Distribution of ¹²⁵I‐galanin binding sites, immunoreactive galanin, and its coexistence with 5‐hydroxytryptamine in the cat spinal cord: Biochemical, histochemical, and experimental studies at the light and electron microscopic level

Abstract

The distribution of galanin-like immunoreactivity (GAL-LI) in the spinal cord of the cat was studied by use of indirect histochemistry and the peroxidase-antiperoxidase (PAP) technique. In the ventral horn GAL-immunoreactive (IR) axonal fibers and terminals were most frequent in the ventral part of the motor nucleus. The GAL-IR axons also contained 5-hydroxytryptamine (5-HT)-LI, and they disappeared after spinal cord transection. It was concluded that these GAL-IR fibers belong to the serotoninergic bublospinal pathway. In the medulla oblongata from normal cats, scattered GAL-IR cell bodies were encountered within the nucleus raphe obscurus and nucleus raphe pallidus. Electron microscopic observations revealed that the fine structure of the GAL-IR axonal boutons in the motor nucleus was similar to that of 5-HT-IR boutons with a varying number of immunoreactive large dense core vesicles. The postsynaptic element in all cases studied was a dendrite. A dense GAL-IR axonal plexus was found in the superficial laminae I-II of the dorsal horn. Coexistence was found between the GAL- and substance P-LI in fibers within the dorsal horn plexus. Spinal cord transection did not alter the pattern of GAL-LI in the dorsal horn, while the vast majority of GAL-IR axonal swellings disappeared following dorsal root sectioning. Electron microscopic observations in lamina II (substantia gelatinosa) revealed that the GAL-IR axonal terminals could be divided into two main groups. One with small to medium-sized axonal boutons formed synaptic contacts with both dendritic and axonal profiles. The other formed the central axon terminals of glomeruli, suggesting that GAL-LI may be present in C-type primary afferents. Numerous small GAL-IR cell bodies were encountered in laminae II and III. GAL-IR cell bodies were also observed in lamina X. The dorsal root ganglia contained a low but consistent number of small to medium-sized GAL-IR cell bodies, which all contained immunoreactive calcitonin gene-related peptide (CGRP). Following peripheral sciatic nerve transection, the number and the labeling intensity of GAL-IR cell bodies in the corresponding dorsal root ganglia showed a moderate increase. Radioimmunoassay revealed that the concentration of GAL-LI increased along the rostrocaudal axis of the normal spinal cord, and was about three times higher in the dorsal than in the ventral regions. The concentration in the dorsal root ganglia was intermediate to those seen in the corresponding dorsal and ventral cord regions.(ABSTRACT TRUNCATED AT 400 WORDS)

Galanin immunoreactivity in autonomic innervation of the cat eye

“…Specificity of immunostaining was established in control sections by omitting the primary antiserum from the incubation procedure and, in the case of GAL, by preadsorption of diluted primary antiserum with 1 kM synthetic peptide (Peninsula). The GAL antiserum is well characterized immunohistochemically; it has been used, in particular, for localization of GAL in the rat and pig eye (Stomberg et al, 1987;Stone et al, 1988) and in other organs of the cat (Kummer, 1987;Garry et al, 1989;Lindh et al, 1989;Arvidsson et al, 1991). The antisera against TH, NPY, VIP, SP, and CGRP also are commonly used immunohistochemical probes, which in this study displayed characteristic localizations fully consistent with those described in previous studies of the eye (Stone et al, 1987).…”

“…The ciliary muscle, however, is only partially depleted of GAL-positive nerves after sympathetic denervation and could be a target for GAL-containing ciliary neurons. Alternatively, expression of GAL in the moderate number of VIP-positive pterygopalatine nerve fibers supplying the ciliary muscle (Uddman et al, 1980) may account CGRP-positive, small-to medium-sized cells that express GAL (Arvidsson et al, 1991). In the anterior segment of normal eyes and eyes after sympathetic denervation, a few nerve fibers were both GAL and SP positive and, thus, of 'The results for each comparison are derived from a sample of at least 1000 cells that could be identified unambiguously in adjacent sections from three or four ganglia immunoreacted for the paired antisera.…”

“…In marsupials, GAL occurs in most sympathetic ganglion cells and in the perivascular sympathetic nerve plexus (Morris et al, 1992). In the cat, GAL localizes to many postganglionic neurons in sympathetic paravertebral ganglia (Kummer, 1987;Lindh et al, 1989) and in the parasympathetic pterygopalatine and submandibular ganglia (Lindh et al, 1989), as well as to a small number of sensory neurons in dorsal root ganglia (Garry et al, 1989;Arvidsson et al, 1991). However, relatively few GAL-positive nerve fibers have been detected in cat target tissues examined so far (Lindh et al, 1989).…”

Lumbar spinal cord neurons putatively involved in ejaculation are sexually dimorphic in early postnatal mice

“…The latter finding led to the current use of the acronym “LSt” (lumbar spino‐thalamic) when referring to this specific group, even if, to the best of our knowledge, evidence that all member neurons project to the thalamus is still missing (as acknowledged by Nicholas et al, ). Homologous populations of galaninergic neurons were also found in the cat (Arvidsson et al, ) and, recently, in humans (Chéhensse et al, ). LSt neurons are now thought to be a key component of a SGE (Clement & Giuliano, ; Veening & Coolen, ), which makes them an important target of investigation.…”

“…However, we were initially surprised to find a population of neurons in the cervical and rostral thoracic segments showing a strikingly similar distribution to that of the LSt (Figure and Figure ). Careful examination of early immunohistochemical reports on galanin revealed references to this population in the adult rat (Melander et al, ) and cat (Arvidsson et al, ). Subsequent work, starting with Ju et al (), focused on the lumbar group and its role in the control of ejaculation, and we could find no further mention of the cervical group.…”