Kenichi Takatsuki

Ontogeny of substance P-containing neuron system of the rat: Immunohistochemical analysis—I. Forebrain and upper brain stem

The ontogeny of substance P-containing neuron system in the forebrain and upper brain stem of the rat was investigated by means of the indirect immunofluorescence technique. Substance P-positive structures first appeared in the primordium of the epithalamus and the area which surrounded the commissura posterior of the rat fetus corresponding to gestational day 14 (10-12 mm embryos). On and after gestational day 14, substance P-positive structures gradually made their appearance in various areas of the forebrain and upper brain stem. Substance P-positive structures thus continued to increase in number and in density during the fetus and perinatal stage and showed histochemically maximum content at the stage between postnatal days 5 and 15. After then, substance P-positive neurons tended to decrease in number as the rats grew, while substance P-positive fibers maintained in general their strong immunoreactivity even in the adult rats. The present study demonstrates that substance P-positive structures appear at a very early ontogenetical stage. This suggests that substance P might play an important role in the development of the forebrain and upper brain stem in addition to its neurotransmitter or neuromodulator functions.

Ontogeny of substance P-containing neuron system of the rat: Immunohistochemical analysis—II. Lower brain stem

Ontogeny of the substance P neuron system in the lower brain stem of the rat was investigated by means of the indirect immunofluorescence technique. Substance P-positive structures (cells and fibers) first appeared in the primordium of the ventral part of the nucleus tractus spinalis nervi trigemini (nVs), in the reticular formation between nucleus reticularis lateralis and nVs, and in the reticular formation between nVs and nucleus originis nervi facialis, respectively, at gestational day 14. After that time, substance P-positive structures made their appearance gradually in various areas of the lower brain stem. The present study demonstrates that substance P-positive structures appear at a very early ontogenetical stage, which suggests that substance P may play a role in the development of the lower brain stem in addition to its role as a neurotransmitter or neuromodulator.

Experimental immunohistochemical studies on the amygdalofugal peptidergic (substance P and somatostatin) fibers in the stria terminals of the rat

The amygdalofugal substance P (SP) and somatostatin (SRIF) neuron systems in the stria terminalis (ST) were investigated by means of the indirect immunofluorescence technique of Coons. SP- and SRIF-positive cells were mainly located in the area (Amc) between the central (ac) and medial (am) amygdaloid nuclei. Some extended medially into the am and laterally into the ac. Destruction of the Amc resulted in a marked reduction of SP- and SRIF-positive fibers in the ST. Furthermore, a substantial decrease in SP-positive fibers was seen in the dorsal part of the bed nucleus of the ST (stb), there was a small decrease in the SP-positive fibers in the lateral hypothalamus (LH), a significant decrease in the SRIF-positive fibers in the lateroventral part of the anterior hypothalamic nucleus (lvAH), and a small decrease in the SRIF-positive fibers in the LH. These facts indicate that the origins of a number of SP- and SRIF-positive fibers are the Amc and that the amygdalofugal SP pathway in the ST innervates stb and LH and the amygdalofugal SRIF pathway in the ST projects to lvAH and LH.

Ontogeny of somatostatin-containing neuron system of the rat cerebellum including its fiber connections: an experimental and immunohistochemical analysis.

Ontogeny of somatostatin (SRIF) neuron system of the rat cerebellum was investigated by means of the indirect immunofluorescent method. In addition, several operations were performed to provide the evidence of understanding the cerebellar SRIF innervation. SRIF-positive structures appeared in the primordium of the cerebellum of the fetus at gestational day 16 (14-15 mm embryos). From that time on, SRIF-positive structures identified in the cerebellum increased in number and the greatest number of SRIF-positive structures were detected in the cerebellum of the rat between newborn and 7-day-olds. Afterwards, these structures decreased remarkably in number and only a few if any SRIF-positive structures were observed in the cerebellum of the adult rats. These facts might suggest that SRIF might perform some important roles in the development of the cerebellum. The present study further elucidated that cerebellar SRIF was supplied by at least two types of sources; one was situated within the cerebellum and the other in the extracerebellar regions. The former one innervates mainly the vermis and partly the hemisphere, while the latter one projects mainly to the hemisphere and partly to the vermis.

Experimental and immunohistochemical studies on the cerebellar substance p of the rat: Localization, postnatal ontogeny and ways of entry to the cerebellum

With the indirect immunofluorescence technique, the localization (including the postnatal ontogeny) of substance P in the cerebellum, and the ways of entry of substance P-containing fibers into the cerebellum were explored. In the newborn rat cerebellum, dense fiber bands of axons with substance P-like immunoreactivity which can be traced to the lower brain stem are found. These fibers are also traceable to the developing granular cell layer. Two weeks after birth, however, substance P-containing structures seen in the cerebellum begin to decrease progressively and in the cerebellum of the adult rats, only a small amount of substance P-containing structures is observed. The present study established that substance P-containing fibers are mostly derived from extracerebellar substance P-containing cells and demonstrated the presence of three sites of entry of these substance P-containing fibers to the cerebellum, via (1) the inferior cerebellar peduncle, (2) the fasciculus uncinatus and (3) the middle cerebellar peduncle, respectively. Following deafferentation of the cerebellum, substance P-accumulating fibers are observed only ventral to the lesion (i.e. on the brain stem side), while in the cerebellum a remarkable decrease of substance P-containing fibers is seen and no substance P-accumulating fibers are found dorsal to the lesion (cerebellar side).

Evidence for the existence of a substance P-containing pathway from the nucleus laterodorsalis tegmenti (Castaldi) to the medial frontal cortex of the rat

A long ascending substance P (SP)-containing pathway from the nucleus laterodorsalis tegmenti (TLD) to the medial frontal cortex (MFC) has been demonstrated by means of experimental immunohistochemical procedures. The unilateral destruction of the TLD, which contains numerous SP-like immunoreactive (SPLI) cells, resulted in a marked ipsilateral decrease in the SPLI fibers in the MFC.

Somatostatin in the auditory system of the rat

The present study clearly disclosed that the auditory system of the neonatal rat contains a large number of somatostatin (SRIF)-positive structures. Among them, n. cochlearis dorsalis and ventralis, n. ventralis lemnisci lateralis and n. parabrachialis colliculi inferioris contain huge collections of SRIF-positive neurons. Furthermore, the rat auditory system in general contains a number of SRIF-positive fibers.

Long descending projections from amygdaloid somatostatin-containing cells to the lower brain stem

Abstract The evidence of the long descending somatostatin (SRIF)- containing neuron system from the amygdaloid complex (Amy) to the lower brain stem in the rat was investigated experimentally by means of the indirect immunofluorescent technique of Coons. The destruction of the Amy resulted in a marked reduction of SRIF-containing fibers in the various areas of the lower brain stem.

Evidence for the existence of a substance P-containing pathway from the nucleus laterodorsalis tegmenti (Castaldi) to the lateral septal area of the rat.

The existence of a long ascending substance P (SP)-containing neuron system from the nucleus laterodorsalis tegmenti of Castaldi to the lateral septal area was demonstrated in this study. The destruction of the n. laterodorsalis tegmenti resulted in a marked reduction of SP-positive fibers in the ipsilateral lateral septal area.

Evidence for the existence of an enkephalin-containing pathway from the area just ventrolateral to the anterior hypothalamic nucleus to the lateral septal area of the rat

The afferent source of enkephalin-like immunoreactive (ELI) fibers in the lateral septal area of the rat was elucidated experimentally by means of an indirect immunofluorescence technique. These ELI fibers had almost completely disappeared on the operated side after the destruction of the area just ventrolateral to the anterior hypothalamic nucleus, where a number of ELI cells was detected. This fact strongly suggests that these ELI cells project ipsilaterally to the lateral septal area.