Neuronal regulation of photo‐induced pineal photoreceptor proteins in carp Catla catla

Abstract

In the present in vitro study on the pineal in carp Catla catla, specific agonist and antagonists of receptors for different neuronal signals and regulators of intra-cellular Ca(++) and cAMP were used to gather basic information on the neuronal signal transduction cascade mechanisms in the photo-induced expression of rod-like opsin and alpha-transducin-like proteins in any fish pineal. Western-blot analysis followed by quantitative analysis of respective immunoblot data for both the proteins revealed that photo-induced expression of each protein was stimulated by cholinergic (both nicotinic and muscarinic) agonists and a dopaminergic antagonist, inhibited by both cholinergic antagonists and a dopaminergic agonist, but not affected by any agonists or antagonists of adrenergic (alpha(1), alpha(2) and beta(1)) receptors. Moreover, expression of each protein was stimulated by voltage gated L type calcium channel blocker, adenylate cyclase inhibitor and phosphodiesterase activator; but suppressed by the activators of both calcium channel and adenylate cyclase, and by phosphodiesterase inhibitor. Collectively, we report for the first time that both cholinergic and dopaminergic signals play an important, though antagonistic, role in the photo-induced expression of photoreceptor proteins in the fish pineal through activation of a signal transduction pathway in which both calcium and cAMP may act as the intracellular messengers.

Neural Regulation of Dark-Induced Abundance of ArylalkylamineN-Acetyltransferase (AANAT) and Melatonin in the Carp (Catla catla) Pineal: AnIn VitroStudy

“…Chronobiol Int Downloaded from informahealthcare.com by Michigan University on 11/05/14 at demonstration of neuronal signal-transduction cascade mechanisms in the photo-induced expression of photoreceptor proteins in the Catla pineal (Seth & Maitra, 2010c). In each experiment, there was a control represented by the pineal incubated under respective LD schedules in an identical medium, but in the absence of any drug.…”

“…were elevated under darkness, but suppressed in presence of light (Figure 2), provided the basis of the current in vitro study that aimed at demonstrating the neuronal mechanisms involved in the dark-and lightmediated actions on the melatonin rhythm-generating system in carp pineal using specific pharmacological agents and dosage regimens followed elsewhere for similar purpose (Denda et al, 2004;Klein et al, 1983;Kroeber et al, 2000;O'Dea & Zatz, 1976;Santanavanich et al, 2005;Schomerus et al, 2000Schomerus et al, , 2002Seth & Maitra, 2010c;Thibault et al, 1993). Since choice of a single drug and its dose in this study was strictly based on the literature, it is difficult to distinguish between physiologic versus pharmacologic effects of the drugs employed in the present and earlier studies, and the issue needs to be addressed in future study.…”

“…Level of calcium (Ca 2+ ) in the supernatants of different pineal homogenates was measured spectrophotometrically following the cresolpthalein complexone method (Young et al, 1975), using a calcium estimation kit as employed in a recent study (Seth & Maitra, 2010c). The sensitivity of the assay was 0.5-15 mg/dL.…”

“…We recently reported that cholinergic and dopaminergic, unlike adrenergic, signals play an important, though antagonistic, role in the photo-induced expression of photoreceptor proteins in the carp pineal through activation of a signal-transduction pathway in which both Ca 2+ and cAMP may act as intracellular messengers (Seth & Maitra, 2010c). However, comparable data on the neuronal regulatory mechanisms of the melatonin-generating system in any fish pineal were lacking.…”

“…From an academic point of view, Catla catla, because of its natural surface dwelling habit, maintains close contact with environmental light and, thereby, is as an excellent model for the study of photic signal-transduction mechanisms in the pineal. Since fish pineal photoreceptors in response to darkness are depolarized and allow Ca 2+ entry and cAMP accumulation (Iuvone et al, 2005), we also investigated the effects of an intracellular Ca 2+ -releasing agent, specific activator or inhibitor of Ca 2 + channel, cAMP, and regulators of intracellular cAMP on the same carp pineal as employed elsewhere (Seth & Maitra, 2010c). Additionally, the effects of proteasomal proteolysis inhibitor on AANAT band intensity were studied in the light-exposed pineal to understand the mechanisms of light actions on pineal melatonin biosynthesis.…”