Dopaminergic modulation of the caudal photoreceptor in crayfish

Abstract

In our study we investigated the influence of dopamine (DA) on the caudal photoreceptor (CPR) in crayfish. Here we report the following: (a) the chromatographic determination of DA in the sixth abdominal ganglion (6th AG) shows a variation in the content during a 24-h cycle with the maximum value at dawn. (b) There are possibly dopaminergic neurons in the 6th AG with antityrosine hydroxylase antibodies. Immunopositive neurons (164) were located in the anterior and posterior regions of the 6th AG with the mean (± SE) diameter of their somata 23 ± 1 μm. In addition, there is immunopositive staining in axons, neuropilar fibers, and varicosities. (c) We also identified, using immunohistochemistry, 108 neurons in the sixth AG that contain dopamine D1-like receptors, with the mean (±SE) diameter of their somata 18 ± 1 μm. (d) We examined the exogenous action of DA on the electrical activity of the CPR in the isolated sixth AG by conventional extracellular-recording methods. This CPR displays spontaneous activity and phasic-tonic responses to light pulses. Topical application of dopamine to ganglia kept in the dark increased the spontaneous firing rate of the CPR, whereas the photoresponse of the CPR remained unchanged. The effect on the spontaneous activity is dose-dependent with an ED₅₀ of 33 μM, and is blocked by the dopamine D1-like antagonist SCH23390. These observations suggested that the DA is playing the role of a neurotransmitter or a neuromodulator of the CPR in the 6th AG in both species of crayfish, Procambarus clarkii and Cherax quadricarinatus.

Cyclic AMP‐regulated opposing and parallel effects of serotonin and dopamine on phototaxis in the Marmorkrebs (marbled crayfish)

“…). Before light adaptation with 10 μ m SCH23390 DA 1 receptor antagonist (Rodriguez‐Sosa et al ., ), 77.8% of the trials of DD animals showed positive phototaxis (35 of 45 trials for seven animals). After light adaptation with SCH23390, these animals still showed positive phototaxis (70%: 49 of 70 trials) (SCH23390 in Fig.…”

“…Rodriguez‐Sosa et al . (, ) also examine the role of both serotonin and dopamine in caudal photoreceptor of the crayfish terminal abdominal ganglion. Nevertheless, the interacting effects of serotonin and dopamine on phototaxis were unclear.…”

“…In crayfish, Way100635 is known as a specific 5HT 1 receptor antagonist (Spitzer et al ., ), and methiothepin and cyproheptadine are also known to act as 5HT 2 receptor antagonists (Vallas et al ., ; Spitzer et al ., ; Zhang et al ., ). Furthermore, SCH23390 is known to act as DA 1 receptor antagonist (Rodriguez‐Sosa et al ., ), and chlorpromazine and sulpiride are known to act as DA 2 receptor antagonists (Johansson & Schmidt, ; Charnetski et al ., ) in the crayfish.…”

Chronic electromyographic analysis of circadian locomotor activity in crayfish

“…Circadian rhythms have been reported in a variety of physiological functions of crayfish ranging from behavioral [37-39,41,43] to cellular [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] and molecular levels [12][13][14][15][16][17][18][19]. Many of these are thought to be under the control of endogenous circadian oscillators.…”

“…Crustaceans have been known to show circadian rhythms in hormonal secretion [12][13][14][15], neurosecretion [16], biogenic amine contents and actions in the central nervous system [17][18][19], mechanoreceptor sensitivity [20], photoreceptor sensitivity [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] and locomotor activity [37][38][39][40][41][42][43]. A previous study in the crayfish Procambarus clarkii showed that the circadian rhythm in leg movement disappeared when the circumesophageal commissures were surgically lesioned bilaterally, thus experimentally demonstrating the importance of descending signals from the brain to posterior ganglia [38].…”