Selective reduction of serotonin immunoreactivity in some forebrain regions of rats induced by acute methamphetamine treatment; quantitative morphometric analysis by serotonin immunocytochemistry.

The influence of acute methamphetamine treatment on serotonin-like immunoreactive axons was studied in the rat forebrain. Animals, sacrificed 90 min after i.p. injection of methamphetamine (16 mg/kg) or saline, were processed for immunocytochemistry using serotonin antiserum. The numerical density of immunoreactive boutons of terminals and varicosities was quantitatively analyzed by a computer-assisted image analyzer. Compared with the control, administration of methamphetamine caused varying degrees of reduction in the numerical density in several forebrain regions. A high decrement (over -90%) was found in deep layers of the cerebral cortex, striatum and thalamic paraventricular nucleus, while a less prominent reduction (about -50%) was seen in such regions as the suprachiasmatic nucleus and basolateral amygdaloid nucleus. Moreover, superficial layers of the cerebral cortex contained uncommon features of immunopositive axons which were characterized by intensely stained fibers with large varicosities. The results suggest that the rat forebrain contains at least two types of serotonin nerves, one very sensitive to methamphetamine and another relatively insensitive or resistant to it.

Bifunctional roles of catecholamines in the development of amygdala kindling demonstrated by continuous intra-amygdala infusion of 6-hydroxydopamine.

Details of seizure stage progression in amygdala kindling were studied in the cat under local denervation of catecholamine input to the amygdala. A chemitrode was used for both electrical stimulation and continuous infusion of 6-hydroxydopamine. The extent of denervation was confirmed by fluorescence histochemistry. The result has indicated that catecholamine afferents to the amygdala exert biphasic roles in normal kindling: inhibitory in the early local and late generalized seizure stages, whereas facilitatory in the intermediate stage.

Further confirmation of heterogeneity of the rat striatum: different mosaic patterns of dopamine fibers after administration of methamphetamine or reserpine.

Heterogeneity of adult rat neostriatum has been studied by fluorescence histochemistry. The distribution of dopamine nerve fibers and terminals, known normally to be homogeneous, tended to become heterogeneous after administration of methamphetamine or reserpine. Both drugs caused mosaic formations of fluorescent dopamine axons and terminals, though a minor difference was present in the pattern of distribution. The results indicate that the striatum possesses at least two types of dopamine nerve terminals, sensitive and relatively insensitive for the two catecholamine depletors.

Noradrenergic axon terminals in the substantia gelatinosa of the rat spinal cord: an electron-microscopic study using glyoxylic acid-potassium permanganate fixation.

The noradrenergic terminals in the substantia gelatinosa of the dorsal horn of the cervical spinal cord of the rat were investigated by means of the histofluorescence technique and electron-microscopic cytochemistry using the glyoxylic acid-KMnO4 fixation technique. In accordance with the topographical distribution of fluorescent catecholaminergic fibers, noradrenergic terminals containing small granular vesicles were frequently observed electron microscopically in the outer layer of the substantial gelatinosa. These terminals were most frequently found to appose (without showing typical synaptic features, small-caliber dendrites, spine apparatus, and rarely, large caliber dendrites. Only in a few cases, the noradrenergic terminals exhibited typical synaptic contacts with dendritic elements of small size. In addition, noradrenergic terminals apposed non-noradrenergic terminals containing small agranular vesicles. In rats bearing surgical lesions of the dorsal roots, no noradrenergic terminal were found in contact with the degenerated axon terminals in the substantia gelatinosa. These findings suggest that the noradrenergic afferents to the substantia gelatinosa may exert their influence on sensory transmission via dorsal horn cells.

Fine structure of noradrenaline nerve terminals in the dorsomedial portion of the nucleus tractus solitarii as demonstrated by a modified potassium permanganate method.

Fine structure of the noradrenaline (NA) nerve terminals in the dorsomedial portion of the nucleus tractus solitarii (NTS) was investigated by glyoxylic acid-potassium permanganate fixation method. The NA nerve terminals in this area contained a large number of small cored vesicles (SCV) (about 400-600 A in diameter) together with a few large cored vesicles (LCV) (about 1000 A in diameter). The most frequent feature of NA nerve terminals observed in this area was axo-dendritic contact. An axo-axonic contact between NA and non-NA terminals was also occasionally identified, while no axo-somatic contact was found in this area as far as examined. At the contact zone between NA terminals and other neuronal elements, the following profiles suggestive of synapse-like contact were identified: 1) somewhat dense material between contact membranes (intersynaptic filaments); 2) a slight accumulation of dense material adjacent to postcontact membranes; 3) disarrangement of contact membranes and enlargement of the space between these membranes; 4) aggregation of SCV and LCV to contact membranes. Finally it should be emphasized that NA nerve terminals often made a neuronal cluster or rosette with other neuronal elements, suggestive of a complicated role of NA on NTS function.