RESUMEN
1. In this report the postnatal differentiation of the hypothalamic ventromedial nucleus (VMN) was studied. The main maturational changes detected at the fine structural level occurred between 10 and 20 days of postnatal life. 2. In 5-day-old rats the majority of neurons was undifferentiated, with rudimentary cytoplasmic organelles. Dendritic profiles presented an empty appearance due to an electron-lucent matrix and scarce content of organelles. 3. At 10 days there was a significant proliferation of cytoplasmic organelles in the perikaryon, mainly of those involved in protein biosynthesis as the rough endoplasmic reticulum (RER) and the Golgi complex. 4. After 20 days of age the VMN neurons acquired the cytological appearance of adult neurons, with well-organized RER, Golgi complexes, and pleomorphic mitochondria. Concurrent with these changes, there was a marked development of other organelles in the neuropil, which was accompanied by an increase in synaptic density and differentiation of their subsynaptic structures.
Asunto(s)
Núcleo Hipotalámico Ventromedial/crecimiento & desarrollo , Animales , Diferenciación Celular , Femenino , Masculino , Microscopía Electrónica , Neuronas/citología , Orgánulos/ultraestructura , Ratas , Ratas Endogámicas/crecimiento & desarrollo , Sinapsis/ultraestructura , Núcleo Hipotalámico Ventromedial/ultraestructuraRESUMEN
Stereological electron microscopic analysis of the rat hypothalamic ventromedial nucleus (VMN) throughout postnatal development revealed that synaptogenesis takes place up to day 45. Our results disclosed a sexual dimorphism in the synaptic organization of the neuropil of the ventrolateral (VL) subdivision of the VMN. The numerical densities of spine and shaft synapses in the adult male were higher than in the female. A dimorphic pattern in the numerical density of spine synapses occurred as early as day 5, and was present throughout postnatal life, even though in the adult rats both spine and shaft synapses were sexually dimorphic. Neonatal treatment of female rats with testosterone increased the numerical density of axodendritic synapses, inducing a pattern similar to the adult male. On the other hand, administration of tamoxifen to newborn male rats significantly reduced the numerical density of spine synapses to levels comparable to normal female rats.
Asunto(s)
Hormonas/farmacología , Sinapsis/fisiología , Núcleo Hipotalámico Ventromedial/ultraestructura , Envejecimiento/fisiología , Animales , Axones/ultraestructura , Diferenciación Celular , Dendritas/ultraestructura , Femenino , Masculino , Microscopía Electrónica , Ratas , Ratas Endogámicas , Sinapsis/efectos de los fármacos , Tamoxifeno/farmacología , Testosterona/farmacología , Núcleo Hipotalámico Ventromedial/efectos de los fármacosRESUMEN
Hemos empleado 40 ratas macho, cepa Wistar, de 2 meses de edad. Los animales se dividieron en 20 ratas controles (10 ratas intactas y 10 ratas sometidas a operación simulada), y 20 animales experimentales (10 sacrificados al mes y 10 sacrificados a los dos meses de la operación quirúrgica). El método experimental fue la extirpación extereotáxica del nucleo amigdalino basolateral de la amígala cerebral. Hemos estudiado la ultraestructura del nucleo ventromedial del hipotálamo. Hemos observado un incremento de la actividad de las neuronas del nucleo hipotalámico ventromedial en los animales experimentales (aumento del retículo endodplasmático rugoso, del aparato de Golgi, de los cuerpos densos, y de las mitocondrias con matriz densa), y en las sinapsis (un incremento de las vesículas y de los gránulos densos). Nuestros resultados demuestran que el nucleo amigdalino basolateral ejerce un efecto inhibidor de la actividad neuronal del nucleo hipotalámico ventromedial