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PubMed1997

Development of a radioimmunoassay for Cebus apella prolactin.

Prolactin (PRL) is a pituitary hormone that plays important roles in mammalian reproductive physiology, specially lactation. The regulation of PRL secretion shows important species differences. To study PRL regulation in a subhuman primate, the Cebus apella, we developed an heterologous radioimmunoassay using an antibody against rhesus PRL (anti-m5PRL) and a Cebus apella pituitary extract as PRL standard. The assay has a sensitivity that allows measurements of cebus PRL in small amounts of Cebus apella plasma obtained from animals in different physiological conditions. Plasma cebus PRL concentrations (+/-SEM) varied in different reproductive stages. PRL concentration in adult Cebus apella females that have regular menstrual cycles (161.6 +/- 15.0 mIU/ml) was similar to that found in adult (100.3 +/- 7.6 mIU/ml) and prepuberal males (101.2 +/- 3.9 mIU/ml). PRL concentration was higher in pregnant (677.8 +/- 11.8 mIU/ml) and in nursing (625.0 +/- 47.0 mIU/ml) Cebus apella females than in 15-d post-partum non-nursing (369.0 +/- 19.0 mIU/ml) and cycling females. PRL concentration in Cebus apella newborns (719.0 +/- 49.2 mIU/ ml) was similar to that found in pregnant and nursing females, and higher than in the other females as well as adult and prepuberal males. These differences in PRL concentration in different physiological conditions are similar to that observed in humans and other primates. A PRL response to thyrotropin releasing hormone (TRH) was demonstrated in 2 nursing Cebus apella females, similar to the response found in nursing woman and rhesus. Altogether, the data presented support the proposal that the assay developed to measure PRL in Cebus apella is an adequate tool to study the physiology of PRL in this species.

Animals↗
PubMed1999

Model for the fetal recruitment of simian gamma-globin genes based on findings from two New World monkeys Cebus apella and Callithrix jacchus (Platyrrhini, Primates).

The originally embryonic gamma-globin locus duplicated and acquired a novel (fetal) pattern of expression in a defined time period (55-40 million years ago) during primate phylogeny. The objective of this study was to determine some of the factors that led to first the emergence of fetal gamma specificity and then the maintenance of different fetal gamma expression patterns in extant simian primates (e.g., human, capuchin monkey). Analyses focused on two platyrrhine (New World monkey) species: the common marmoset (Callithrix jacchus) and the brown capuchin monkey (Cebus apella), each of which has paired, non-allelic gamma loci (5'-gamma 1-gamma 2-3'). Quantitation of beta-type globin mRNAs expressed in a 4.5 week old embryo of Callithrix jacchus revealed that in addition to its primary epsilon-globin message, considerable amounts of gamma 1 message and just trace levels of gamma 2 message are present. In contrast, analyses of gamma-globin messenger RNAs expressed in a Cebus apella fetal liver indicated that gamma 2 expression is at least 120 times greater than gamma 1 expression. Using a luciferase reporter and a transient assay system, the strengths of gamma 1 and gamma 2 promoter fragments of Cebus apella were compared in erythroid (K562) and non-erythroid (HeLa) cell lines. Due to the lack of chromatin repression in a transient expression system, the results do not fully recapitulate globin expression. However, the results suggest that sequences contained within the Cebus gamma 1 and gamma 2 proximal promoter regions (-200 to +1 bp) can direct gamma transcription in both cell lines. In K562 and, to a lesser extent, in HeLa cells Cebus gamma 2 promoter fragments were significantly stronger (P < 0.01) than gamma 1 promoter fragments. This is consistent with the fact that the Cebus gamma 1 promoter contains several mutations, including a proximal CCAAT box mutation (CCAAT-->CCAAc). The epsilon-gamma 1 intergenic distances in these platyrrhines (5.4 kb in Cebus apella and 6.9 kb in Callithrix jacchus) are short, supporting the inference that it was also short in the stem simian primates. The results suggest that immediately following the gamma duplication, the gamma 1 gene of the stem simians was still embryonic and the downstream gamma 2 gene was largely silent. A further inference is that once gamma 2 accumulated regulatory mutations that disrupted binding of fetal repressors, gamma 2 was expressed fetally and, through gene conversion, passed these characteristics to the gamma 1 gene. The fetal expression of gamma 1 is most evident in catarrhines (Old World monkeys and hominoids), which preferentially express the gamma 1 locus during fetal life.

Animals↗
PubMed1985

Molar microwear and diet in the genus Cebus.

Recent analyses have documented differences in dental microwear between primate species with different diets, especially between primate hard-object feeders and primate leaf-eaters. Thus far, these microwear differences have only been documented for primates with vastly different foraging strategies and geographic distributions. To see if similar differences could be documented for closely related species, dental replicas from Cebus apella, Cebus nigrivittatus, and Cebus capucinus were examined using scanning electron microscopy. Quantitative analyses reveal that (1) even for closely related species, microwear differences between facets of one species are still far less than those between homologous facets of different species; and (2) the dental microwear of Cebus apella, Cebus nigrivittatus, and Cebus capucinus are still significantly different from one another. Furthermore, the data suggest that the dietary differences between these species may center around the presence or absence of hard objects in the diet.

Animals↗
PubMedDate not supplied

Aortic intimal response to endothelial removal in cebus and squirrel monkeys.

Whereas squirrel monkeys have an inherent susceptibility to atherosclerosis, cebus monkeys are relatively resistant. To assess whether this difference might lie in their response to endothelial injury, the acute morphologic changes in the aortic intima after endothelial removal were examined in the two species. The endothelium of the lower thoracic aorta was removed with an embolectomy catheter, and the intimal response was compared with the uninjured upper thoracic aorta in each monkey. By 21 days after aortic denudation, regrowth of the endothelium (assessed by in vivo Evans' blue dye staining) was significantly greater in squirrel monkeys (90% +/- 5% of aortic surface) than in cebus (56% +/- 11%). Squirrel monkeys had comparable sudanophilic surface in the nonballooned, control aorta (25% +/- 7%) and the ballooned, lower thoracic segment (17% +/- 6%). Cebus monkey aortas had no sudanophilia in either segment. The intima/media ratios (IMR) in all regions of the aorta were significantly greater in squirrel monkeys than in cebus, but in both species the IMR of the ventral ballooned segment was two to three times the IMR of the nonballooned control segment. In the dorsal aorta, where endothelial regrowth was more rapid, the IMR was similar to the control aortic segment. By electron microscopy the thickened aortic intima in both species contained a marked increase in modified smooth muscle cells, but lipid accumulation did not result from endothelial removal or regrowth in either species. Thus, although the squirrel monkey aorta had atherosclerotic lesions before endothelial removal, the acute intimal response to endothelial injury was similar in degree and kind in both cebus and squirrel monkeys. This suggests that factors other than those controlling the initial intimal thickening following endothelial injury are responsible for the observed difference in arterial lipid accumulation between cebus and squirrel monkeys.

Animals↗
PubMed1985

Dietary fat unsaturation enhances drug metabolism in cebus but not in squirrel monkeys.

Antipyrine disappearance and sleeping time following barbiturate anesthesia were assessed to evaluate the effects of dietary corn oil and coconut oil on the drug-metabolizing enzyme systems (DMES) in cebus (Cebus albifrons) and squirrel (Saimiri sciureus) monkeys. Plasma antipyrine clearance (half-life) was measured in both species before and after induction of DMES by i.v. injection of barbiturates on two consecutive days. Sleeping time was measured after administration of either pentobarbital or hexobarbital and proved to be the most demonstrable measure of diet-drug interaction. In neither cebus nor squirrel monkeys was antipyrine half-life significantly affected by dietary fat. Sleeping time for the coconut oil-fed squirrel monkeys was shorter than for those fed corn oil, whereas corn oil-fed cebus awoke sooner than the coconut oil-fed cebus. Thus, barbiturate but not antipyrine metabolism in monkeys can be influenced by dietary fat unsaturation, and the effect appears to be species dependent. Genetic differences in phospholipid metabolism are thought to underlie this difference.

Animals↗
PubMed1994

Tactile discrimination capacity in relation to size and organization of somatic sensory cortex in primates: I. Old-World prosimian, Galago; II. New-World anthropoids, Saimiri and Cebus.

Living primates vary considerably in brain organization, in sensorimotor and cognitive abilities, and in natural behavioral repertoires. Comparative studies of primary (SI) and secondary (SII) somatic sensory cortex of primates reveal major differences in the size and in the complexity of topographic projection patterns. The separate projections of the glabrous hand to SI cytoarchitectonic areas 3b and 1 described in the Old World (OW) anthropoid Macaca and in New World (NW) anthropoids Cebus, Saimiri, and Aotus are lacking in NW Saguinus and in the prosimian Galago. The relationship between the size and complexity of SI organization and tactile abilities is explored in this study of four species of primates--Galago, Macaca, Cebus, and Saimiri. These species were trained to discriminate between pairs of objects differing either in cross-sectional diameter (size) or surface roughness (texture). The course of acquisition of such tactile discrimination in normal Macaca and the nature of deficits following SI or SII removals are known. Selective lesions of either cytoarchitectonic area 1 or 2 in Macaca affect only texture or size discriminations, respectively. Removal of area 3b in SI, or of SII, in Macaca affects both size and texture capacities. The single projection of the glabrous hand to area 3b-1 of Galago led to our expectation that the capacity of Galago to discriminate textures would be more similar to an area 1-lesioned than to a normal Macaca. The substantial and persistent differences between Macaca and Galago on texture, but not size, tasks lend support to the view that the evolution of a second projection of the glabrous hand to area 1 in Macaca contributes to increased texture discrimination capacity. The similarity in multiple projection patterns of the glabrous hand to areas 3b and 1 in Macaca, Saimiri, and Cebus led us to expect greater correspondence in texture discrimination capacity between these three anthropoids than to Galago. Contrary to expectations, Saimiri and Cebus showed a tactile capacity more similar to Galago than to Macaca. Furthermore, the texture discrimination capacity of Cebus actually improved substantially after removal of area 1. This provides further evidence, together with the single SI hand area in NW Saguinus and Galago, that the separate cutaneous projections to area 1 in OW and NW primates are not homologous but evolved independently and possibly serve different tactile functions.

Animals↗
PubMed1977

Relative maturity of cebus and squirrel monkeys at birth and during infancy.

Cebus monkey were less mature at birth than squirrel monkeys in terms of body weight and brain weight in proportion to adult weight. Postnatally, cebus were slower to develop locomotion, perceptual-motor capacities, and object permanence. The differences in rate of development between the species increased with age. The findings indicate that the cebus have a longer period of infancy before becoming skilled at locomotion and manipulation. In view of the cebus monkey's recognized skill as a manipulator and problem solver, the long period of infancy suggests that cebus have evolved further in the direction of higher primates.

Animals↗
PubMed2002

Chromosomal homologies between Cebus and Ateles (primates) based on ZOO-FISH and G-banding comparisons.

ZOO-FISH (Fluorescent "in vitro" hybridization) was used to establish the chromosomal homology between humans (HSA) and Cebus nigrivitatus (CNI) and Ateles belzebuth hybridus (ABH). These two species belong to different New World monkey families (Cebidae and Atelidae, respectively) which differ greatly in chromosome number and in chromosome morphology. The molecular results were followed by a detailed banding analysis. The ancestral karyotype of Cebus was then determined by a comparison of in situ hybridization results, as well as chromosomal morphology and banding in other Platyrrhini species. The karyotypes of the four species belonging to the genus Cebus differ from each other by three inversions and one fusion as well as in the location and amounts of heterochromatin. Results obtained by ZOO-FISH in ABH are in general agreement with previous gene-mapping and in situ hybridization data in Ateles, which show that spider monkeys have highly derived genomes. The chromosomal rearrangements detected between HSA and ABH on a band-to-band basis were 27 fusions/fissions, 12 centromeric shifts, and six pericentric inversions. The ancestral karyotype of Cebus was then compared with that of Ateles. The rearrangements detected were 20 fusions/fissions, nine centromeric shifts, and five inversions. Atelidae species are linked by a fragmentation of chromosome 4 into three segments forming an association of 4/15, while Ateles species are linked by 13 derived associations. The results also helped clarify the content of the ancestral platyrrhine karyotype and the mode of chromosomal evolution in these primates. In particular, associations 2/16 and 5/7 should be included in the ancestral karyotype of New World monkeys.

Animals↗
PubMed1987

Anatomical demonstration of ocular segregation in the retinogeniculocortical pathway of the New World capuchin monkey (Cebus apella).

We describe the architecture of the dorsal lateral geniculate nucleus and primary visual cortex (striate cortex; area 17) of the New World capuchin monkey (Cebus apella) on the basis of the distribution of cell bodies and cytochrome oxidase histochemistry. Changes in staining for cytochrome oxidase following unilateral enucleation served to indicate the organization of the representation of the two eyes in the retinogeniculocortical pathway. The number and disposition of eye-specific layers within the lateral geniculate nucleus of Cebus are consistent with the common plan of geniculate organization in anthropoid primates, and the radial organization of area 17 fits the pattern common to New World squirrel and Old World macaque monkeys, including the presence of cytochrome-oxidase-rich zones in supragranular and deeper cortical layers (Horton: Philos. Trans. R. Soc. Lond. [Biol.] 304:199-253, '84). Our principal finding is that cytochrome oxidase histochemistry following unilateral eye removal unequivocally reveals ocular dominance columns in the striate cortex of Cebus. As in the macaque (Hubel: Nature 292:762-764, '82), ocular dominance columns extend through the thickness of cortex and blobs are centered on columns, but the array of columns viewed tangentially is less orderly or more mosaic than in the macaque, and there is apparently significant overlap between columns. The presence of well-defined ocular dominance columns in Cebus, as in Ateles (Florence, Conley, and Casagrande: J. Comp. Neurol. 243:234-248, '86) but not in other New World monkeys examined previously, emphasizes the phylogenetic lability of binocular segregation in the primate visual cortex. In addition, the present results indicate significant differences with respect to the tangential organization of the ocular dominance domain between primate species in which ocular dominance columns are present.

Animals↗
PubMed1995

DNA evidence on the phylogenetic systematics of New World monkeys: support for the sister-grouping of Cebus and Saimiri from two unlinked nuclear genes.

Previous inferences from epsilon-globin gene sequences on cladistic relationships among the 16 extant genera of Ceboidea (the New World monkeys) were tested by strength of grouping and bootstrap values for the clades in the most parsimonious trees found: for this epsilon data set enlarged with additional Cebus and Saimiri orthologues; for another nuclear DNA sequence data set consisting of IRBP (interstitial retinol-binding protein gene) intron 1 orthologues; and for tandemly combined epsilon and IRBP sequences. Different ceboid species of the same genus always grouped strongly together as demonstrated by results on Cebus (capuchin monkeys), Saimiri (squirrel monkeys), Callicebus (titi monkeys), Aotus (night monkeys), Ateles (spider monkeys), and Alouatta (howler monkeys). Other strong groupings that could be represented as monophyletic taxa in a cladistic classification were: Cebuella (pygmy marmoset) and Callithrix (marmoset) into subtribe Callitrichina; Callitrichina, Callimico (Goeldi's monkey), Leontopithecus (lion tamarin), and Saguinus (tamarin) into subfamily Callitrichinae; Callitrichinae, Aotus, Cebus, and Saimiri into family Cebidae; Cacajao (uakari monkey) and Chiropotes (saki) into subtribe Chiropotina; Chiropotina and Pithecia (bearded saki) into tribe Pitheciini; Pitheciini and Callicebus into subfamily Pitheciinae; Brachyteles (woolly spider monkey), Lagothrix (woolly monkey), and Ateles into tribe Atelini; and Atelini and Alouatta into subfamily Atelinae. In addition the epsilon and IRBP results congruently grouped (but at lesser strengths) Brachyteles and Lagothrix into subtribe Brachytelina within Atelini, and also Cebus and Saimiri into subfamily Cebinae within Cebidae. Because the IRBP results weakly grouped Pitheciinae with Cebidae, whereas the epsilon results weakly grouped Pitheciinae with Atelinae, the present evidence is best represented in an interim cladistic classification of ceboids by dividing the superfamily Ceboidea into three families: Atelidae, Pitheciidae, and Cebidae.

Alouatta↗
PubMed1983

Representations of the body surface in areas 3b and 1 of postcentral parietal cortex of Cebus monkeys.

The somatotopic organization of postcentral parietal cortex was determined with microelectrode mapping methods in a New World monkey, Cebus albifrons. As in previous studies in macaque, squirrel and owl monkeys, two separate representations of the body surface were found in regions corresponding to the architectonic fields 3b and 1. The two representations were roughly mirror-images of each other, with receptive field locations matched for recording sites along the common border. As in other monkeys, the glabrous digit tips of the hand and foot pointed rostrally in the Area 3b representation and caudally in the Area 1 representation. Both representations proceeded in parallel from the tail on the medial wall of the cerebral hemisphere to the teeth and tongue in lateral cortex along the Sylvian fissure. Compared with the other monkeys, the tail of the cebus monkey, which is prehensile, was represented in a very large region of cortex in Areas 3b and 1. Like its close relative, the squirrel monkey, the representation of the trunk and parts of the limbs were reversed in orientation in both Area 3b and Area 1 in cebus monkeys as compared to owl and macaque monkeys. The reversals of organization for some but not all parts of the representations in cebus and squirrel monkeys suggest that one line of New World monkeys acquired a unique but functionally adequate pattern of somatotopic organization for the two adjoining fields.

Animals↗
PubMed1986

Vascular responses of platelet-activating factor in the Cebus apella primate and inhibitory profiles of antagonists SRI 63-072 and SRI 63-119.

We have evaluated several effects of intravenous administration of synthetic platelet-activating factor (PAF) in the non-human primate Cebus apella. Parameters measured were hemoconcentration (monitored by changes in hematocrit), thrombocytopenia (platelet counts), leukopenia (loss of buffy coat), bronchoconstriction (increased airway resistance to fixed airway ventilation), thromboxane A2 production (radioimmunoassay to thromboxane B2) and in vitro aggregation responses of platelets in platelet-rich plasma. Cebus platelets were refractory to PAF-induced aggregation (up to 50 microM) and there was no evidence of thrombocytopenia, elevated thromboxane B2 levels, loss of buffy coat or bronchoconstriction following systemic PAF injection. Animals exhibited reproducible but varying sensitivities to PAF-induced hemoconcentration, where 3.5-30 micrograms/kg PAF (6.6-57 nmol/kg) was required to produce 28-32% increased hematocrit range for the colony. Hemoconcentration induced by PAF in baboons and rhesus occurred at similar doses, suggesting comparable sensitivity. Prior administration of PAF receptor antagonists SRI 63-072 or SRI 63-119 at 3 mg/kg inhibited cebus hemoconcentration responses to 3.5 micrograms/kg PAF by 96% and 100%, respectively. The ED50 values were 0.95 and 0.60 mg/kg, respectively. These results suggest that the cebus exhibits a reproducible hemoconcentration effect to PAF and that these vascular responses can be inhibited by a PAF receptor antagonist.

Animals↗
PubMed1999

Prospects for trichromatic color vision in male Cebus monkeys.

Polymorphic color vision is characteristic of many species of New World monkey. A fundamental feature of the polymorphism is that male monkeys are routinely dichromatic. A recent paper describes an experiment in which Cebus monkeys were required to discriminate between pairs of Munsell color chips (Pessoa VF, Tavares MCH, Aguiar L, Gomes UR, Tomaz C. Color vision discrimination in the capuchin monkey Cebus apella: evidence for trichromaticity. Behav Brain Res 1997;89:285-288). The results were interpreted as demonstrating trichromatic color vision in male Cebus monkeys. An examination of the literature on Cebus. monkey photopigments and results from a replication of the discrimination experiment conducted with dichromatic human subjects cast doubt on this claim.

Animals↗
PubMedDate not supplied

Morphology, dendritic field size, somal size, density, and coverage of M and P retinal ganglion cells of dichromatic Cebus monkeys.

Male Cebus monkeys are all dichromats, but about two thirds of the females are trichromats. M and P retinal ganglion cells were studied in the male Cebus monkey to investigate the relationship of their morphology to retinal eccentricity. Retinal ganglion cells were retrogradely labeled after optic nerve deposits of biocytin to reveal their entire dendritic tree. Cebus M and P ganglion cell morphology revealed by biocytin retrograde filling is similar to that described for macaque and human M and P ganglion cells obtained by in vitro intracellular injection of HRP and neurobiotin. We measured 264 and 441 M and P ganglion cells, respectively. M ganglion cells have larger dendritic field and cell body size than P ganglion cells at any comparable temporal or nasal eccentricity. Dendritic trees of both M and P ganglion cells are smaller in the nasal than in the temporal region at eccentricities greater than 5 mm and 2 mm for M and P ganglion cells, respectively. The depth of terminal dendrites allows identification of both inner and outer subclasses of M and P ganglion cells. The difference in dendritic tree size between inner and outer cells is small or absent. Comparison between Cebus and Macaca shows that M and P ganglion cells have similar sizes in the central retinal region. The results support the view that M and P pathways are similarly organized in diurnal dichromat and trichromat primates.

Animals↗
PubMedDate not supplied

Connectional and neurochemical subdivisions of the pulvinar in Cebus monkeys.

Based on cytoarchitectonic criteria, the primate pulvinar nucleus has been subdivided into medial (PM), lateral (PL), and inferior (PI) regions. However, these subdivisions show no correlation with those established by electrophysiological, immunocytochemical, or neuroanatomical tracer studies. In this work, we studied the connections of the pulvinar nucleus of Cebus monkey with visual areas V1, V2, V4, MT, and PO by means of retrograde fluorescent tracers injected into these areas. Based on the projection zones to cortical visual areas, the visual portion of the pulvinar of Cebus monkey was subdivided into three subregions: P1, P2, and P3, similar to those described in the macaque (Ungerleider et al., 1984). In Cebus, P1 includes the centrolateral portion of traditionally defined PI and adjacent portion of PL. P2 is located in the dorsal portion of PL and P3 includes the medial portion of PI and extends dorsally into adjacent PL and PM. In addition, we studied the histology of the pulvinar using multiple criteria, such as cytoarchitecture and myeloarchitecture; histochemistry for cytochrome oxidase, NADPH-diaphorase, and acetylcholinesterase; and immunocytochemistry for two calcium-binding proteins, calbindin and parvalbumin, and for a neurofilament recognized by the SMI-32 antibody. Some of these stains, mainly calbindin, showed additional subdivisions of the Cebus pulvinar, beyond the traditional PI, PL, and PM. Based on this immunohistochemical staining, the border of PI is moved dorsally above the brachium of the superior colliculus and PI can be subdivided in five regions (PI(P), PI(M), PI(C), PI(L), and PI(LS)). Regions P1, P2, and P3 defined based on efferent connections with cortical visual areas are not architectonically/neurochemically homogeneous. Rather they appear to consist of further chemoarchitectonic subdivisions. These distinct histochemical regions might be related to different functional modules of visual processing within one connectional area.

Acetylcholinesterase↗
PubMed2003

The muscarinic M1/M4 receptor agonist xanomeline exhibits antipsychotic-like activity in Cebus apella monkeys.

Xanomeline is a muscarinic M(1)/M(4) preferring receptor agonist with little or no affinity for dopamine receptors. The compound reduces psychotic-like symptoms in patients with Alzheimer's disease and exhibits an antipsychotic-like profile in rodents without inducing extrapyramidal side effects (EPS) at therapeutically relevant doses. In the present study, we examined whether the xanomeline-induced functional dopamine antagonism found in rodent studies could also be observed in nonhuman primates. In addition, we studied whether the lack of EPS observed in rodents also applies to primates. To this end, we investigated the effects of xanomeline on the behavior induced by D-amphetamine and (-)-apomorphine in drug-naive Cebus apella monkeys. Antipsychotic compounds antagonize amphetamine-induced motor unrest and stereotypies in this species. Xanomeline inhibited D-amphetamine-induced motor unrest, stereotypies and arousal as well as apomorphine-induced stereotypies and arousal in drug-naive Cebus apella monkeys. Xanomeline did not induce EPS but vomiting occurred in some monkeys at high doses, in accordance with emetic events observed in Alzheimer patients following xanomeline administration. Even when xanomeline was tested in EPS-sensitized Cebus apella monkeys, EPS were not observed at the dose range of xanomeline used in the D-amphetamine-apomorphine combination study (0.5-3 mg/kg). However, when xanomeline was tested at 4 mg/kg, moderate dystonia was seen in two out of three monkeys. It is concluded that xanomeline inhibits D-amphetamine- and (-)-apomorphine-induced behavior in Cebus apella monkeys at doses that do not cause EPS. These data further substantiate that muscarinic receptor agonists may be useful in the pharmacological treatment of psychosis.

Amphetamine↗
PubMed1996

Functionally defined smooth and saccadic eye movement subregions in the frontal eye field of Cebus monkeys.

1. Intracortical microstimulation was used to localize and define the smooth and saccadic eye movement subregions of the frontal eye field (FEF) and the supplementary eye field (SEF) in nine hemispheres of six Cebus apella monkeys and to map the hand/arm areas in the dorsal premotor area and other adjacent areas in five hemispheres of three C. apella monkeys. Monkeys were anesthetized during experiments with Telazol, a dissociative agent that has no significant effect on microstimulation-induced eye movement parameters (current threshold, velocity, and duration). The functional subregions were defined with the use of low threshold current (< or = 50 microA). Electrically elicited eye movements were videotaped and quantified. The two types of eye movements were clearly distinguished by their significantly different duration and velocity (P < 0.0001) and their different responses to long stimulus trains. 2. The saccadic subregion of the FEF in Cebus monkeys is in the same location as in macaque monkeys (Walker's areas 8a and 45). Most of the functional and anatomic characteristics of the saccadic subregion of Cebus are the same as those reported in the saccadic FEF subregion of macaque monkeys. 3. A subregion in which only smooth eye movements were evoked was found in the posterior shoulder of the superior arcuate sulcus near its medial tip. A band of inexcitable cortex separated the SEF and this smooth eye movement subregion of the FEF. This supports the proposal that the smooth eye movement subregion is independent of the SEF but is analogous to the saccadic subregion of the FEF. The existence of two subregions of the FEF was further confirmed by single-unit recording results. It is proposed that the smooth eye movement subregion in Cebus monkeys may be comparable with the one described in macaque monkeys. 4. Both saccadic and smooth eye movements were also reliably evoked in the SEF in each hemisphere studied. This result strongly indicates that the SEF is concerned with not only saccadic eye movements, as previously reported, but also with smooth (pursuit) eye movements.

Animals↗
PubMed1989

Acute extrapyramidal syndrome in Cebus monkeys: development mediated by dopamine D2 but not D1 receptors.

The present study assessed the role of dopamine D1 and D2 receptors in the production of an extrapyramidal syndrome (EPS) in Cebus apella monkeys. Previous studies have shown the development of EPS in both old and new world monkeys with haloperidol administration. We now report that repeated weekly administration of a selective D1 antagonist, SCH 23390, does not produce this syndrome in cebus monkeys. Cebus monkeys were treated with either vehicle (n = 6), the specific D2 antagonist haloperidol (0.3 mg/kg p.o., n = 9) or the specific D1 antagonist SCH 23390 (10.0 mg/kg p.o., n = 9) once a week for approximately 1 year and behavioral effects were observed and scored. The drug doses used in this study produced similar sedative scores when given acutely and sedation increased over the first 12 weeks of the study for both treatment groups. However, by the 12th week of dosing with haloperidol all the monkeys showed a profound EPS characterized by limb extensions, head pushing, tongue protrusions and sometimes severe biting movements. In contrast, none of the SCH 23390-treated monkeys showed any abnormal movements, suggesting D1 antagonists have a low EPS side-effect liability. The profile of the incidence of EPS seen with classical neuroleptic drugs in cebus monkeys and their blockade of EPS by anticholinergic drugs mimics the profile seen in humans. The models presented appear to be predictive of the production of the EPS in humans and could be used to screen neuroleptics for EPS liability. Furthermore, the EPS is probably due to the selective blockade of dopamine D2 receptors with its associated enhancement of cholinergic neurotransmission.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗