Expression and distribution of CB1 cannabinoid receptors in the central nervous system of the African cichlid fishPelvicachromis pulcher

Abstract

Neuroanatomical investigation of the cannabinoid system in a lower vertebrate group such as teleost fishes might improve our understanding of the physiological role of such a signaling system. In the present study, the expression of a CB1 cannabinoid receptor has been demonstrated in the CNS of a teleost fish, the cichlid Pelvicachromis pulcher. Moreover, CB1-like immunoreactivity has been analyzed by using a purified antibody against the CB1 receptor amino-terminus. Immunostained neurons and varicosities were found through the telencephalon as well as in the preoptic area and lateral infundibular lobes of the hypothalamus. Stained cells were observed in the pituitary gland. Several cell bodies and nerve terminals containing an intense CB1-like immunoreactivity were found in the pretectal central nucleus and posterior tuberculum, both lying in a transitional region between diencephalon and mesencephalon. In the brainstem, the CB1 immunopositivity was more restricted than in the prosencephalon, with the exception of some large, intensely immunopositive nerve cells within the dorsal mesencephalic tegmentum, possibly motor neurons of the third cranial nerve. In the cerebellum, among a majority of immunonegative granule cells, a subset of them was immunostained. Some positive Purkinje cells were also observed. In the spinal cord, ventral gray matter, several alpha-motoneurons were stained. Similarities to and discrepancies from the CB1 receptor distributions in other vertebrate CNS are discussed, paying particular attention to the abundant CB1 immunoreactivity observed in the area encompassing the pretectum and glomerular nucleus, which is characterized by a peculiar differentiation in bony fishes.

The evolution and comparative neurobiology of endocannabinoid signalling

“…Expression is also evident in the hypothalamus and posterior tuberculum (diencephalon) and in the torus longitudinalis (mesencephalon) [90]. [86,91]. Immunostained neurons and/or fibres were observed in several brain regions, including the telencephalon, the preventricular preoptic nucleus, the lateral infundibular lobes of the hypothalamus, the pretectal central nucleus and the posterior tuberculum.…”

Endocannabinoids affect the reproductive functions in teleosts and amphibians

“…Nevertheless, although bony fish have multiple gene copies in some way related to their evolutionary radiation and phenotypic diversification, at the moment, Fugu and Solea solea (Palermo et al, submitted) are the only teleosts, among those investigated, with two CB1 receptor subtypes. Pelvicachromis pulcher (Cottone et al, 2005a), Carassius auratus (Valenti et al, 2005), Danio rerio (Lam et al, 2006) and Sparus aurata (Ruggeri et al, 2007) are in fact all provided with only one CB1 receptor subtype showing a highest sequence homology with Fugu CB1A.…”

“…The distribution of CB1 receptors has been investigated, by using specific primary antibodies against the rat CB1 (Tsou et al, 1998), in adult brains of both Pelvicachromis pulcher (Cottone et al, 2005a) and goldfish (Valenti et al, 2005), while the CB1 ontogeny was analysed in zebrafish larvae and adults by means of in situ hybridization (Lam et al, 2006). In the adult brains the CB1-likeimmunoreactivity (CB1-LI-IR) was extended through all the telencephalon and a number of CB1 immunostained cell bodies were located immediately below the ventricular ependyma, which is considered a proliferation zone in the adult fish brain (Kirsche, 1967;Ekstrőm et al, 2001;Zupanc and Zupanc, 2006).…”

“…The in situ hybridization for CB1 mRNA on zebrafish larvae brain (Lam et al, 2006) has shown an early CB1 expression in the preoptic area and, later, within the dorsal telencephalon and mesodiencephalon, brain areas rich in CB1 in the adult teleosts (Cottone et al, 2005a;Valenti et al, 2005;Lam et al, 2006). In postembryonic larvae CB1 distribution is closely resembling the adult one and the prosencephalic cannabinergic innervation is topographically related to areas interested by the concomitant differentiation of classic neurotransmitter systems (GABA, Dopamine), accordingly to what reported in the fetal brains of human and rat (Fernandez-Ruiz et al, 2004).…”

Neuroanatomical Distribution of Cannabinoid Receptor Gene Expression in the Brain of the Rough-Skinned Newt, <i>Taricha granulosa</i>

“…The neuroanatomical distribution of CB1 in mammals is well documented in the rat, primate, and canine brains [Herkenham et al, 1990;Pettit et al, 1998;Tsou et al, 1998;Ong and Mackie, 1999]. However, the distribution of CB1 in brains of non-mammals has not been studied except for one anuran amphibian, Xenopus laevis [Cesa et al, 2001;Cottone et al, 2003], and more recently, in the African cichlid fi sh, Pelvicachromis pulcher [Cottone et al, 2005].…”