Journal of Chemical Neuroanatomy, Vol. 5:511 520 (1992)
Distribution of Somatostatin-Immunoreactivity in the Brain of the Larval Lamprey (Petromyzon marinus) Juli(tn Y4fiez, Isabel Rodviguez-Moldes and Ram6n Anad6n* Dcpartamento de Biologia Fundamental, Facultad de Biologia, Universidad de Santiago, Santiago de ('ompostcla 15706. Spain
ABSTRACT The detailed distribution of somatostatinergic neurons and fibre tracts in the brain oflarwil lamprey was studied in serially sectioned material using immunocytochemical techniques. Neurons were found to be arranged in four nuclei: a hypothalamic nucleus consisting of both small cerebrospinal fluid-contacting neurons and larger non-contacting neurons, a thalamomesencephalic nucleus and two isthmotrigeminal reticular nuclei. The hypothalamic nucleus is the first to differentiate. Analysis ot'young larvae showed that somatostatin-immunoreactivity first appeared in hypothalamic cells ( 12 mm larvae), ~hilc it appeared later in the other nuclei. The different somatostatin-immunoreactive fibre tracts innerwitc different regions of the brain. In addition, somatostatin-immunoreactive fibres originating from h x pothalamic neurons were found in the anterior neurohypophysis, which suggests the presence of a hy pothalamohypophysial somatostatinergic system in lampreys. Kl'~'wo~ns:
Somatostatin lmmunohistochemistry Neurohypophysis
INTRODUCTION Somatostatin appeared early in vertebrate phylogeny and its tetradecapeptide sequence has been conserved throughout evolution (Vale et al., 1976: King and Millar, 1979; Dubois, 1981 ), although certain fish have two different genes for somatostatin (see Andrews et al., 1988). Andrews et al. (1988) reported the homologous substitution of serine for threonine in position 12 of somatostatin-14 in lamprey, lmmunohistochemical and radioimmunoassay studies have determined the distribution of somatostatin-14 in the gut, pancreas and central ncrvous system of the different vertebrate classes (Vale et al., 1976: Van Noorden et al., 1977; Stewart et al., 1978: King and Millar, 1979; Seino et al., 1979; Andrews el al., 1987; Elliot and Youson, 1987). Somatostatinergic neurons and fibres have been described in the hypothalamohypophysial systems of tish (Dubois et al., 1979; Olivereau et al., 1984b; Batten el a/., 1985: Moons el al., 1989; Chiba et al., 1989; Sas lind Maler, 1991), amphibians (Vandesande and Dierickx, 1980; Dierickx et al., 198 I: Fasolo and Gaudino, 1981; Yui, 1982; Blfihser el al., 1982: Olivereau el al., 1987), reptiles (Goosens el al., 1980: Fasolo and Gaudino, 1982), birds (Takatsuki et al., 1981) and mammals (Krisch, 1978; Dierickx and Vandesande, 1979; *Addrcsscorrespondencelo: Dr Ram6n Anaddn, Departamento dc Biologia Fundamental. Facultad de Biologia, Santiago de ('ornposlela 15706, Spain. 0891 0618/92/060511 10510.00 © 1992 bv John Wiley and Sons Ltd
Neuronal distribution
Nerve pathways
Richoux and Dubois, 1980; Finley uf a/., 1981: Shimada and lshikawa, 1989), suggesting a role in hypophysiotrophic regulation. S o m a t o s t a t i n - 14-immunoreactivc ISOM-ir) neurons and fibres have been also t\mnd in extrahypothalamic areas, suggesting a neuromodulatory and/or neurotransmitter role for this peptide. Some information about somatostatmergic nuclei and pathways is now available l\~r mammals (Krisch, 1978, 1981; Richoux lind Dubois, 1980), but very few studies have been carried out in nonmammalia (Goosens el al., 1980: Sas and Maler, 1991). The distribution of SOM-ir neurons and libres has already been described in the adult himprey spinal cord (Buchanan et al., 1987) as well as in the brain of both adult and larval lamprey (Nozaki ut al.. 1984; Wright, 1986; Cheung eta/., 199(I). Fibre pathways, however, have not been accurately mapped. Interestingly, although the neurohypophysis of adult lamprey has been reported to be a target for fibre systems immunoreactive to luteinizing hormone-releasing hormone, wisopressin and substance-P, it is not a target for SOM-ir systems (Nozaki et al., 1984). Since it has been reported that SOM-ir distribution is similar in larwll and aduh lamprey (Wright, 1986), analysis ofthcsc systems in the larval brain can be extrapolated to the species as a whole. Furthermore, the study of small larvac offers unique opportunities tk~r tracing the difl'erentiation of the neuronal nuclei. Previous studies of the
512
J. Yfifiez et al. a I
.
b I
7.,s. R. (1977). The brain of lamprey m a c o m p a r a l i \ e perspective. ,4#m. N Y ,4cad. Set. 229,
Distribution of Somatostatin-Immunoreactivity in the Brain of the Larval Lamprey (Petromyzon marinus) Juli(tn Y4fiez, Isabel Rodviguez-Moldes and Ram6n Anad6n* Dcpartamento de Biologia Fundamental, Facultad de Biologia, Universidad de Santiago, Santiago de ('ompostcla 15706. Spain
ABSTRACT The detailed distribution of somatostatinergic neurons and fibre tracts in the brain oflarwil lamprey was studied in serially sectioned material using immunocytochemical techniques. Neurons were found to be arranged in four nuclei: a hypothalamic nucleus consisting of both small cerebrospinal fluid-contacting neurons and larger non-contacting neurons, a thalamomesencephalic nucleus and two isthmotrigeminal reticular nuclei. The hypothalamic nucleus is the first to differentiate. Analysis ot'young larvae showed that somatostatin-immunoreactivity first appeared in hypothalamic cells ( 12 mm larvae), ~hilc it appeared later in the other nuclei. The different somatostatin-immunoreactive fibre tracts innerwitc different regions of the brain. In addition, somatostatin-immunoreactive fibres originating from h x pothalamic neurons were found in the anterior neurohypophysis, which suggests the presence of a hy pothalamohypophysial somatostatinergic system in lampreys. Kl'~'wo~ns:
Somatostatin lmmunohistochemistry Neurohypophysis
INTRODUCTION Somatostatin appeared early in vertebrate phylogeny and its tetradecapeptide sequence has been conserved throughout evolution (Vale et al., 1976: King and Millar, 1979; Dubois, 1981 ), although certain fish have two different genes for somatostatin (see Andrews et al., 1988). Andrews et al. (1988) reported the homologous substitution of serine for threonine in position 12 of somatostatin-14 in lamprey, lmmunohistochemical and radioimmunoassay studies have determined the distribution of somatostatin-14 in the gut, pancreas and central ncrvous system of the different vertebrate classes (Vale et al., 1976: Van Noorden et al., 1977; Stewart et al., 1978: King and Millar, 1979; Seino et al., 1979; Andrews el al., 1987; Elliot and Youson, 1987). Somatostatinergic neurons and fibres have been described in the hypothalamohypophysial systems of tish (Dubois et al., 1979; Olivereau et al., 1984b; Batten el a/., 1985: Moons el al., 1989; Chiba et al., 1989; Sas lind Maler, 1991), amphibians (Vandesande and Dierickx, 1980; Dierickx et al., 198 I: Fasolo and Gaudino, 1981; Yui, 1982; Blfihser el al., 1982: Olivereau el al., 1987), reptiles (Goosens el al., 1980: Fasolo and Gaudino, 1982), birds (Takatsuki et al., 1981) and mammals (Krisch, 1978; Dierickx and Vandesande, 1979; *Addrcsscorrespondencelo: Dr Ram6n Anaddn, Departamento dc Biologia Fundamental. Facultad de Biologia, Santiago de ('ornposlela 15706, Spain. 0891 0618/92/060511 10510.00 © 1992 bv John Wiley and Sons Ltd
Neuronal distribution
Nerve pathways
Richoux and Dubois, 1980; Finley uf a/., 1981: Shimada and lshikawa, 1989), suggesting a role in hypophysiotrophic regulation. S o m a t o s t a t i n - 14-immunoreactivc ISOM-ir) neurons and fibres have been also t\mnd in extrahypothalamic areas, suggesting a neuromodulatory and/or neurotransmitter role for this peptide. Some information about somatostatmergic nuclei and pathways is now available l\~r mammals (Krisch, 1978, 1981; Richoux lind Dubois, 1980), but very few studies have been carried out in nonmammalia (Goosens el al., 1980: Sas and Maler, 1991). The distribution of SOM-ir neurons and libres has already been described in the adult himprey spinal cord (Buchanan et al., 1987) as well as in the brain of both adult and larval lamprey (Nozaki ut al.. 1984; Wright, 1986; Cheung eta/., 199(I). Fibre pathways, however, have not been accurately mapped. Interestingly, although the neurohypophysis of adult lamprey has been reported to be a target for fibre systems immunoreactive to luteinizing hormone-releasing hormone, wisopressin and substance-P, it is not a target for SOM-ir systems (Nozaki et al., 1984). Since it has been reported that SOM-ir distribution is similar in larwll and aduh lamprey (Wright, 1986), analysis ofthcsc systems in the larval brain can be extrapolated to the species as a whole. Furthermore, the study of small larvac offers unique opportunities tk~r tracing the difl'erentiation of the neuronal nuclei. Previous studies of the
512
J. Yfifiez et al. a I
.
b I
7.,s. R. (1977). The brain of lamprey m a c o m p a r a l i \ e perspective. ,4#m. N Y ,4cad. Set. 229,
