Rachakonda Sarojini

In vitro inhibition by dopamine of 5-hydroxytryptamine-stimulated ovarian maturation in the red swamp crayfish,Procambarus clarkii

Dopamine inhibits 5-hydroxytryptamine-stimulated maturation of the ovaries of the red swamp crayfish,Procambarus clarkii, in vitro just as it does in vivo. This in vitro inhibition appears to be due to inhibition of release of the gonad-stimulating hormone from the brain and thoracic ganglia. However, it is possible that in vivo dopamine also triggers release of the gonad-inhibiting hormone.

Cadmium chloride induced hyperglycemia in the red swamp crayfish, Procambarus clarkii: Possible role of crustacean hyperglycemic hormone

Exposure to 5 ppm cadmium chloride for up to 72-hr produces hyperglycemia in intact Procambarus clarkii, but not in eyestalkless individuals. Extracts of eyestalks, regardless of whether the eyestalks are from cadmium exposed crayfish or crayfish kept in clean water, produce a greater hyperglycemia in eyestalkless crayfish kept in clean water than in cadmium exposed eyestalkless crayfish. This difference in effectiveness of the extracts may represent a decreased responsiveness of cadmium exposed crayfish to the crustacean hyperglycemic hormone. These results support the hypothesis that cadmium induced hyperglycemia is mediated at least in part by the crustacean hyperglycemic hormone that is produced in the eyestalk.

Evidence for opioid involvement in the regulation of ovarian maturation of the fiddler crab, Uca pugilator

Abstract The potential involvement of an endogenous opioid system in the regulation of ovarian development in the fiddler crab, Uca pugilator, was investigated in vivo. Injection of the opioid, methionine enkephalin, into female crabs significantly slowed ovarian maturation in a dose-dependent manner. In contrast, injection of the opioid antagonist, naloxone, produced dose-dependent ovarian maturation. These results provide the first evidence that an opioid system is involved in the control of reproduction in a crustacean. It is hypothesized that the opioid (a) stimulates release of the gonad-inhibiting hormone, (b) inhibits release of the gonad-stimulating hormone or (c) does both (a) and (b).

An In Vitro Study of the Inhibitory Action of Methionine Enkephalin on Ovarian Maturation in the Red Swamp Crayfish, Procambarus clarkii

Abstract The possible involvement of an endogenous opioid system in the regulation of ovarian development in the red swamp crayfish, Procambarus clarkii, was investigated in vitro. Ovarian explants exposed to the opioid methionine (Met) enkephalin and thoracic ganglia showed reduced development in a dose-dependent manner as compared with explants incubated with thoracic ganglia alone. These thoracic ganglia secrete a gonad-stimulating hormone (GSH) as shown by the fact that explants incubated with thoracic ganglia alone showed more development than did explants incubated with muscle alone. On the other hand, the opioid antagonist naloxone produced dose-dependent enhanced development of explants incubated with thoracic ganglia. The fact that Met-enkephalin and naloxone are effective with thoracic ganglia in vitro strongly suggests that a functional endogenous opioid system is present in these ganglia and modulates release of GSH.

In Vivo Effects of Dopamine and Dopaminergic Antagonists on Testicular Maturation in the Red Swamp Crayfish, Procambarus clarkii

In vivo, dopamine (DA) inhibits testicular maturation in the red swamp crayfish, Procambarus clarkii. Crayfish given DA injections had a smaller testicular index, smaller testicular lobes, fewer mature sperm, and less-well-developed androgenic glands than did the control crayfish given physiological saline. Males administered 5-hydroxytryptamine (5-HT) or a DA receptor blocker, spiperone or pimozide, showed enhanced testicular maturation and more highly developed androgenic glands than did the control crayfish. When equimolar amounts of 5-HT and DA were co-injected, the actions of DA and 5-HT were found to be antagonistic. These results can be explained by assuming not only that 5-HT triggers release of the gonad-stimulating hormone (GSH) but that DA (a) triggers release of the gonad-inhibiting hormone (GIH), (b) inhibits GSH release, or

In vivo evaluation of 5-hydroxytryptamine stimulation of the testes in the fiddler crab, Uca pugilator: A presumed action on the neuroendocrine system

1. Male fiddler crabs, Uca pugilator, received injections of 5-hydroxytryptamine (5-HT, serotonin). The crabs showed dose-dependent testicular development. 2. Like 5-HT, the 5-HT releaser fenfluramine and the 5-HT potentiator fluoxetine induced testicular maturation also, but the 5-HT receptor blocker LY-53857 did not. 3. The data support the hypothesis that 5-HT exerts this stimulatory effect on the testes indirectly, by triggering release of gonad-stimulating hormone.

DOPAMINERGIC INHIBITION OF 5-HYDROXYTRYPTAMINE-STIMULATED TESTICULAR MATURATION IN THE FIDDLER CRAB, UCA PUGILATOR

The in vivo effects of dopamine (DA), a dopaminergic antagonist (spiperone), and a dopaminergic agonist (ADTN) on maturation of the testes in the fiddler crab, Uca pugilator, were determined. DA inhibited testicular maturation dose-dependently. ADTN also inhibited maturation of the testes whereas spiperone induced testicular maturation. These results provide the first evidence for dopaminergic inhibition of testicular maturation in a crustacean. This DA-induced inhibition may have been due to: (a) inhibition of release of the gonad-stimulating hormone, (b) stimulation of release of the gonad-inhibiting hormone or (c) both (a) and (b).

In vivo assessment of opioid agonists and antagonists on ovarian maturation in the red swamp crayfish, Procambarus chrkii

The possible involvement of an endogenous opioid system in the regulation of ovarian development in the red swamp crayfish, Procambarus clarkii, was investigated in vivo. Injections of the opioid, methionine (Met) enkephalin, into females significantly slowed ovarian maturation in a dose-dependent manner. In contrast, injection of the general opioid antagonist, naloxone, produced dose-dependent ovarian maturation. Furthermore, the highly selective delta opioid agonist, DADLE, also inhibited ovarian maturation, whereas a highly selective delta receptor antagonist, ICI-174,864, stimulated ovarian maturation. In view of these results and the fact that Met-enkephalin is a relatively selective delta receptor agonist, we hypothesize that in the crayfish the inhibitory effect of Met-enkephalin involves this type of binding site. Furthermore, it is hypothesized that the inhibitory action of these opioids is due to either (a) stimulation of release of the gonad-inhibiting hormone, (b) inhibition of release of the gonad-stimulating hormone or (c) both (a) and (b).

5-Hydroxytryptaminergic control of testes development through the androgenic gland in the red swamp crayfish, Procambarus clarkii

Summary The possibility that 5-hydroxytryptamine (5-HT) stimulates testicular maturation in the red swamp crayfish, Procambarus clarkii, was investigated. A series of 5-HT agonists and antagonists was used in addition to 5-HT itself. 5-HT and its agonists not only induced testicular maturation but also development of the androgenic glands. In contrast, the 5-HT antagonists had no stimulatory effects on the testes or androgenic gland. This stimulatory action of 5-HT is hypothesized to be indirect, 5-HT stimulating release of the gonad-stimulating hormone, which in turn activates the androgenic gland to synthesize and release androgenic gland hormone, and the androgenic gland hormone then triggers testicular maturation.

A possible neurotransmitter-neuroendocrine mechanism in naphthalene-induced atresia of the ovary of the red swamp crayfish, Procambarus clarkii

The ovaries in red swamp crayfish, Procambarus clarkii, exposed to 10 ppm naphthalene for 48 hr were smaller than those of crayfish kept in clean water. 5-Hydroxytryptamine stimulated ovarian maturation in naphthalene exposed crayfish after their return to clean water. Neurosecretory material accumulated in the brains and thoracic ganglia of naphthalene exposed crayfish. Extracts of brains and thoracic ganglia from naphthalene exposed crayfish were more effective in stimulating ovarian maturation than were extracts of brains and thoracic ganglia from unexposed crayfish. It is hypothesized that naphthalene inhibits release of the gonad-stimulating hormone from neuroendocrine cells in the brain and thoracic ganglia whereas 5-hydroxytryptamine stimulates release of this hormone.