Influence of melatonin on the development of functional nicotinic acetylcholine receptors in cultured chick retinal cells.

The influence of melatonin on the developmental pattern of functional nicotinic acetylcholine receptors was investigated in embryonic 8-day-old chick retinal cells in culture. The functional response to acetylcholine was measured in cultured retina cells by microphysiometry. The maximal functional response to acetylcholine increased 2.7 times between the 4th and 5th day in vitro (DIV4, DIV5), while the Bmax value for [125I]-alpha-bungarotoxin was reduced. Despite the presence of alpha8-like immunoreactivity at DIV4, functional responses mediated by alpha-bungarotoxin-sensitive nicotinic acetylcholine receptors were observed only at DIV5. Mecamylamine (100 microM) was essentially without effect at DIV4 and DIV5, while dihydro-ss-erythroidine (10-100 microM) blocked the response to acetylcholine (3.0 nM-2.0 microM) only at DIV4, with no effect at DIV5. Inhibition of melatonin receptors with the antagonist luzindole, or melatonin synthesis by stimulation of D4 dopamine receptors blocked the appearance of the alpha-bungarotoxin-sensitive response at DIV5. Therefore, alpha-bungarotoxin-sensitive receptors were expressed in retinal cells as early as at DIV4, but they reacted to acetylcholine only after DIV5. The development of an alpha-bungarotoxin-sensitive response is dependent on the production of melatonin by the retinal culture. Melatonin, which is produced in a tonic manner by this culture, and is a key hormone in the temporal organization of vertebrates, also potentiates responses mediated by alpha-bungarotoxin-sensitive receptors in rat vas deferens and cerebellum. This common pattern of action on different cell models that express alpha-bungarotoxin-sensitive receptors probably reflects a more general mechanism of regulation of these receptors.

Influence of melatonin on the development of functional nicotinic acetylcholine receptors in cultured chick retinal cells

The influence of melatonin on the developmental pattern of functional nicotinic acetylcholine receptors was investigated in embryonic 8-day-old chick retinal cells in culture. The functional response to acetylcholine was measured in cultured retina cells by microphysiometry. The maximal functional response to acetylcholine increased 2.7 times between the 4th and 5th day in vitro (DIV4, DIV5), while the Bmax value for [125I]-alpha-bungarotoxin was reduced. Despite the presence of alpha8-like immunoreactivity at DIV4, functional responses mediated by alpha-bungarotoxin-sensitive nicotinic acetylcholine receptors were observed only at DIV5. Mecamylamine (100 µM) was essentially without effect at DIV4 and DIV5, while dihydro-ß-erythroidine (10-100 µM) blocked the response to acetylcholine (3.0 nM-2.0 µM) only at DIV4, with no effect at DIV5. Inhibition of melatonin receptors with the antagonist luzindole, or melatonin synthesis by stimulation of D4 dopamine receptors blocked the appearance of the alpha-bungarotoxin-sensitive response at DIV5. Therefore, alpha-bungarotoxin-sensitive receptors were expressed in retinal cells as early as at DIV4, but they reacted to acetylcholine only after DIV5. The development of an alpha-bungarotoxin-sensitive response is dependent on the production of melatonin by the retinal culture. Melatonin, which is produced in a tonic manner by this culture, and is a key hormone in the temporal organization of vertebrates, also potentiates responses mediated by alpha-bungarotoxin-sensitive receptors in rat vas deferens and cerebellum. This common pattern of action on different cell models that express alpha-bungarotoxin-sensitive receptors probably reflects a more general mechanism of regulation of these receptors.

Developmental regulation of group III metabotropic glutamate receptors modulating adenylate cyclase activity in the avian retina.

The regulation of adenylate cyclase by neurotransmitters is observed in early development of the chick retina. In the present work we show that L-2-amine-4-phosphonobutyric acid (L-AP4), the major agonist of group III metabotropic glutamate receptors (mGluRs), inhibits the accumulation of cyclic AMP induced by forskolin in the chick retina. This effect is observed after 8 days of development (E8), is maximal from E12-E17 and decreases at the post-hatching period (PH). The inhibition is also observed in cultures of retinal cells incubated for 2-8 days. We have also investigated the interaction between group III mGluRs and other receptors coupled to adenylate cyclase in the developing retina. The inhibition by L-AP4 is partially additive with that induced by the A1 adenosine agonist Cyclohexyladenosine and is not observed when cyclic AMP levels are increased with 2-chloroadenosine or dopamine. The group II mGluR agonist trans-(1S,3R)-1-amino-cyclopentanedicarboxylic acid has an inhibitory effect only on PH retinas, indicating that group II and group III mGluRs have a differential ontogenesis in this tissue. The results show that Group III mGluRs are expressed early during chick retina development and do not interact with other receptors known to be coupled to adenylate cyclase in the developing retina.

Retinal ganglion cell distribution in the cebus monkey: a comparison with the cortical magnification factors.

The distribution of ganglion cells was determined in whole-mounted Cebus monkey retinae. Ganglion cell density along the horizontal meridian was asymmetric, being 1.2-4.3 higher in the nasal retinal region when compared to temporal retina at the same eccentricities. The total number of ganglion cells varied from 1.34 to 1.4 million. Ganglion cell density peaked at 49,000/mm2 about 0.5 mm nasal to the fovea. Comparison between ganglion cell density and areal cortical magnification factors for V1 and V2 reveals that the relative representation of the fovea increases in the visual cortex. This effect seems to be a general feature of the visual system of primates.

[Modification in the contraceptive behavior in Sorocaba in a period of 11 years (1968-1979) (author's transl)]. / Modificacoes nos habitos anticonceptionais em Sorocaba em um periodo de 11 anos (1968-1979).

PIP: 2 surveys were conducted in 1968 and 1979 in the same medium and low income neighborhood of Sorocaba, Brazil, to investigate modifications in contraceptive practice. The number of women knowing about contraception went from 68.9% to 94.6%, but the percentage of women actually using contraception decreased from 58.7% to 39.9%. Among those using contraception there was a marked increase in OC (oral contraception) use and a marked decrease in coitus interruptus and condom use. During the period of 11 years the yearly income of surveyed people had increased about 20%; however, the number of contraceptive users had increased only among women with higher income and better education, it had decreased in all other groups. The use of the pill was relatively higher among Catholic women^ieng