Superfusion of carbachol (30 microM) produced a depolarization concomitant with an increase in the rate of spontaneous action potentials. This depolarization was associated with an increase in the input resistance. The carbachol-induced membrane depolarization was blocked by pirenzepine (1 microM), a selective M1 muscarinic receptor antagonist. In other experiments, we observed that carbachol induced a transient inward current on the freshly dissociated neostriatal neuron at a holding potential of -60 mV in a concentration-dependent manner underlying the whole-cell voltage-clamp mode. The inward current caused by carbachol was not reduced by tetrodotoxin (1 microM), calcium-free recording solution or Cd2+ (100 microM). However, it was blocked by Ba2+ (100 microM). In addition, the carbachol-induced inward current reversed polarity at about the potassium equilibrium potential. The whole-cell membrane inward current in response to voltage-clamp step from -90 to -140 mV was reduced by 30 microM carbachol. With stronger hyperpolarization beyond the potassium equilibrium potential, carbachol produced a progressively greater reduction in membrane current. This inhibitory effect was also abolished by Ba2+ (100 microM). A concentration of 30 microM carbachol-induced inward current could be reversibly antagonized by the M1 muscarinic receptor antagonist pirenzepine (0.1-1 microM), with an estimated IC50 of 0.3 microM. However, other muscarinic receptor subtype (M2 or M3) antagonists could also block the carbachol-induced inward current. The rank order of antagonist potency was: pirenzepine (M1 antagonist) > 4-diphenylacetoxy-N,N-methyl-piperidine methiodide (M3/M1 antagonist) > gallamine (M2 antagonist). Based on these pharmacological data, we concluded that carbachol can act at M1-like muscarinic receptors to reduce the membrane K+ conductances and excite the neostriatal neurons.