| dc.contributor.author | MacDonald, Michael Carleton. | en_US |
| dc.date.accessioned | 2014-10-21T12:34:40Z | |
| dc.date.available | 1990 | |
| dc.date.issued | 1990 | en_US |
| dc.identifier.other | AAINN64430 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55181 | |
| dc.description | This thesis examines both the excitatory and inhibitory neural mechanisms which regulate sexual maturation in the female rat. Single daily prepubertal injections of the excitatory glutamate agonist N-methyl-D-aspartate (NMDA) significantly advanced the day of first ovulation (vaginal opening; V.O.) whereas similar treatment with the NMDA antagonists MK-801 or dextrorphan effectively delayed but did not prevent V.O. NMDA readily stimulated LH secretion in prepubertal rats, an effect which could be blocked by MK-801. NMDA-induced hypothalamic cellular activity was immunocytochemically localized through expression of the early-response gene (proto-oncogene) c-fos and was also prevented by pre-injection of MK-801. Neonatal administration of monosodium glutamate (MSG), known to destroy glutamatergic neurons in the arcuate nucleus (ARCN), significantly advanced the time of V.O., possibly by the removal of inhibitory $\beta$-endorphin neurons. These results suggest that the excitatory neurotransmitter glutamate may be important in the control of GnRH/LH release and the process of sexual maturation. | en_US |
| dc.description | The inhibitory opiatergic regulation of puberty was examined using two opiate agonists, morphine and fentanyl citrate. When these were administered orally, via the drinking water, or by subcutaneous osmotic minipumps, V.O. was significantly delayed but not prevented. This suggests that the hypothalamic opioid system can be desensitized to allow V.O. to occur even in the face of continuous agonist treatment. However, a combination of fentanyl and MK-801 considerably extends the delay in maturation. This suggests the presence of distinct but converging excitatory and inhibitory pathways. Finally, in vitro micropunch studies demonstrated that the mu agonists DAGO and fentanyl can decrease hypothalamic cell surface mu-opioid receptor number without affecting binding affinity. This is a simple but effective technique with which to examine opioid receptor regulation. | en_US |
| dc.description | These studies provide convincing evidence that excitatory amino acids and endogenous opioid peptides play a critical role in the neural control of sexual maturation in the female rat. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1990. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Neuroscience. | en_US |
| dc.subject | Biology, Animal Physiology. | en_US |
| dc.title | Excitatory and inhibitory neural control of sexual maturation in the female rat. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
