Morphometric analysis of feedforward pathways from the primary somatosensory area (S1) of rats

We used biotinylated dextran amine (BDA) to anterogradely label individual axons projecting from primary somatosensory cortex (S1) to four different cortical areas in rats. A major goal was to determine whether axon terminals in these target areas shared morphometric similarities based on the shape of individual terminal arbors and the density of two bouton types: en passant (Bp) and terminaux (Bt). Evidence from tridimensional reconstructions of isolated axon terminal fragments (n=111) did support a degree of morphological heterogeneity establishing two broad groups of axon terminals. Morphological parameters associated with the complexity of terminal arbors and the proportion of beaded Bp vs stalked Bt were found to differ significantly in these two groups following a discriminant function statistical analysis across axon fragments. Interestingly, both groups occurred in all four target areas, possibly consistent with a commonality of presynaptic processing of tactile information. These findings lay the ground for additional work aiming to investigate synaptic function at the single bouton level and see how this might be associated with emerging properties in postsynaptic targets.

Role of catecholaminergic terminals in the preoptic area in behavioural thermoregulation in rats.

This study was conducted to find out the role of the catecholaminergic terminals in the preoptic area (POA) in selection of ambient temperature in rats. The adult male Wistar rats (n = 6) were allowed to choose between three ambient temperatures (24 degrees C, 27 degrees C and 30 degrees C). Rats could move about freely from one ambient temperature to another, in a specially designed environmental chamber having three interconnected compartments, which were maintained at the above mentioned temperature. The results show that the normal rats preferred to stay at 27 degrees C both during day and night. After the lesion of catecholaminergic terminals in the POA with 6-hydroxydopamine (6-OHDA), the animals preferred 24 degrees C on the third and seventh day and 27 degrees C on the fourteenth and twenty first day after lesion. The alteration in thermal preference was associated with an elevation of rectal temperature. The study suggests that the catecholaminergic terminals of the POA play an important role in integrating behavioural and non-behavioural thermoregulatory responses, but in its absence the rest of the brain takes over some of its functions.

Liberación de neuropéptido tirosina (NPY) de los terminales nerviosos en vasos mamarios / Liberation of tyrosine neuropeptide (NPY) from mammary vessels nerve endings

En este estudio caracterizamos la liberación de NPY de biopsias de la arteria y vena mamaria. Se induce la liberación de los neurotransmisores por medio de despolarización eléctrica de los nervios simpáticos perivasculares. Con estímulo de 70 V, 0,5 msec, 40 Hz por 5 min, segmentos de la arteria mamaria liberan 17,7 ñ 6,7 fmol (n=4) de NPY, la vena libera 4,3 ñ 1,5 fmol (n=4), valores que corresponden a un 1-2 por ciento del NPY en la biopsia. El NPY liberado por estímulo eléctrico no es metabolizado en la sinapsis neuroefectora. La liberación del NPY al medio de superfusión tiene un curso temporal lento, la máxima liberación ocurre a los 10 min del estímulo. La liberación del NPY es dependiente de la duración del estímulo (coeficiente de correlación = 0,647, p<0,01); y de la frecuencia de estimulación (coeficiente de correlación = 0,611, p<0,05), indicando que la liberación es un proceso controlado por la frecuencia de la descarga y por la intensidad del estímulo simpático vasomotor. El proceso de liberación es dependiente del calcio, ya que en ausencia de calcio extremo, la liberación de NPY se reduce en 78 por ciento. El NPY actúa sobre receptores postsinápticos, donde produce un efecto facilitador significativo de la acción vasomotora de NA y ATP. En conclusión, NPY se libera al espacio sináptico por exocitosis, donde participa junto a NA y ATP en la regulación del tono vasomotor simpático

Morphometric analysis of intrinsic axon terminals of Cebus monkey area 17

A morphological study of intrinsic projections in area 17 of Cebus monkey was conducted after iontophoretic injection of biocytin. Thirty axon terminals located in supragranular layers were qualitatively and quantitatively analyzed using 3-D automatic microscopy. Three types of axon terminals could be identified: Ia, Ib and II. Group I was characterized by a sparse and/or long-distance branch pattern, while type II presented compact and localized arborization. Ia axon terminals formed "clusters" and "terminaux"boutons while Ib did not. On overage, group II axon terminals tended to present straight or obtuse branching angles and a much more ramified pattern, and occupy a smaller cortical territory with shorter intermediate segments and higher density of synaptic potential sites than group I. The common characteristics of group I included innervation of larger cortical territories, longer intermediate segments, acute branching angles and lower synaptic density compared to group II. The results are compatible with the major subdivisions of neocortical neuronal morphology that classifies them as smooth and spine neurons. Smooth neurons may be related to axon terminals of group II while spine neurons may be related to group I.

Liberación estriatal de un análogo de aminoácidos excitatorios en un modelo experimental de hipoxia cerebral in vitro / Striatal release of a tritiated analog of excitatory amino acid in a in vitro experimental model of brain hypoxia

Este trabajo presenta la metodología experimental de un modelo de hipoxia cerebral in vitro. El modelo fue empleado para evaluar la liberación de un análogo no metabolizable de glutamato en condiciones de hipoxia, como un reflejo del estado funcional de los terminales nerviosos glutamatérgicos en condiciones de hipoxia, observándose una significativa liberación del marcador tritiado en relación a la hipoxia, lo cual concuerda con hallazgos previos tanto en animales de experimentación como en seres humanos. La metodología presentada es simple y permite manejar a voluntad del investigador una serie de parámetros relevantes desde el punto de vista fisiopatológico de la injuria neuronal por hipoxia, de un modo que es imposible de lograr en los estudios in vivo