Substance P containing and cholinergic projections from the habenula

Electrolytic lesions and surgical transection of the habenulo-interpeduncular-ventrotegmental tract have established the existence of separate habenulo-interpeduncular-ventrotegmental substance P and cholinergic projections. Micro-knife lesions separating the habenula nuclei showed the medial habenular nucleus to be the source of substance P fibres running via the fasciculus retroflexus to the ventral tegmental area. The lateral habenular nucleus receives a substance P projection from the medial habenular nucleus and is the source of cholinergic projection to the interpeduncular nucleus and to the medial habenular nucleus. Lesions of the ventrotegmental-interpeduncular area did not modify the levels of substance P and choline acetyltransferase in the habenula. These observations suggested that there are no substance P or ACh containing afferents to the habenula from the ventrotegmental-interpeduncular area and the accumulation of substance P and AChE proximal to but not caudal to transections of the fasciculus retroflexus confirmed this view.

Substance P in the amygdaloid complex, bed nucleus and stria terminalis of the rat brain

Radioimmunoassay and immunohistochemical techniques have demonstrated the presence of substance P in the medial and central nuclei of the amygdala and the bed nucleus of the stria terminalis. Hemisections and micro-knife cuts transecting the anterior, posterior, medial, lateral and ventral connections to the amygdala did not modify the content of substance P in the amygdala. In addition knife cuts totally isolating the medial amygdaloid nucleus from lateral and anterior-posterior connections did not reduce the substance P content of the medial nucleus, but produced a 70% reduction in the substance P content of the central nucleus. These results suggest that substance P containing neurones in the medial and central amygdaloid nuclei do not receive substance P projections originating outside the amygdala. However, there appears to be a short substance P projection from the medial nucleus to the central nucleus.

The distribution of substance P immunoreactive fibers in the rat central nervous system

A detailed account of the distribution of immunoreactive substance P-containing structures in the rat central nervous system is presented, from results obtained by applying an indirect immunofluorescent technique. High densities of substance P-containing nerve terminals were present in sensory nuclei and other non-sensory structures such as thalamus, hypothalamus and extrapyramidal system. Substance P-reactive neuron cell bodies were present in spinal root ganglia, nucleus habenulae medialis, nucleus interpeduncularis, caudoputamen and globus pallidus. Most of the neocortex and the cerebellar cortices had no substance P-positive elements. The results support the hypothesis that substance P may be a widespread neurotransmitter in the central nervous system.

Substance P: a naturally occurring transmitter in human spinal cord

Immunoreactive substance P-like material has been found in axonal processes of human spinal cord in a location similar to that in other mammals. Substance P may be a primary sensory transmitter (or modulator) in man.