Biomedical subjects

N Giry

Publications and source records attributed to N Giry.

4 recordsLinked to original sources

PubMed1992

Effect of administration of an analog of LHRH on appetitive learning in young and middle-aged female rats.

Hypothalamic luteinizing hormone-releasing hormone (LH-RH) had been reported to induce changes in defensive learning. In middle age, females exhibit a decline in their reproductive axis. Several studies in rodents suggested that hypothalamic LHRH function deteriorated in middle-aged females. Our experiments compare T-maze learning in young and middle-aged female rats and study the effect of administration of an analog of LHRH, D-Trp6-LHRH. The ovarian action of the analog was studied and a gonadectomized control group was added. No differences were observed between young and middle-aged females in acquisition, retention, and reversal of a simple discrimination in the T-maze. However, after removal of motor and spatial cues acquisition of the discrimination on visual cues was impaired in middle-aged females compared to young mature ones. Administration of D-Trp6-LHRH enhanced performance during the visual discrimination in younger females and had no action in middle-aged ones, whereas it inhibited ovary function in both groups. Ovariectomy had no effect. These results suggest a direct effect of the analog of LHRH on the CNS and show that this peptide fails to counteract the deleterious effect of age on performance.

Aging↗

PubMed1991

Acquisition of a matching-to-sample task in young and middle-aged male and female rats.

Male and female rats were trained in a water-reinforced matching-to-sample task. The rule was acquired more rapidly by the females. After initial training, the retention of the rule was measured when the rats were twelve and 14 months old. The performance of neither group was modified at twelve months, but at 14 months, while no change appeared in the performance of males, females showed a drop in correct responses. Training in a modified device which made the task more difficult induced no changes in performance. Final training (at 18 months) showed the drop in performance in females had persisted. The decline of performance in middle-aged females might be related to the ageing female reproductive system.

Aging↗

PubMed1988

Immunohistochemical localisation of nerve growth factor-like protein in the organ of Corti of the developing rat.

The presence of nerve growth factor (NGF)-like protein was investigated in the cochlea of the developing rat between birth and postnatal day 30, by the indirect immunofluorescence technique. Nerve growth factor-like protein could be detected from birth up to day 8. The immunostaining was localised within the hair mainly above their nuclei. No NGF-like immunoreactivity was observed in spiral ganglion cells. The data suggest that NGF acts as a neurotrophic factor, especially for efferent endings in the developing cochlea.

Aging↗

PubMed1987

Factors affecting the onset of inner ear function.

The developing inner ear receptors have a very significant influence on the onset of stato-acoustic function and on its evolution. The factors which prevent the stato-acoustic system from functioning are called 'the limiting factors'. At present, it is possible to postulate that these factors are restricted to the inner ear cells and related structures. At least four places are particularly relevant for the onset of function: (1) connections of the apical part of hair cell with the tectorial membrane; (2) the internal structure of hair cell; (3) connections between the base of the hair cell and nerve fibers; (4) the ganglion cell with its processes. Special emphasis is devoted to the apical part of the inner hair cell and its connections to the tectorial membrane which are considered as very important for the onset of the cochlear function. For the labyrinth, it is technically difficult to determine precisely the onset of function because of its early prenatal onset. Nevertheless, it is postulated that the limiting factors for the onset of function are also related to certain components of hair cells.

Animals↗