Pretectal connections in turtles with special reference to the visual thalamic centers: A hodological and ?-aminobutyric acid-immunohistochemical study

Abstract

Projections of the pretectal region to forebrain and midbrain structures were examined in two species of turtles (Testudo horsfieldi and Emys orbicularis) by axonal tracing and immunocytochemical methods. Two ascending gamma-aminobutyric acid (GABA)ergic pathways to thalamic visual centers were revealed: a weak projection from the retinorecipient nucleus lentiformis mesencephali to the ipsilateral nucleus geniculatus lateralis pars dorsalis and a considerably stronger projection from the nonretinorecipient nucleus pretectalis ventralis to the nucleus rotundus. The latter is primarily ipsilateral, with a weak contralateral component. The interstitial nucleus of the tectothalamic tract is also involved in reciprocal projections of the pretectum and nucleus rotundus. In addition, the pretectal nuclei project reciprocally to the optic tectum and possibly to the telencephalic isocortical homologues. Comparison of these findings with previous work on other species reveals striking similarities between the pretectorotundal pathway in turtles and birds and in the pretectogeniculate pathway in turtles, birds, and mammals.

Projections of the nucleus lentiformis mesencephali in pigeons (Columba livia): A comparison of the morphology and distribution of neurons with different efferent projections

“…In mammals it has been shown that this projection is directed to the dorsal lateral geniculate nucleus (dLGN) and originated mainly in NOT (e.g., Graybiel and Berson,1980; Bickford et al,2000; see also Simpson et al,1988). In reptiles it has also been shown that the LM projects to the dLGN (Kenigfest et al,2000). In birds the equivalent of the LGN are the retinal‐recipient nuclei of the anterior dorsal thalamus, which includes DLL (Karten et al,1973; Karten and Shimizu,1989).…”

The nucleus pretectalis principalis: A pretectal structure hidden in the mammalian thalamus

“…In addition to birds, studies using immunohistochemistry for GABA and NPY have identified the dorsal part of the pretectal nucleus (Ptd) as the reptilian homolog to the avian PT. In addition, the reptilian Ptd further resembles the avian PT in that it is a nonretinorecipient nuclei that establishes a reciprocal connection with the TeO (Kenigfest et al, 2002;Kenigfest et al, 2000;Reiner, Brauth, Kitt, & Karten, 1980). In toads and frogs the caudal dorsal part of the so-called lateral thalamic nucleus contains NPY-ir cells that project bilaterally to the TeO (Chapman & Debski, 1995;Kozicz & Lazar, 1994).…”

Survey of oncologists' perceptions of barriers to accrual of older patients with breast carcinoma to clinical trials

“…The reciprocal projections between the PT and SC are thus likely to be important for exchanging visual and eye movement‐related information. A PTT projection has been described in frogs (Lázár, 1984, 1989; Kenigfest et al, 2000), birds (Gamlin et al, 1996), and in a variety of mammals, such as the rat (Cadusseau and Roger, 1985; Morin and Blanchard, 1998), rabbit (Holstege and Collewijn, 1982), and cat (Edwards et al, 1979). In the cat the PTT projection arises from two subnuclei of the PT, the nucleus of the optic tract (NOT) and the posterior pretectal nucleus (PPN), and primarily targets the stratum griseum superficiale (SGS) of the SC.…”