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PubMed1988

Connections of the primary auditory cortex in the common marmoset, Callithrix jacchus jacchus.

The afferent and efferent connections of the primary auditory cortex (AI) of common marmosets were traced following small injections of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) made at best frequency (BF)-defined sites in the AI. After the injections the animals remained anesthetized for 15-23 hours; they were then perfused transcardially with fixative and the brains were processed for WGA-HRP reaction product. Examination of the disposition of labelled material revealed the following results. First, patches of terminal labelling, and to a lesser extent retrograde labelling, were found outside the injection site in the ipsilateral cortex rostral and caudal to the AI. Second, the region of the contralateral cortex corresponding to the injection site contained labelled terminals throughout the depth of the cortex; labelled neurons were found in the middle layers. Third, in each experiment a discrete region of the medial geniculate body (MG) contained retrogradely labelled neurons interspersed with anterogradely labelled terminals. These regions had a banded appearance, were found in the dorsal and rostral half of the MG, and shifted in location progressively dorsalward as the injection site BF increased. The presence of projection zones rostral and caudal to the AI of marmosets, and the disposition of the MG sources of projection in relation to BF, are similar to observations made on other New World monkeys. The ipsilateral corticocortical projections confirm electrophysiological evidence suggesting the existence of auditory fields rostral and caudal to the AI. The thalamocortical auditory system of the marmoset appears relatively simple, with a comparatively undifferentiated MG projecting to a cortical auditory system dominated by a large AI.

Animals↗
PubMed1988

Distribution and some projections of cholinergic neurons in the brain of the common marmoset, Callithrix jacchus.

The distribution of choline acetyltransferase-immunoreactive (ChAT-IR) neurons was studied in the brain of the common marmoset by using immunohistochemistry. ChAT-IR neurons were found in the medial septal nucleus, vertical and horizontal limb nuclei of the diagonal band, the nucleus basalis of Meynert, pedunculopontine nucleus and laterodorsal tegmental nucleus, and also in the striatum, habenula, and brainstem cranial nerve motor nuclei. The organization of ChAT-IR neurons in the basal forebrain, midbrain, and pons is consistent with the Ch1-Ch6 nomenclature introduced by Mesulam et al. ('83). The combination of the retrograde transport of HRP-WGA with ChAT immunohistochemistry revealed the distribution of neurons in the Ch4 cell group projecting to the dorsolateral prefrontal cortex. The activity of ChAT was highest in limbic cortical structures, such as the hippocampus, and lowest in association areas of the neocortex. Lesions at various loci in the basal forebrain resulted in differential patterns of ChAT loss in the cortex, which suggests some degree of topographical organization of Ch4 projections to the cortical mantle.

Animals↗
PubMed1979

The retino-geniculo-cortical pathway in Callithrix. II. The geniculo-cortical projection.

After monocular injections of tritiated tracer precursors and transneuronal transport of tritiated compounds, a continuous band of radioactivity in layer IV of striate cortex of Callithrf the crossed and uncrossed retino-cortical pathways. Comparison with the organization of these pathways in other primates suggests that a segregation of the retino-cortical pathways of opposite ocularities into alternating ocular dominance columns in striate cortex has developed independently in the different primate lines. The significance is discussed of the weak labeling of the region of area 17 representing the central retina as compared to the representation of the peripheral retina.

Animals↗
PubMed1977

Topographically organized reciprocal connections between areas 17 and MT (visual area of superior temporal sulcus) in the marmoset Callithrix jacchus.

With the aid of the techniques of tracing axonal pathways by anterograde fiber degeneration, and by anterograde (autoradiography) and retrograde (HRP-histochemistry) axoplasmic transport, it could be shown that area 17 projects in a topographically and visuotopically organized manner onto the temporal visual area MT. The fibers of this association system originate from pyramidal cells in layer IIIc, and from the solitary cells of Meynert; they terminate in layers IV and III of area MT. A correspondingly organized system of countercurrent fibers originates from pyramidal cells in layers III/II and V/VI of area MT and terminates separately in layers VI, IIIc and I of area 17.

Animals↗
PubMed1983

Timing of ovulation and implantation in the common marmoset, Callithrix jacchus, by monitoring of estrogens and 6 beta-hydroxypregnanolone in urine.

Urinary estrogen and 6 beta-hydroxypregnanolone excretions have been determined in female marmosets by means of HPTLC. The levels observed in cycling females during implantation and abortion are reported. Hormone analysis revealed a characteristic pattern showing cyclic fluctuations of estrogens and progesterone. Estrogen metabolites increase during the follicular phase up to 1 microgram/ml, the progesterone metabolite level rises to 1.2 micrograms/ml urine during the luteal phase. Maximum values of both are superimposed in many cases. Ovulatory cycles can be monitored by following estrogen and progesterone metabolites in urine samples. Thus ovulation and the onset of pregnancy can be estimated with a precision of +/- 24 h (or less).

17-alpha-Hydroxypregnenolone↗
PubMed1981

Pharmacologic manipulations of brain catecholamines and the behavior of Callithrix jacchus (marmoset).

In experiment 1, groups of marmosets were injected with 50 - 200 mg/kg L-dopa, 0.5 - 2.0 mg/kg apomorphine (AP), or 0.5 - 5.0 mg/kg methamphetamine. The number of head movements, number of body movements, number of times the tongue was extended, and the time the animal remained in an upright posture were scored during a 90-min period after the injections. L-Dopa and AP induced large dose-dependent increases in body movements and time in upright posture. Furthermore, the smallest dose of AP induced self-destructive behavior. The main effect produced by methamphetamine was a constant turning of the head with the body remaining still. In experiment 2, the marmosets were treated with alpha-methyl-p-tyrosine (AMPT) or haloperidol prior to challenge with AP or methamphetamine. Haloperidol blocked most of the effects of both drugs, while AMPT blocked only methamphetamine effects. In experiment 3, marmosets were injected with increasing doses of haloperidol for 22 days. Upon withdrawal of the neuroleptic, methamphetamine and AP effects were not increased, suggesting absence of supersensitivity of dopaminergic receptors.

Animals↗
PubMed1988

Effects of hypothalamic lesions upon the sexual and social behaviour of the male common marmoset (Callithrix jacchus).

The sexual and associated behaviour of 10 adult male marmosets was recorded during pair tests with ovariectomized females, before and after bilateral thermal lesions of the hypothalamus. Four sham-lesioned males served as controls. Lesions varied in volume from 1.49 to 3.28 mm3 and extended from the ventromedial hypothalamus to the diagonal band of Broca. Precopulatory behaviours (anticipatory erections, tongue flicking and anogenital investigations of the female) as well as frequencies of mounting, intromission and ejaculation decreased in lesioned males. The greatest suppression of sexual behaviour occurred after lesioning the anterior hypothalamus (AH), beneath the anterior commissure, or at the junction of the AH with the preoptic area (POA). Lesions confined to the POA had less profound behavioural effects. Treating ovariectomized females with estradiol stimulated their proceptivity but had no consistent effects upon the males' behaviour. Lesioned males did not exhibit signs of social withdrawal and frequencies of allogrooming or grooming invitations increased post-operatively. Preliminary studies on intermale aggression indicated that lesions which had the greatest effect upon sexual behaviour also tended to decrease aggressive interactions with other males. Hypothalamic lesions did not affect plasma testosterone levels, except in one male and only one animal showed signs of ill health (weight loss and hypothermia) post-operatively. These results show that damage to the AH or AH-POA junction in male marmosets causes a profound suppression of sexual 'arousal' and copulatory behaviour and that such affects are not due to androgen insufficiency or other, non-specific, side effects of neural damage.

Aggression↗
PubMed1989

Loss of ocular dominance columns with maturity in the monkey, Callithrix jacchus.

Previous studies have shown that adult marmosets lack ocular dominance columns (ODC) in area 17, but that ODCs can be demonstrated upon visual deprivation. The present results, obtained by transneuronal transport of WGA-HRP, indicate that ODCs normally develop in juvenile marmosets but disappear before the animal reaches maturity. The findings suggest that formation of ODCs during ontogenesis, and their persistence through adulthood, are different developmental processes depending on different mechanisms.

Aging↗