Differential acetylcholinesterase activity in rat cerebrum, cerebellum and hypothalamus.

Acetylcholinesterase (AChE) has been purified from three different regions of rat brain using Sephadex G 200 column. SDS PAGE (6%) showed single band for the purified AChE fractions. Purified and lyophilized AChE from different (NH4)2SO4 precipitated fractions of three brain parts were utilized for in vitro enzyme kinetics using Dimethoate (Dmt) as inhibitor. K(m) values for cerebellum and hypothalamus were almost similar whereas cerebrum showed a different K(m) value compared to other two regions. With the drug Rivastigmine it was found that % G1 and G4 forms of AChE in three different parts of brain are different.

Effect of different gonadal states on the forskolin stimulated adenylate cyclase activity in rat brain

Forskolin-stimulated adenylate cyclase activity, measured in the hypothalamus and cerebral cortex differs in male and female rats. The gonadal steroid treatment performed induced changes in the studied adenylate cyclase activity probably in relation to the sex of the animals. The stimulated-forskolin adenylate cyclase activity in the hypothalamus from orchidectomized males showed more sensitivity than ovariectomized females. Finally, in male rats, the effects of castration on the hypothalamic enzymatic activity were partially restored by the administration of testosterone dipropionate. On the other hand, estradiol decreased the forskolin-adenylate cyclase activity in the female hypothalamus and cerebral cortex. The results show that the forskolin-stimulated adenylate cyclase activity may be related with the sex and/or the gonadal state of experimental animals.

Estradiol antagonistic effects of winter cherry extract on pituitary and hypothalamic GOPD activities

Intraperitoneal administration of an aqueous extract of winter cherry fruits [Physalis alkekengi] to adult cycling female rats diminished pituitary glucose 6-P dehydrogenase [G6PD] activity by 35% and that of the basomedial hypothalamus [BMH] by 23%. Daily doses of 1.88, 3.75, 7.5, and 15 micro g beta-estradiol administered to such animals for a period of 6-9 days increased pituitary G6PD activity by 16,30,60, and 94% and that of BMH by 14,19,30, and 52%, respectively. Combined administration of a given dose of the aqueous extract along with the above doses of beta-estradiol for 8-9 days reduced G6PD inhibitory effect of the aqueous extract on both the pituitary and BMH. In this manner the pituitary enzyme was inhibited by 14% [1.88 micro g beta-estradiol], 7% [3.75 micro g estradiol] and activated by 37% [7.5 micro g estradiol] and 62% [15 micro g estradiol]. Corresponding values for the hypothalamic enzyme were inhibitions of 21% [1.88 micro g estradiol], 18% [3.75 micro g estradiol], 7% [7.5 micro g estradiol] and activation of 2% [15 micro g estradiol]. The estrogen antagonistic effect of this aqueous extract on the brain is discussed in terms of its possible action on the inhibition of the hypothalamic gonadotropin releasing hormone and the pituitary luteinizing hormone release, thus affecting ovulation and pregnancy

Norepinephrine: stimulated activity of hypothalamic adenylate cyclase varies throughout the estrous cycle of the female rat

The activity of hypothalamic adenylate cyclase was studied throughout the estrous cycle of the female rat. The activity of the enzyme was determined in particulate fractions obtained from hypothalami of rats killed at 10.00 h and 16.00 h of the 4-day estrous cycle. The activity was assayed in the presence of norepinephrine (10(-8) to 10(-3) M) by the capacity to produce adenosine 3',5' cyclic monophosphate. The basal activity of adenylate cyclase was higher in the morning of estrus than at any other time during the cycle. Norepinephrine-stimulated adenylate cyclase activity, as assessed by the apparent affinity (Kd) and apparent maximum effect, varied during the cycle, showing highest affinity, lowest Kd, in the afternoon of proestrus. The highest level of apparent maximum effect was also found in the afternoon of proestrus declining on diestrous day 2, diestrous day 1 and estrus. The norepinephrine stimulated activity was significantly inhibited by phenoxybenzamine, an alpha-blocker, in the morning of diestrus day 1, whereas on the day of diestrus day 2 and proestrus it was inhibited by the beta-adrenoblocker, propranolol. A similar degree of inhibition by alpha- and beta-blockers was observed in the morning of estrus. These results indicate that the hypothalamic adenylate cyclase coupled to adrenergic receptors shows dynamic changes throughout the estrous cycle

Synaptosomal apyrase in the hypiothalamus of adult rats

1. The synaptosomal fraction isolated from hypothalamus of adult rats on sucrose density gradient hydrolyzes the labile phosphatase from ATP and ADP, thereby satisfying the general definition of apyrase activity. 2. The parallel behavior of ATPase and ADPase activities under different reaction conditions suggests the presence of a "true" apyrase enzyme. The optimum conditions for the are the same for both nucleotides: pH 8.0, 0.6 mM nucleotide and 1.5 mM cation. At temperatures between 10 and 40-C, both activities increase with no change in the ATP/ADP hydrolysis ratio. Thermal inactivation or inhibition of the enzyme activity by iodoacetamide, p-hydroxynercuribenzoate or 2- mercaptoethanol affected the hydrolysis of both substrates in a similar manner. 3- Adenylate Kinase and phyrophosphatase activities were not detected in the preparation. 4. The enzyme is located on the outer surface of the synaptosomal membrane: intact and lysed synaptosomes have similar activity and the supernatant obtained by centrifugation of intact synaptosomal preparations does not hydrolyze ATP or ADP